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= February 8 =
== Pinhole ==
= August 19 =
A single [[pinhole lens]] provides a single, dim image with an infinite field of focus. So:
== Is the speed of light constant, when measured by a '''remote inertial''' observer, who '''non-locally''' measures a photon traveling a long way in a '''curved''' vacuum? ==
1) Can multiple pinhole images be combined to create a single, bright image of infinite focus, using either mirrors to combine the images or electronic image capture from each pinhole to combine them ?
I'm asking, because our article [[speed of light]] states confusingly: {{tq|'''"In non-inertial frames of reference (gravitationally curved spacetime or accelerated reference frames)'''...the speed of light can differ from c when measured from a remote frame of reference".}} This sentence seems to ignore the situation I'm asking about, when the remote observer's frame of reference is '''inertial''', but the spacetime the light travels through is '''curved'''. [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 08:32, 19 August 2025 (UTC)
2) Or, if combining all those slightly different images leads to a fuzzy image, could [[adaptive optics]] be used to restore the composite image to a perfect focus ? [[User:StuRat|StuRat]] ([[User talk:StuRat|talk]]) 04:05, 8 February 2011 (UTC)
:The length traveled by a photo should be the path length as measured along its curved trajectory, a geodesic of the manifold that is spacetime. I am not sure how you propose the stationary observer is going to measure this. It is in fact not even clear how to ''define'' the path length (in the mathematical model of [[curved spacetime]], a [[Lorentzian manifold]]) with respect to a ''given'', fixed frame of reference. [[Inertial frames of reference]] are useful in special relativity, when objects not acted upon by a force travel in straight lines. Space curvature means that there are no "straight lines", so the inertial model for establishing a reference frame breaks down. ​‑‑[[User talk:Lambiam#top|Lambiam]] 14:07, 19 August 2025 (UTC)
:Pinhole lenses are pretty much poor-man's optics. If you're already going to use mirrors/lenses/digital processing to resolve an image, it seems that the pinhole becomes pragmaticly worthless. I suppose you could technically do all of the above, but it strikes me as rather pointless to use a lens or mirror to focus multiple pinhole images into a brighter image where the lens or mirror itself would do the job better by itself... --[[User:Jayron32|<font style="color:#000099">Jayron</font>]]'''''[[User talk:Jayron32|<font style="color:#009900">32</font>]]''''' 04:11, 8 February 2011 (UTC)
::Let's assume we (as inertial observers) see a photon travel near the sun in a curved trajectory. Do you claim we can't use any tool (e.g. a telescope or whatever) for measuring the length of this photon's curved trajectory? [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 15:59, 19 August 2025 (UTC)
:::<small>I think this was a physics question, not an engineering question. [[User:Ariel.|Ariel.]] ([[User talk:Ariel.|talk]]) 05:34, 8 February 2011 (UTC)</small>
:::We can detect only photons that arrive at our ___location. If a remote photon interacts with something else in such a way as to cause emission of another photon in our direction, we can detect the resulting photon but we're not directly observing the trajectory of the initial one.
:::Also, there are ideas to image distant planets using an enormous pinhole camera. http://www.universetoday.com/9934/biggest-pinhole-camera-ever/ [[User:Ariel.|Ariel.]] ([[User talk:Ariel.|talk]]) 05:38, 8 February 2011 (UTC)
::::Actually,Saying despite"what theif article'sas name,remote Iobservers don't think that'swe reallysee a pinholephoton camera.travel It's basically an artificial eclipse, which screens outnear the parentsun" staris solike thatsaying the"what planetif can beas seenfans withwatching a telescope.soccer match Itfrom looks10 tomiles meaway, likewe itget ishit ''not''by athe deviceball meanton toits createway anfrom imagethe somewhereplayers basedfoot onto the physicalgoal". separation ofA raysremote withobserver differentcan't anglesobserve asa theyphoton's passtrajectory. through the pinhole.-- [[User:WntAvocado|WntAvocado]] ([[User talk:WntAvocado|talk]]) 0117:0149, 919 FebruaryAugust 20112025 (UTC)
::::So what does the quote (from Wikipedia) in my original post mean, about when c is "measured from a remote frame of reference"? Doesn't the measurement of c made by a remote observer, mean measuring the ratio between, the photon's trajectory measured by that remote observer, and the time it takes the photon to travel this trajectory - when this time is measured by that remote observer? [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 18:29, 19 August 2025 (UTC)
::The multiple pinholes would have different points of view, so their combined image via mirrors would inevitably be blurred, if there is anything in the foreground and if the pinholes are any distance apart. And a pinhole image is inherently blurry, not at all of "infinite focus." It is more of "no focus." It's just that nearby and distant objects are equally blurry, with the blur circles related to the size of the pinhole. A large pinhole lets in more light but has more blur. A very small pinhole has more diffraction. There is an optimum, as discussed in books by Ansel Adams. I have made pinhole images on photographic paper, then scanned the (negative) image, reversed it via Photoshop, and sharpened it via Photoshop, resulting in a very pleasing image. Photographic paper or film does a nice job of integrating photons over an extended exposure. [[User:Edison|Edison]] ([[User talk:Edison|talk]]) 04:49, 8 February 2011 (UTC)
:::::I'm not a physicist nor the person who wrote the article. I would assume that we can know the time of the photon's origin based on whatever caused it to be emitted also having other effects (gravitational waves, other photons, etc) that reach us directly. And that we can measure the time of the photon's arrival at another point based on the effects of its arrival (reflected or re-emitted light, for instance) that reach us directly. And that we can thus measure the time elapsed between departure and arrival and deduce its speed. But we can't observe its trajectory, only infer it. -- [[User:Avocado|Avocado]] ([[User talk:Avocado|talk]]) 20:15, 19 August 2025 (UTC)
::::::Please note that the condition of "local measurement" (as opposed to "non-local" one) is a well known requirement for the speed of light to be constant. I've asked whether the requirement of locallity of measurement is also needed when the observer's frame of referenece is inertial. [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 06:47, 20 August 2025 (UTC)
:You can imagine that you have a torch in your hand and point it towards a remote black hole. The light from the torch will travel in the direction of the event horizons but will never cross it (from the point of view of an external inertial observer). This effectively means that the speed of light becomes zero in the vicinity of the horizon. However the proper speed of light will remain ''c'' of course. [[User:Ruslik0|Ruslik]]_[[User Talk:Ruslik0|<span style="color:red">Zero</span>]] 20:33, 19 August 2025 (UTC)
::When a photon is approaching a black hole, both the distance traveled by the photon, and the time it takes the photon to travel that distance, approach infinity (from the inertial observer's viewpoint), so the "effective" velocity becomes meaningless rather than "zero". [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 06:47, 20 August 2025 (UTC)
:::Sorry, but the distance cannot become infinite because it is a known quantity. Indeed, you can measure the distance to the black hole and its mass and then calculate the distance to the horizon from the observer.
:::I think there may be some miscommunication here. In the limit of a hole of width zero, StuRat is quite correct that a pinhole image has perfect focus regardless of the ___location of the target (but also zero brightness). And it is indeed possible to reconstruct a scene from an image formed using multiple pinholes -- there is a substantial literature on "multiple-pinhole image reconstruction". The technique is particularly useful for images formed using types of radiation for which no good lenses or mirrors exist. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 05:17, 8 February 2011 (UTC)
::::If the goal here is to create an image with infinite depth of field, I think a simpler solution would be to use a traditional camera and [[focus stacking]]. --[[User:Daniel J. Leivick|<span style="text-shadow:#BBBBBB 0.2em 0.2em 0.1em; class=texhtml">Daniel</span>]] 05:21, 8 February 2011 (UTC)
::::Edison is correct. In the limit of zero width the image becomes blurry. [[User:Dauto|Dauto]] ([[User talk:Dauto|talk]]) 05:28, 8 February 2011 (UTC)
:::Actually there is no need to use black holes at all. You can put a mirror on the Earth's surface and direct the laser beam at it from a remote ___location in space. Then since you know the distance and can measure the time when the reflected signal comes back you can calculate the speed by dividing the first quantity by the second. The result will be that the (apparent) speed of light is less than ''c''. [[User:Ruslik0|Ruslik]]_[[User Talk:Ruslik0|<span style="color:red">Zero</span>]] 10:39, 20 August 2025 (UTC)
== Anti-Histamines + Zantac ==
::::I can see some practical issues with measuring the distance to a black hole. And also some theoretical issues. ​‑‑[[User talk:Lambiam#top|Lambiam]] 16:53, 20 August 2025 (UTC)
:::::Any black hole is just a mass. You need only to measure the orbital parameters of test particles moving around it. [[User:Ruslik0|Ruslik]]_[[User Talk:Ruslik0|<span style="color:red">Zero</span>]] 17:34, 20 August 2025 (UTC)
::This is far from the first time I have been exposed to these facts, but this concept still breaks my brain a little. I think it's on account of how we utilize the notion of an observer from an outside frame of reference as an abstraction. Obviously, in terms actual empirical observation at this point, the photon is completely red-shifted and has no chance of ever escaping. So it can't ever be directly observed. And yet we regard it as being unable to ever being able to be observed to have crossed the event horizon. Can someone help me with the structural distinction here? Because obviously if we had a photon's trajectory bent around the gravity well of a black hole (or any mass), we could observe it only by directly interacting with it by intercepting it somewhere along its path. So what do we mean when we talk about observation in an instance that is not in any scenario actually physically possible? ''[[User:Snow Rise|<b style="color:#19a0fd;">S</b><b style="color:#66c0fd">n</b><b style="color:#99d5fe;">o</b><b style="color:#b2dffe;">w</b><b style="color:#B27EB2;">Rise</b>]][[User talk:Snow Rise|<sup><b style="color:#d4143a"> let's rap</b></sup>]]'' 06:44, 24 August 2025 (UTC)
:::Just a small remark: '''<span style="color: red">"red-shifted"</span>''' (as you say), only when it tries to ''escape'' a black hole, but here we are talking about a photon ''approaching'' a black hole, so it's '''<span style="color: blue">blue-shifted</span>'''. [[Special:Contributions/2A06:C701:745A:B800:B559:3320:A4F4:C460|2A06:C701:745A:B800:B559:3320:A4F4:C460]] ([[User talk:2A06:C701:745A:B800:B559:3320:A4F4:C460|talk]]) 10:22, 24 August 2025 (UTC)
:::Regardless of their colour (frequency), photons can only be directly observed when they hit the observer. This was already pointed out above by Avocado. They can only be observed, directly or indirectly, when they are detected by some detector, which means in quantum terminology that they are "[[Measurement in quantum mechanics|measure]]d". Measurement of a photon means a change in a macroscopic system (a [[photoreceptor cell]] in the observer's eye, a [[photographic plate]] or [[photographic film|film]], a [[photodetector]], ...) as the result of an interaction with that system. Unless the measuring system is close to where the photon is, the probability of an interaction taking place is vanishingly small. ​‑‑[[User talk:Lambiam#top|Lambiam]] 12:05, 24 August 2025 (UTC)
::::Do you claim, any measurement (e.g. by a telescope or whatever) of the length of a photon's curved trajectory - whether near the sun - or in any phenomenon of gravitational lensing, is a local measurement? [[User:HOTmag|HOTmag]] ([[User talk:HOTmag|talk]]) 13:11, 24 August 2025 (UTC)
:::::Does [[Principle of locality]] help? {The poster formerly known as 87.81.230.195} [[Special:Contributions/90.210.150.115|90.210.150.115]] ([[User talk:90.210.150.115|talk]]) 18:03, 24 August 2025 (UTC)
::::I think you've mis-interpeted my inquiry here, {{u|Lambiam}}. As it happens, I'm a bit of an expert in visual cognition, and so very familiar with the physics/biophysics of photoreceptive media. That's not the part I am struggling to fix in my mind here. My epistemological confusion about the terminology is this: since a photon trapped at the event horizon never escapes to interact with such a medium, what do we mean when we talk about "observation" when, for example {{u|Ruslik0}} says {{tq|The light from the torch will travel in the direction of the event horizons but will never cross it (from the point of view of an external inertial observer).}}? Is it a conceptual conceit/misnomer for describing the relation of the frames of reference? If so, can you think of a thought experiment that would explain those interactions in such a way that accounts for the fact that, as a strictly empirical and ontological matter, no observation at a distance can be made? Maybe Ruslik0 just mixed their metaphors and terminology a bit? If not, I'm super confused as to what the act of observation means in that description. ''[[User:Snow Rise|<b style="color:#19a0fd;">S</b><b style="color:#66c0fd">n</b><b style="color:#99d5fe;">o</b><b style="color:#b2dffe;">w</b><b style="color:#B27EB2;">Rise</b>]][[User talk:Snow Rise|<sup><b style="color:#d4143a"> let's rap</b></sup>]]'' 22:10, 24 August 2025 (UTC)
:::::You are right, I misunderstood the essence of your post. My reaction was triggered by the statement connecting our inability to observe the photon to its colour, which is I think essentially correct – in the model its wavelength tends to zero as it approaches the event horizon – but irrelevant. Scenario's of a photon traveling to an event horizon can be described that conform to a mathematical model of GR, such as [[Schwarzschild metric|Schwarzschild's exact solution to Einstein's equations]]. Such descriptions need a frame of reference, preferably one that in the limit, away from the mass, is an inertial frame. I too think the wording of these scenario's is sometimes confused. The scenario may include an observer for which this frame is stationary who can observe phenomena as predicted by the model, which in real life would validate the model. But such observation can only be through information that reaches them from afar, such as transmitted by electromagnetic waves. An astronaut approaching the event horizon might broadcast a livestream witness report that reaches the observer, but a photon can do no such thing. The models do not allow an observer to observe the unfolding of the scenario with regard to the traveling photon, so describing the scenario in terms of observations is confused. ​‑‑[[User talk:Lambiam#top|Lambiam]] 23:58, 24 August 2025 (UTC)
:::::What I actually meant is [[shapiro time delay]], which can be interpreted as slowing of light in presence of a gravitational field. [[User:Ruslik0|Ruslik]]_[[User Talk:Ruslik0|<span style="color:red">Zero</span>]] 20:33, 25 August 2025 (UTC)
= August 26 =
Is there a reason why no drug company has marketed a anti-histamine such as Allegra (H1 blocker) + Zantac (H2 blocker) in one pill? I have patients with serious hives taking it and I hear it works much better than an anti-histamine alone. Would Zantac alone help also? <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/76.169.33.234|76.169.33.234]] ([[User talk:76.169.33.234|talk]]) 08:05, 8 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:We do not give medical advice. And, yeah, that's it. --[[User:Ouro|Ouro]] <small>([[User_talk:Ouro|blah blah]])</small> 12:30, 8 February 2011 (UTC)
== Pharmacology ==
:Perhaps drug companies think that such pills will become cheaper than the price of the two separate pills. [[User:Count Iblis|Count Iblis]] 14:11, 8 February 2011 (UTC)
A friend once mentioned a book similar to an Encyclopedia, describing background events behind the development of many well known medicines . Please inform if a similar book can be found and how to "custom search" at any of the sites of WIKI for such a book .
: I think we can answer parts of this question without violating the med advice restriction.
Thnx [[User:Dr chifti|Dr chifti]] ([[User talk:Dr chifti|talk]]) 05:05, 26 August 2025 (UTC)
:*The first question "Is there a reason why no drug company has marketed..." is probably simply because the combination of [[Histamine H1 receptor|H1]] and [[Histamine H2 receptor|H2]] blockers hasn't been proven to be efficacious and the [[FDA]] (presuming this is referring to the US) has not approved the use of [[H2 antagonists]] for this purpose. If a well designed [[randomized controlled trial]] demonstrated that a combination drug was superior to the single drug standard of care, it would probably be marketed quickly to replace the old stand-bys. And I doubt that it would be cheaper -- they would come up with a fancy name like Zanyryx XR (lots of x's, y's, and z's means its a really good drug), package it up in a nice box, spend gazillions on marketing to convince the general public to "ask your doctor how Zanyryx can help you" and quadruple the price of the two individual components. Who wants to take two separate pills when you can take just one!
:You might find such a work used as one of the many references for the article [[History of medicine]], athough what you describe would be a [[Tertiary source]] (like Wikipedia itself) rather than a [[Secondary source]] which Wikipedia prefers for article sources.
:*With regard to the last question "Would Zantac alone help also?" we can't really say for any given patient whether [[ranitidine]] would be helpful, but for general information about this topic we can point the OP towards references ([http://www.ncbi.nlm.nih.gov/pubmed/11702618] and [http://www.ncbi.nlm.nih.gov/pubmed/12113219]) the latter of which says: "An H2-antihistamine administered concurrently with an H1-antihistamine may modestly enhance relief of itching and wheal formation in some patients with urticaria refractory to treatment with an H1-antihistamine alone. The available evidence does not justify the routine addition of H2-antihistamine treatment to H1-antihistamine treatment."
:Searching Wikipedia for the term "Encyclopedia of pharmacology" led me to the article ''[[Pharmacology Research & Perspectives]]'' whch uses as its reference 4 ''The Sage Encyclopedia of Pharmacology and Society'' – see that article for its bibilographical details. {The poster formerly known as 87.81.230.195} [[Special:Contributions/90.210.150.115|90.210.150.115]] ([[User talk:90.210.150.115|talk]]) 08:04, 26 August 2025 (UTC)
: Does that help? --- [[User:Medical geneticist|Medical geneticist]] ([[User talk:Medical geneticist|talk]]) 14:45, 8 February 2011 (UTC)
:Searching Archive.org for [https://archive.org/search?query=history+of+medicines history of medicines] turns up many candidates, including [https://archive.org/details/ourmodernmedicin0000band/page/n7/mode/2up?view=theater Our Modern Medicines] (F Bandelin, 1986) which seems to match your description. <span class="nowrap">[[User:Verbarson|-- Verbarson ]] <sup>[[User talk:Verbarson|talk]]</sup><sub>[[Special:Contributions/Verbarson|edits]]</sub></span> 15:04, 26 August 2025 (UTC)
= August 27 =
:My guess is that the biggest reason you don't see an [[Allegra]]/[[Zantac]] combo pill (at least in the US) is that Allegra was approved for treatment of allergies, and Zantac was approved for treatment of stomach issues. Although doctors are free to prescribe drugs for off-label use once they are approved, the FDA has some pretty stringent rules on ''marketing'' drugs for off-label use. Who would you "officially" sell the combo pill to? People with both allergies and acid reflux? Combo pills like [[Ezetimibe/simvastatin]] (Vytorin) and amoxicillin/clavulanic acid ([[Augmentin]]) are sold because both drugs treat the same condition. A pill for treatment of two different conditions doesn't have as large a market (and you can't sell it to treat a single condition, because the drugs aren't approved to treat a single condition). ''Even if'' the combo does better than one drug alone, the FDA (or insert-country-specific-regulatory-agency) wouldn't approve it until you did a clinical trial to show that it did. That's a massive expenditure of cash for drugs which are off patent, even if prior approval means you can skip most of the safety stages. -- [[Special:Contributions/174.24.195.38|174.24.195.38]] ([[User talk:174.24.195.38|talk]]) 16:22, 8 February 2011 (UTC)
== [[Lorentz factor]] derivarion ==
::Thanks for the answers. I don't really see how this is medical advice and it kind of irritates me how a lot of times when people ask questions that aren't really medical advice, its considered that. I work in a pharmacy and have seen the combination recommended more than once. I know it wouldn't be cheaper, but drug companies are always looking to make more money. For example, they combined Imitrex which is now available in generic with aleve to make a new migraine drug just to make a new brand name drug. Aleve isn't used to treat migraines, if anything, it can treat minor headaches at the most. <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/76.169.33.234|76.169.33.234]] ([[User talk:76.169.33.234|talk]]) 05:57, 9 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
In '''[[special relativity]]''', a common way to derive the '''Lorentz factor''' <math>\gamma</math> is via the '''[[pythagorean theorem]]''', without using the complicated '''[[Lorentz transformations]]''' (which I myself have yet to study).
:::What you are seeing is called "[[off-label use]]" as implied by user 174.24.195.38, when doctors prescribe a drug that is FDA approved for one use but is found by the medical community to be useful for something else. This practice is part of the discretion that a physician has in treating patients, but it is a little risky to prescribe a drug for something that has not been rigorously proven beneficial. <small>p.s. the reason your question got flagged as possible med advice is that you mentioned a very specific patient scenario, about which we cannot give information</small> --- [[User:Medical geneticist|Medical geneticist]] ([[User talk:Medical geneticist|talk]]) 12:09, 9 February 2011 (UTC)
By the equation
== What causes you to want to stretch in the morning? ==
:<math>(c\,{\rm T_s})^2=(v\,{\rm T_s})^2+(c\,{\rm T_v})^2</math>,
such that
:<math>c</math> [[speed of light]] in a vaccum
:<math>v</math> speed of a '''moving observer''' relative to a '''stationary observer'''
:<math>{\rm T_s}</math> stationary observer time
:<math>{\rm T_v}</math> moving observer time
hence
:<math>\gamma=\frac{\rm T_s}{\rm T_v}=\frac{1}{\sqrt{1-\big(\frac{v}{c}\big)^2}}</math>
My questions are as follows:
#Is this derivation actually legitimate, or does it contain any non-proven hidden assumptions?
#I have not yet seen any '''mathematical reasoning''' showing these transformations must be [[Linear map|'''linear''']].<br>In my humble opinion, most sources completely ignore this point, or treat it superficially at most.<br>I would like to know if there is any such reasoning.
#Why is the factor not written <math>\gamma(v)</math>?
[[User:יהודה שמחה ולדמן|יהודה שמחה ולדמן]] ([[User talk:יהודה שמחה ולדמן|talk]]) 15:29, 27 August 2025 (UTC)
:It is not clear where the first equation comes from. [[User:Ruslik0|Ruslik]]_[[User Talk:Ruslik0|<span style="color:red">Zero</span>]] 20:25, 27 August 2025 (UTC)
::Watch this short video [https://www.youtube.com/watch?v=67xr6EZEYV8 '''here''']. It is very common. [[User:יהודה שמחה ולדמן|יהודה שמחה ולדמן]] ([[User talk:יהודה שמחה ולדמן|talk]]) 04:11, 28 August 2025 (UTC)
:::That the equation is common doesn't mean it's clear where it comes from. It's not a priori clear that in a triangle with edges <math>cT_s</math>, <math>vT_s</math> and <math>cT_v</math> the latter two edges must be perpendicular. When I learned about special relativity, it started with the Lorentz transformations. Those aren't terribly hard; this was my first week at university. It could be done in the last year of secondary school. [[User:PiusImpavidus|PiusImpavidus]] ([[User talk:PiusImpavidus|talk]]) 09:14, 28 August 2025 (UTC)
:It's worth highlighting that the 4-space Lorenz transformations take place in is non-Euclidian. So it doesn't use the Euclidian metric, normally calculated with Pythagoras's theorem. Instead it uses a version with the squares of the three length components added but the time component subtracted.
:If you eliminate two of the length components this looks like a difference of squares. Rearrange these you get a sum and it looks like Pythagoras's theorem, but because it's been rearranged it isn't really the same thing. The minus sign in the the second expression more correctly expresses the metric. --[[Special:Contributions/217.23.224.20|217.23.224.20]] ([[User talk:217.23.224.20|talk]]) 10:38, 28 August 2025 (UTC)
:It is not clear who introduced the convention of using the Greek letter <math>\gamma</math> for the Lorentz factor (not Lorentz himself, nor Einstein, who used the letter <math>\beta</math> in "Zur Elektrodynamik bewegter Körper"*), but since it tends to be all over the place in derivations in special relativity, the one-letter notation is obviously more convenient than writing each time <math>\gamma(v)</math>. ​‑‑[[User talk:Lambiam#top|Lambiam]] 10:41, 28 August 2025 (UTC)
:<hr style="width:5em">
:{{*}}{{small|Perhaps [[Hans Bethe|Bethe]] in [https://link.springer.com/chapter/10.1007/978-3-642-52619-0_3 "Quantenmechanik der Ein- und Zwei-Elektronenprobleme" (1933)]. This is behind a paywall; I cannot check if he actually used this notation. ​‑‑[[User talk:Lambiam#top|Lambiam]] 11:08, 28 August 2025 (UTC)}}
::Bethe uses <math>\varepsilon = E/E_0</math> (his eq. 9.16; <math>E_0</math> is the rest energy), which is the Lorentz factor; I don't think he expresses it in terms of ''v'' and ''c'' anywhere. (Accessed via Wikipedia Library, which once again proved more powerful than my university account...). --[[User:Wrongfilter|Wrongfilter]] ([[User talk:Wrongfilter|talk]]) 11:34, 28 August 2025 (UTC)
'''To point 3:''' Writing <math>\gamma(v)</math> declares only that <math>\gamma</math> is a function of a variable <math>v</math> thus <math>\gamma = \gamma(v)</math>
What causes you to want to stretch in the morning? It seems as though it is almost an involuntary action, or at least that you would be very silly to resist the urge when it comes. I am looking for a reason on some molecular or cellular level if possible.
which is true but conceals the nature of the function. Lorentz factor <math>\gamma</math> is a dimensionless ratio that is a non-linear function of a velocity <math>v</math> that for any real mass is constrained to be less than <math>c</math>. For a massless particle such as a photon, calculating <strike>a unity</strike>an infinite Lorentz factor adds no useful information.
'''To point 2:''' Given the Lorentz equation confirmed in Special relativity
:<math>\gamma=\frac{1}{\sqrt{1-\big(\frac{v}{c}\big)^2}}</math>
the OP chooses by algebraic reasoning to derive an arbitrary relation
:<math>(c\,{\rm T_s})^2=(v\,{\rm T_s})^2+(c\,{\rm T_v})^2</math>
but this result is flawed. It predicates two different observers each of whom would have to be moving at c, as only a photon can, if expressions
<math>(c\,{\rm T_s})</math> and <math>(c\,{\rm T_v})</math> are to be real distances moved in a real time interval. It is hard for me to conceive of even one photon observing another photon and somehow reporting an observed distance. I don't believe that Pythagoras who relied more on the geometrical axioms of Euclid ca. 300 BC than on Einstein publishing in 1905 would appreciate or endorse being cited here. I see no other good source for the latter "pseudo-Pythagorean" equation and I conclude that it is introduced here as algebraic sleght-of-hand. The trick is to quote a supposed definition
<math>\gamma=\frac{\rm T_s}{\rm T_v}</math>
into which the trickster plugs <math>\rm T_s</math> and
<math>\rm T_v</math> that have been synthesized to give the standard result.
'''To point 1:''' The ploy is clever but hardly legitimate. [[Special:Contributions/2A02:FE1:4088:5E00:DC53:CFFC:3F4A:F5BE|2A02:FE1:4088:5E00:DC53:CFFC:3F4A:F5BE]] ([[User talk:2A02:FE1:4088:5E00:DC53:CFFC:3F4A:F5BE|talk]]) 15:33, 28 August 2025 (UTC)
:This is not a "Pseudo-Pythagorean" equation.
I asked some friends about this and we came to the educated guess that it had something to do with your muscles/other tissues wanting more oxygen, so they output some chemical that sends a signal to your brain to stretch, making more blood flow to your muscles....
:Perhaps [https://www.youtube.com/watch?v=qXxtqK7G4Uw&t=160s '''this derivation here'''] will be even clearer.
:I do apologise for not being able to show a geometric sketch in advance. [[User:יהודה שמחה ולדמן|יהודה שמחה ולדמן]] ([[User talk:יהודה שמחה ולדמן|talk]]) 18:27, 28 August 2025 (UTC)
::Isn't this the same derivation as given in {{section link|Time dilation#Simple inference}}?
::The presentation in the YouTube video is (IMO) in one respect somewhat confusing. There are two observers, one inside a moving train car, one standing outside next to the railroad tracks in the grass. There are two time values for the different times clocked by these observers, <math>T_{stationary}</math> and <math>T_{moving}.</math> Now in the narrative of the video <math>T_{stationary}</math> stands for the time clocked by the observer in the ''moving'' car, while <math>T_{moving}</math> is the time clocked by the observer patiently ''standing'' outside till this ordeal is over. I beg your pardon. (To be fair, the narrative gives a reasonable explanation for this choice, but note that the notation in the question has this swapped: <math>{\rm T_s}=T_{moving}</math> and <math>{\rm T_v}=T_{stationary}.</math>)
::The simple derivation given is based on vector decomposition of a velocity into a component in a given direction (in this case that of the velocity of the moving car) and an orthogonal component, and that this remains valid for a moving system observed from the outside. I don't know if this can be called an assumption – if so, it is hardly hidden — but the validity of this step may not be that obvious to the confused student all of whose implicit assumptions based on the Newtonian model of absolute time and space have lost their certainty and who may wonder what happened to length contraction.
::The presenter himself states that this is not his favourite derivation, and that there is a better, but more difficult explanation. ​‑‑[[User talk:Lambiam#top|Lambiam]] 08:47, 31 August 2025 (UTC)
= September 1 =
Is this even remotely accurate? what are the processes involved and why does your body force you to stretch?
== Getting rid of ants ==
[[Special:Contributions/137.81.116.186|137.81.116.186]] 14:29, 8 February 2011 (UTC) <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/137.81.116.186|137.81.116.186]] ([[User talk:137.81.116.186|talk]]) </span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
I am looking for a natural remedy to stop ants from entering my home. Is there any solution that I can make or create to get rid of them? [[User:Caralynn8|Caralynn8]] ([[User talk:Caralynn8|talk]]) 20:28, 1 September 2025 (UTC)
:I can't comment at the molecular level, but think the reason for it is to prevent muscle injuries. Just like you should stretch before running, you should also do that before using muscles for the first time each day. One thought is that it may be simply to increase the temperature, as muscles, tendons, etc., become more flexible and less likely to tear at higher temps. Locations far from the body core, like say the [[Achilles tendon]], are perhaps most likely to be cold in the morning (especially if your feet stick out from under the blankets), and thus in most need of a few warm-up exercises. [[User:StuRat|StuRat]] 16:58, 8 February 2011 (UTC)
:Maybe invest in an [[anteater]]? ←[[User:Baseball Bugs|Baseball Bugs]] <sup>''[[User talk:Baseball Bugs|What's up, Doc?]]''</sup> [[Special:Contributions/Baseball_Bugs|carrots]]→ 20:56, 1 September 2025 (UTC)
:[[Old Farmer's Almanac]]'s website addresses this [https://www.almanac.com/pest/ants here]. [[User:Modocc|Modocc]] ([[User talk:Modocc|talk]]) 21:09, 1 September 2025 (UTC)
== efficiency of household freezer ==
::As discussed in [[Stretching#Research and controversy]], the research is unclear about whether a few minutes of [[static stretching]] (the typical kind) ''before'' activities like running actually does prevent any injuries, and pre-event stretching may even have a negative impact on performance. Stretching matters more in sports where you need a very large range of motion, but running isn't one of those. Others suggest that [[dynamic stretching]] may have more of a benefit, but there isn't much research on that either way. It is however good to stretch or participate in other cool-down activities ''after'' exercise (including running), because it helps the muscles relax gradually and that is clearly found to help prevent injury. What any of this means for the early morning stretch, I don't really know. [[User:Dragons flight|Dragons flight]] ([[User talk:Dragons flight|talk]]) 21:00, 8 February 2011 (UTC)
:::There is a stretching "controversy", lol. I don't know why but I find that really funny.. Forgive me I haven't had my coffee yet. [[User:Vespine|Vespine]] ([[User talk:Vespine|talk]]) 21:37, 8 February 2011 (UTC)
I'm wondering how much electric energy it takes to freeze 1kg of water in a household fridge/freezer. So this iis a question about freezers rather chemistry (I know about heat of crystallization of water but the freezer itself also matters). A quick web search didn't find anything immediately useful, though maybe the SEER of air conditioners is sort of applicable. Ambient temperature is 77F and let's say the initial water temperature is similar. Any idea where to find this? Thanks. [[Special:Contributions/2601:644:8581:75B0:9592:EB5:353B:E636|2601:644:8581:75B0:9592:EB5:353B:E636]] ([[User talk:2601:644:8581:75B0:9592:EB5:353B:E636|talk]]) 23:03, 1 September 2025 (UTC)
:It's a combination of two things, first the fact that joints and muscles tend to stiffen when they are not in use due to the formation of adhesions between muscle fibers, second the properties of [[circadian rhythms]]. During the nighttime hours, body temperature drops and a variety of injury-repair mechanisms are activated -- both of these tend to promote formation of muscle and joint adhesions that are broken by stretching. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 22:54, 8 February 2011 (UTC)
= September 2 =
== A rifle with a barrel made of heat resistant ceramic ==
== Exact decimal Lorentz factor and speed ==
Is it possible to make something like this? [[User:ScienceApe|ScienceApe]] ([[User talk:ScienceApe|talk]]) 15:01, 8 February 2011 (UTC)
[[File:lorentz_factor_pythagorean_theorem.svg|thumb|upright|Lorentz factor depicted as a right triangle in a quadrant of radius 1.<ref>Wyrd Smythe, [http://logosconcarne.com/2020/12/09/sr-x6-moving-at-light-speed ''SR #X6: Moving at Light Speed''], Logos con carne, December 9, 2020</ref>]]
:Yes. It is possible. However, it is not as good as a regular barrel. Instead, it is common to have a regular barrel with a ceramic lining or coating. -- [[User:Kainaw|<font color='#ff0000'>k</font><font color='#cc0033'>a</font><font color='#990066'>i</font><font color='#660099'>n</font><font color='#3300cc'>a</font><font color='#0000ff'>w</font>]][[User talk:Kainaw|™]] 15:04, 8 February 2011 (UTC)
As a follow-up to the question above, are the speed of 0 giving the Lorentz factor of 1, and the speed of 0.6''c'' giving the Lorentz factor of 1.25 the only possible values with exact decimal representations (shown in bold on [[Lorentz_factor#Numerical_values]])?
I can see that it is related to [[Pythagorean triple]]s, and while 5, 25 and 125 are possible lengths of the hypoteneuse, the side of 4 is the only one of form 2<sup>x</sup>5<sup>y</sup>.
::Ceramics are generally too brittle to absorb shock loads without damage. The elasticity of the types of steel used for rifle barrels is what allows them to contain the shock (abrupt change in pressure) of firing. I would like to see some evidence of [[User:Kainaw]]'s claim that ceramic coatings or linings are common. I've seen and handled many different rifles in my life and I have yet to lay eyes on one with such a lining or coating. The overwhelming majority of rifle barrels are just steel with various finishes ranging from [[Bluing (steel)|blueing]], [[Parkerizing]], [[nitriding]], [[case hardening]] to plain and simple [[enamel paint]]. [[User:Dodger67|Roger]] ([[User talk:Dodger67|talk]]) 16:15, 8 February 2011 (UTC)
Thanks, '''[[User:cmglee|cmɢʟee]]''' [[User_Talk:cmglee|τaʟκ]] <span style="font-size:80%;">(please add <code>{{ping|cmglee}}</code> to your reply)</span> 02:35, 2 September 2025 (UTC)
:::Something I know next to nothing about but I wonder about that too from my searches. These 2 refs from 2003-2004 suggest it's an area of active research for the US army but not currently very successful [http://myweb.clemson.edu/~gmica/Publications/Ref_99.pdf] [http://ammtiac.alionscience.com/pdf/AMPQ8_4ART08.pdf]. Things may have changed a lot since then but if not I wonder how common it can be if even the army isn't doing it. It seems some companies to offer to coat existing guns, e.g. [https://forums.cabelas.com/showthread.php?t=13049] [http://www.handloadersbench.com/view_topic.php?id=10411&forum_id=5&jump_to=84959] but this doesn't sound like something which would be common. Incidentally from some of those refs I think chrome line barrels may be somewhat common. [[User:Nil Einne|Nil Einne]] ([[User talk:Nil Einne|talk]]) 16:23, 8 February 2011 (UTC)
:::(ECx3)Ceramics can be resistant to high temperature, and can have great compression strength. Do ceramics have the tensile strength to prevent the barrel splitting open from the outward directed pressure, without having a ridiculous wall thickness making the weapon non-portable? Aren't they generally brittle? [[User:Edison|Edison]] ([[User talk:Edison|talk]]) 16:25, 8 February 2011 (UTC)
::::As a general rule, ceramics are not good at tensile strength. Some composite materials like carbon fiber might be able to give greater tensile strength then ceramics, but they might still be brittle enough to shatter in that application.
== Hot body in vacuum ==
Suppose a solid sphere of metal of 1 sq.m (choose a convenient substance) of 100 deg.C perfectly isolated by any incoming energy in perfect vacuum. How much time it will take to get to the lowest temperature it can reach? --[[User:M121121121|M121121121]] ([[User talk:M121121121|talk]]) 20:53, 8 February 2011 (UTC)
:This sounds suspiciously like a homework question. No one here at Wikipedia is going to answer the question for you, but if you want some background on the concepts you need to solve it, see [[black body]] and [[thermal radiation]]. --[[User:Jayron32|<font style="color:#000099">Jayron</font>]]'''''[[User talk:Jayron32|<font style="color:#009900">32</font>]]''''' 21:03, 8 February 2011 (UTC)
:Forever. Assuming it were perfectly isolated (which is impossible, but we can assume it anyway), it would radiate energy away in ever decreasing amounts as it's temperature decays towards but never actually reaches 0 K. For details, see [[Stefan-Boltzmann equation]]. [[User:Dragons flight|Dragons flight]] ([[User talk:Dragons flight|talk]]) 21:06, 8 February 2011 (UTC)
It's not homework, but you're right. Who/where should I ask for this calculus? Please advice. --[[User:M121121121|M121121121]] ([[User talk:M121121121|talk]]) 21:24, 8 February 2011 (UTC)
::The appropriate equation to apply is the [[Stefan–Boltzmann law]], which defines the rate of heat loss from a body. It's worth noting that if the object is in the "empty vacuum of space", the relevant "cold sink" is the [[cosmic microwave background]], at around 3 kelvins. [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 21:30, 8 February 2011 (UTC)
:You said it is "perfectly isolated by any incoming energy":
:A) Assuming "by" means "from", that would mean it would also be perfectly isolated as far as radiating out energy. If there was such a perfect thermos, it would stay the initial temperature forever.
:B) If, however, we assume that it's the only source of energy in the universe, then it would radiate energy but not receive any back. In that case the temperature would decrease at a decreasing rate, but would still never quite reach absolute zero.
:C) If we assume it's in the real universe, but far from any source of energy, as in a galactic void, then the temperature would again decline at a decreasing rate, gradually approaching the average temperature in that void. [[User:StuRat|StuRat]] ([[User talk:StuRat|talk]]) 22:50, 8 February 2011 (UTC)
::Far out, when you were at school did you try to lecture your teacher about how there's no such thing as a perfectly frictionless surface? Don't take it personally but I completely don't see the problem with the way the question was asked. For the majority of hypothetical physics questions I've ever seen you are expected to leave the assumptions at the door. If it doesn't mention air resistance, ignore it, if it doesn't mention MBR: ignore it. If it says "perfect vacuum" don't think it actually means "real vacuum of space'… Given this premise, what is the result? Full stop. As far as I can tell, Dragon flight and StuRat answer B give the answer forever, which I think is correct, but if you had the "method" which I admit I don't, you could at least come up with some more meaningful replies, like maybe how long would it take to get to 50%, 1% and 0.1% of the absolute temperature. . [[User:Vespine|Vespine]] ([[User talk:Vespine|talk]])
:::<small>I have no problem with questions which have assumptions that don't exist in the real world, but we do need to be very specific about what those assumptions are, as they can change the answer dramatically. [[User:StuRat|StuRat]] ([[User talk:StuRat|talk]]) 06:18, 10 February 2011 (UTC)</small>
Reformulating the initial question: how much time needs an isolated object to loose all (as much as possible) its energy only by radiation? A naked human in outer space will freeze? (leave the zero pressure problem at this time)[[User:M121121121|M121121121]] ([[User talk:M121121121|talk]]) 07:39, 9 February 2011 (UTC)
:The colder it gets the slower it radiates (temperature to the power 4), so there is no answer to your first question. To your second question, if the human is in sunlight they won't freeze (but will get a horrible sunburn). If in the shade they will freeze eventually, see [[Stefan–Boltzmann law]] for the numbers. [[User:Ariel.|Ariel.]] ([[User talk:Ariel.|talk]]) 08:41, 9 February 2011 (UTC)
:Assuming that the sphere is hollow, painted black (special black to be a [[black body]]), and has a high conductivity, then the temperature will fall very quickly to a few (tens of) degrees Kelvin (because rate of fall in temperature is roughly proportional to the fourth power of absolute temperature if background microwave absorption is ignored). (The human body would lose heat much more slowly because of low conductivity.) I'm struggling with the constants to be able to find the solution to the differential equation. Perhaps someone more knowledgeable could make an estimate for a typical sphere. [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 08:44, 9 February 2011 (UTC)
== Homemade cavendish experiment . ==
I do enjoy this facinating webpage. I like seeing the videos of the "mass attracting mass" but I am still a little skeptical.
http://www.fourmilab.ch/gravitation/foobar/
It still seems a little strange to me to actually see gravity interacting with such homemade apparatus. Are the masses too small? Is there some kind of experimental error going on? Perhaps an electric force is causing this?
What do you think? <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/92.17.89.69|92.17.89.69]] ([[User talk:92.17.89.69|talk]]) 21:09, 8 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:Well, the [[Cavendish experiment]] is well known; and you can, using simple Newtonian physics equations, estimate what the force ''should'' be and decide if the magnitude of errors introduced by, say, turbulent air currents or electric forces are relevant. You can also eliminate (or at least, reduce) electrostatic effects by grounding all involved objects with electrically conductive wire. I have to say, the experiment seems pretty fantastic! But, as a firm believer in Gravity, I am at a loss to come up with a ''more'' plausible reason why the balance would torque in this way. (Though I admit, gravity is a bit implausible, but I observe it daily nonetheless). [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 21:39, 8 February 2011 (UTC)
:: Do objects tend to drift like this on say the ISS? Say they left a bowling ball hovering, would it accelerate towards the center of gravity on the space station? <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/92.17.89.69|92.17.89.69]] ([[User talk:92.17.89.69|talk]]) 21:59, 8 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
::::Assume a spherical hollow metal spaceship in orbit and a bowling ball released at a random spot inside, with no air currents. If I remember my physics course correctly, unless the spaceship accelerates, there is no reason for the bowling ball to move from its random release point, since the gravitation attraction of the spacecraft for its contents is effectively zero. The attraction from one part of the craft is cancelled by the attraction of the rest of the craft.
:::Center of Gravity? An object floating free in a orbiting vessel would be affected by the sum of the masses around it, relative speed and the air currents of the air conditioning system. Also, it may be deflected on route, by any skittles it meets on the way. The article on [[Micro-g environment]] may be of interest too.--[[User:Aspro|Aspro]] ([[User talk:Aspro|talk]]) 22:15, 8 February 2011 (UTC)
:::(ec) The ISS, and other manned spacecraft, are in "[[microgravity]]" - which is to say, not quite freefall. There's a small but measurable net force on the spacecraft at almost all times, caused by the acceleration due to non-ideal effects like [[gas drag]] and orbit correction maneuvering ([[stationkeeping]]). Stanford's [[Gravity Probe B]] might be interesting, though - an entire spacecraft was launched ''just to measure the gravitational nonlinearity'' under ideal conditions. Preliminary results were announced a couple of years ago (see this [http://einstein.stanford.edu/content/press_releases/SU/pr-aps-041807.pdf press release from April 2007's APS Plenary]; unfortunately, [http://www.newscientist.com/article/dn13938?feedId=online-news_rss20 the mission wasn't well-received] when the data turned out to be noisier than expected. [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 22:18, 8 February 2011 (UTC)
::::Speaking of spacecraft that are solely to measure gravity, check out the [[Gravity Recovery and Climate Experiment]]. Here, two spacecraft make fine measurements of the Earth's (slightly non-uniform) gravitational field. It's pretty amazing being able to watch the mass of the amazon change depending on which season it is. [[User:Buddy431|Buddy431]] ([[User talk:Buddy431|talk]]) 02:33, 9 February 2011 (UTC)
:The experimenter apparently did nothing to rule out electrostatic attraction as an explanation for the effects. The plastic foam arm is an excellent insulator, as is the monofilament line, and it would be amazing if there were no electric charge on the arm or the weights. A metal support wire, a wooden arm, and a wooden frame holding the other weights and all connected together like the Cavendish apparatus would be an improvement, since wood is a poor insulator in static electric terms. I have seen demos of charging a piece of PVC pipe by friction from a piece of fur, then using it to make a can of pop roll rapidly toward it, a stronger force by orders of magnitude than the gravitational attraction of the small weights. [[User:Edison|Edison]] ([[User talk:Edison|talk]]) 00:04, 10 February 2011 (UTC)
== The straw that stirs the drink ==
Whenever I pour a [[carbonated beverage]] into a glass and stick a straw in it, CO2 bubbles invariably attach to the straw, then lift it to the point where it seems like the straw should fall out of the glass. However, I have never had a straw actually fall out. What provides the force keeping the straw in place? Is there a length beyond which the straw will tumble? [[User:Agastordoff|Hemoroid Agastordoff]] ([[User talk:Agastordoff|talk]]) 22:03, 8 February 2011 (UTC)
:I have often had a straw fall out. Perhaps I fill my glass fuller? [[Special:Contributions/86.162.68.36|86.162.68.36]] ([[User talk:86.162.68.36|talk]]) 22:17, 8 February 2011 (UTC)
::Surface tension will sometimes prevent the straw from falling out, even when the centre of mass is outside the rim of the glass, but it will often be insufficient to prevent a long straw from falling out of a full glass. [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 08:12, 9 February 2011 (UTC)
== clouds ==
why are clouds white? [[Special:Contributions/71.2.42.116|71.2.42.116]] ([[User talk:71.2.42.116|talk]]) 22:11, 8 February 2011 (UTC)
:Have you discovered our search box? It just so happens, we have a article section on [[Clouds#Colouration|the colour of clouds]].--[[User:Aspro|Aspro]] ([[User talk:Aspro|talk]]) 22:23, 8 February 2011 (UTC)
== Sanitary drain(industrial sewer) sizing and design discharge flow rate estimate ==
how do I estimate discharge flow rate (L/s) based on the number of fixture units?--[[Special:Contributions/165.228.109.94|165.228.109.94]] ([[User talk:165.228.109.94|talk]]) 22:21, 8 February 2011 (UTC)
== Kilos instead of larger units ==
Why planet and star masses are commonly indicated in kilograms instead of more handy larger units, such as [[gigatonnes]] or [[teratonnes]] (where no [[exponentiation]] would be necessary)? <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/89.76.224.253|89.76.224.253]] ([[User talk:89.76.224.253|talk]]) 22:28, 8 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:Actually, most astrophysicists use [[cgs units]] - that is, ''grams'', to measure the mass of planets. Why? Because they're dealing with many orders of magnitude during different calculations, so they must use [[scientific notation]] anyway. In other words, exponentiation will be required, no matter what, so we might as well use it consistently. (Though, [http://www.amazon.com/Introduction-Electrodynamics-3rd-David-Griffiths/dp/013805326X Griffiths] and [http://casa.colorado.edu/~wcash/APS3730/chapter2.pdf others] attribute the ''cgs'' preference to electrodynamics, where the [[gauss (unit)|gauss]] and the convention of unitary [[permittivity of free space|permittivity-]] and [[magnetic permeability|permeability-]] of free space, require "less writing." Other physicists, cosmologists in particular, prefer [[dimensionless physical constant]]s, so they prefer the ("horribly inconvenient") SI units normalized by the values fundamental constants, called "[[planck units]]." As physicists, when we study planets and space science, we try to isolate any "biases" we might have in our system of units that are historical artifacts of measuring the size of the Earth. SI and cgs is not ''entirely'' guilt-free in that respect, as the meter is historically defined as a ratio to the earth's circumference. But in any case, if you're going to measure a planet's mass, it's still going to be "huge", whether you measure it in grams, tons, or [[solar mass|solar mass units]]; and if you measure two planets, chances are you'll need [[scientific notation]] in ''any'' unit system. [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 22:45, 8 February 2011 (UTC)
::Careful there Nimur. If one uses solar masses than the mass of a planet will not be a huge number and in fact that is the most common choice among astrophysicists (That is the choice of most of my books). Also, the Planck units are not horribly inconvenient. If they were, nobody would use them. Finally, the Plank system of units is not based on the SI as you stated. [[User:Dauto|Dauto]] ([[User talk:Dauto|talk]]) 02:47, 9 February 2011 (UTC)
:::I think you misread Nimur's phrasing. To be fair to you, it was not as hard to misread as it could have been. The "horribly inconvenient" refers, I think, to SI rather than to Planck units, and I don't see anything that suggests Nimur claimed the latter were based on the former. --[[User:Trovatore|Trovatore]] ([[User talk:Trovatore|talk]]) 03:18, 9 February 2011 (UTC)
::::"Horribly inconvenient" was meant to be tongue-in-cheek; obviously, any reasonable unit system has a purpose. And regarding "huge": I consider 1x10<sup>-6</sup> solar masses to be "huge", even if the number is represented as a minuscule fraction; my point was to illustrate that representational units don't actually change the size of the object. [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 07:56, 9 February 2011 (UTC)
== Help understanding Parsec illustration ==
Can someone chime in at [[Talk:Parsec#Dots in image]]? I didn't understand the image used in the article and would appreciate some help in that regard. Thanks, [[User:Waldir|Waldir]] <sup>[[User talk:Waldir|talk]]</sup> 22:54, 8 February 2011 (UTC)
:I think has been resolved. --[[User:Mr.98|Mr.98]] ([[User talk:Mr.98|talk]]) 13:50, 9 February 2011 (UTC)
== Trampolining gives you muscles? ==
An acquantance of mine has an amazing body. He has big legs, a six pack, good arms, and generally good upper body and back. When I asked him how many times a week he worked out he replied that hedidn't work out at all. He said he uses his mini trampoline every day. Can this be true? Google shows many health benefits of trampolining but it doesnt go into detail about muscle growth. I can understand how it might get you big legs but a six pack!?! Surely that would be reason enough for every guy anywhere to get one? Surely such a thing would widely known and not such a well kept secret? And asked him another day whether he really meant a mini trampoline and he replied affirmatively. I mean you cant ever do sommersaults on those! So how do you explain the good arms and upper body?
Edit: oh and by 'big' I may be exaggerating slightly. He doesnt loook like a body builder but he does have a very impressive slim athletic physique. <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/91.49.33.244|91.49.33.244]] ([[User talk:91.49.33.244|talk]]) 23:32, 8 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:What he didn't tell you is about all the steroids he takes. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 01:32, 9 February 2011 (UTC)
::I think as much as a lot of people argue to the contrary, not everyone is created equal. Genetics plays a not insignificant part in how your body will look as well as a countless number of other factors which might not even be considered "exercise". Things like diet and eating habits, sleep habits, lifestyle in general, things like how much you walk and even seemingly inconsequential things like do you "fidget", all these play a part in your physique. One very interesting comparison you can easily make is look at the competitors of fighting sports like [[UFC]], they are all without a doubt extremely fit individuals who train very hard but they still have widely varying body types. No doubt some of the extremes are due to drugs like the above suggests, but I believe even if you excluded that, you would still see a big difference between body shapes, like shoulder width, muscle definition even amongst people who have similar exercise routines.. There was a time before my brother and I had ever gone to the gym but he's always been much bigger then me, we grew up eating the same foods and doing similar activities, even though he was only 18 months older then me, in our teens I weiged between 60 and 70 and he weighed between 80 and 90 and wasn't slim but not exactly what you'd call "fat". [[User:Vespine|Vespine]] ([[User talk:Vespine|talk]]) 02:49, 9 February 2011 (UTC)
= February 9 =
== What's a good nonpolar organic solvent? ==
Preferably not carcinogenic. --[[Special:Contributions/75.15.161.185|75.15.161.185]] ([[User talk:75.15.161.185|talk]]) 00:26, 9 February 2011 (UTC)
:Can you be a bit more specific about your needs? How about [[cyclohexane]]? [[User:TenOfAllTrades|TenOfAllTrades]]([[User_talk:TenOfAllTrades|talk]]) 00:53, 9 February 2011 (UTC)
::It should be able to dissolve lipids but not other compounds in food. --[[Special:Contributions/75.15.161.185|75.15.161.185]] ([[User talk:75.15.161.185|talk]]) 02:32, 9 February 2011 (UTC)
:::Lipids are basically the entire class of all [[hydrophobic]] biological compounds, so by definition if it dissolves substantially in cyclohexane, it is a lipid. I am pretty sure that's how lipids were classified in the earliest days when such things were classified. See [[Lipid]] for more. --[[User:Jayron32|<font style="color:#000099">Jayron</font>]]'''''[[User talk:Jayron32|<font style="color:#009900">32</font>]]''''' 03:57, 9 February 2011 (UTC)
:::[[Vegetable_oil#Extraction]] notes that [[hexane]] and [[supercritical carbon dioxide]] are used commercially to extract oils from the vegetable matter. (I assume that there's probably a food-grade hexane for that purpose.)-- [[Special:Contributions/174.24.195.38|174.24.195.38]] ([[User talk:174.24.195.38|talk]]) 04:10, 9 February 2011 (UTC)
== Flight control surfaces on modern airliners ==
In modern airliners, how do the flight control surfaces work? I know that they are usually powered by hydraulics, but how is the power applied from the hydraulic system to the control surfaces? Is it a cable system, levers and hydraulic cylinders, etc.? Also, what does the mechanism inside the flap canoes/fairings look like and how do they work?[[Special:Contributions/67.169.5.125|67.169.5.125]] ([[User talk:67.169.5.125|talk]]) 05:25, 9 February 2011 (UTC)
:The engines drive hydraulic pumps through their accessory gearboxes. The control inputs by the pilots are interpreted by the flight control computers which in turn actuate various valves to move the relevant hydraulic rams attached to the control surfaces. Feedback from the surfaces is returned to the flight control computers which in turn move the controls to provide tactile feedback to the pilots. This is the short answer - for a more comprehensive answer, read [[Fly-by-wire]]. [[User:Dodger67|Roger]] ([[User talk:Dodger67|talk]]) 08:44, 9 February 2011 (UTC)
== Homework question on momentum + pendulum ==
Hi all,
I have a physics homework that I am completely stuck on. I have no clue how to approach this question at all. Any help would be appreciated!
In a ballistic pendulum an object of mass m is fired with an initial speed v_0 at a pendulum bob. The bob has a mass M, which is suspended by a rod of length L and negligible mass. After the collision, the pendulum and object stick together and swing to a maximum angular displacement theta as shown .
http://session.masteringphysics.com/problemAsset/1010989/28/1010989A.jpg
Find an expression for v_0, the initial speed of the fired object.
Again, any help would be appreciated!! <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/169.232.78.43|169.232.78.43]] ([[User talk:169.232.78.43|talk]]) 05:45, 9 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:The calculations actually have two parts. When the bullet impacts the bob, kinetic energy is lost to friction, but momentum is concerved. When angle theta is reached and the bob is at rest, the remaining kinetic energy (which you can calculate from knowing what the momentum will be) has become gravitational potential energy. If you can write out the formulae for all of that, you can solve for V<sub>o</sub> in terms of theta, L, m and M. [[User:Someguy1221|Someguy1221]] ([[User talk:Someguy1221|talk]]) 05:56, 9 February 2011 (UTC)
::Initially, I would tackle this problem using the principle of conservation of linear momentum. Momentum of object prior to impact equals momentum of object plus bob after impact.
::[[Mechanical energy]] is not conserved during the collision because some of the initial energy of the object is converted to heat, and some is used in deformation of itself and the bob as it enters. Kinetic energy and potential energy can be calculated for the period after the collision. [[Mechanical energy]] is then conserved for the period from the end of the collision until the bob comes to rest, and that should yield your answer. [[User:Dolphin51|<font color="green">''Dolphin''</font>]] ''([[User talk:Dolphin51|<font color="blue">t</font>]])'' 07:16, 10 February 2011 (UTC)
== are ==
are concrete warehouses like bestbuy insulated i see none <small><span class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Tomjohnson357|Tomjohnson357]] ([[User talk:Tomjohnson357|talk]] • [[Special:Contributions/Tomjohnson357|contribs]]) 06:44, 9 February 2011 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->
:[[Punctuation]] would help us to understand your question. --[[User:Lgriot|Lgriot]] ([[User talk:Lgriot|talk]]) 08:34, 9 February 2011 (UTC)
:There's lots of ways they could do it. Probably the simplest is a double wall with insulation in between like this: [[Insulated concrete form]]. Or you install metal studs inside the building and insulation between them, then drywall. [[User:Ariel.|Ariel.]] ([[User talk:Ariel.|talk]]) 08:46, 9 February 2011 (UTC)
== If the universe is not spherical... ==
When something expands at the same rate from a single point, the result is a sphere. If something expands at different rates in different places, the final result is a non-spherical shape.
So, if the universe is flat, saddle-shaped or anything but a sphere, what mechanism explains this uneven distribution of expansion? Thanks. [[User:Leptictidium|Leptictidium]] (''[[User talk:Leptictidium|mt]]'') 07:35, 9 February 2011 (UTC)
:If I'm reading you right, your question assumes that the universe expanded from a point into the nothingness around it. That's not the case. The universe would have always had its current overall topology, and has simply been getting bigger. [[User:Someguy1221|Someguy1221]] ([[User talk:Someguy1221|talk]]) 08:29, 9 February 2011 (UTC)
::So, assuming the universe is flat: the Universe wouldn't have expanded from a single point, as proposed by the Big Bang theory, but rather from a single, infinitely small, "sheet of paper"? [[User:Leptictidium|Leptictidium]] (''[[User talk:Leptictidium|mt]]'') 09:18, 9 February 2011 (UTC)
:::No, but I'm going to wait for someone with a better grasp of generaly relativity to really answer that, but in the meantime please treat yourself to [[metric expansion of space]]. [[User:Someguy1221|Someguy1221]] ([[User talk:Someguy1221|talk]]) 09:25, 9 February 2011 (UTC)
:If you insist on imagining that the universe expanded from a single point then you have to remember that this point is not embedded in some empty space. The point ''is'' the entire space, it is not embedded in anything. However, it is better to remember that the "Big Bang" is actually nothing but the result of an extrapolation of the observed expansion ''backwards'' in time, and in fact beyond the limits where our understanding of physics holds (which gets close to the BB but does not reach it). We do not know what the Big Bang looked like. --[[User:Wrongfilter|Wrongfilter]] ([[User talk:Wrongfilter|talk]]) 09:41, 9 February 2011 (UTC)
::Indeed. The [[Big Bang]] theory does ''not'' assume that the Universe "expanded from a single point". It proposes that the Universe was originally in a very hot, dense state; it makes no assumptions about the topology of spacetime in this state. Also, [[User:Leptictidium|Leptictidium]], I think you have misunderstood the meaning of "flat" when applied to a four-dimensional manifold such as spacetime. You may learn more by reading our articles on the [[shape of the Universe]] and the [[flatness problem]]. [[User:Gandalf61|Gandalf61]] ([[User talk:Gandalf61|talk]]) 09:57, 9 February 2011 (UTC)
== Why would faster than light travel mean going back in time? ==
It's a point that I don't really understand. Yeah, sure, perhaps nothing can go faster than light, but I don't get the "going back in time" bit. If when I look at the Moon, I see it as it was about 1.5 seconds ago, then if I flash myself there instanteously, I would be there as it is right now, 1.5 seconds into the future of what I was seeing. What is paradoxical about that? When I am far away from a man chopping wood, I hear the axe hit the wood well after I see it strike. If I move next to him, then I see and hear the chop at the same time. If everyone was blind, and had to depend to sound only, would someone argue that if sound could travel instantaneosly, you could go back into time?
Also, while it has been observed and now measured very thoroughly, we know that everyone sees light travelling at the same speed regardless of their own local motion, or that of the object which is transmitting the light. But I don't think it has ever been shown why this is true, or has to be true. Is that right?
[[User:Myles325a|Myles325a]] ([[User talk:Myles325a|talk]]) 11:07, 9 February 2011 (UTC)
:To answer your first question - strictly speaking, the [[special theory of relativity]] does not forbid an object from travelling faster than the speed of light - it forbids an object from accelerating from a slower-than-light speed to a faster-than-light speed (or vice versa). This is because an object with a non-zero [[rest mass]] would have an infinite [[relativistic mass]] and hence infinite energy if it ever travalled at the speed of light. [[Photon]]s side step this problem by having zero rest mass - but as a result they can only ever travel at the speed of light, and cannot speed up or slow down. Physicists have postulated hypothetical particles called [[tachyon]]s that always travel faster than the speed of light. Although tachyons do not violate special relativity, they have some strange properties such as "imaginary" mass, and they also appear to violate the principle of [[Causality (physics)|causality]], so most physicists do not believe they can exist in our universe. [[User:Gandalf61|Gandalf61]] ([[User talk:Gandalf61|talk]]) 11:46, 9 February 2011 (UTC)
::I've drawn some ASCII space-time diagrams in the early history of the internet, but can't seem to find them anymore. The problem is that if you go faster than the speed of light in one inertial system, you go back in time in another (relatively moving) inertial system. Take a look at [[Minkowski diagram]], and in particular at [[Minkowski diagram#Constancy_of_the_speed_of_light]] and the following two sections. --[[User:Stephan Schulz|Stephan Schulz]] ([[User talk:Stephan Schulz|talk]]) 12:28, 9 February 2011 (UTC)
See also this article: [[Tachyonic antitelephone]]. So, if you can violate the speed of light limit by merely being able to send information faster than light (regardless of how you do it), then you can exploit this to build a device that is able to send information back into your own past. You can then build a "telephone" with which you can talk to yourself in the past. This then leads to a causal paradox because if you receice a phonecall now from your future self living tomorrow, you can then decide not to call past self tomorrow while, if you don't receive a phonecall, you can decide to call yourself. So, a clear paradox is obtained. [[User:Count Iblis|Count Iblis]] ([[User talk:Count Iblis|talk]]) 13:50, 9 February 2011 (UTC)
:You say "you can decide", but this seems open to dispute. One assumes that a four-dimensional spacetime that in some region curves back on itself admits a mathematical solution, just as one which does not. [[User:Wnt|Wnt]] ([[User talk:Wnt|talk]]) 21:13, 9 February 2011 (UTC)
[[Image:World line.svg|250px|right|thumb|Light cone in 2D space plus a time dimension.]]
Let me explain using the light cone picture I've added. For any given point in space-time, the remainder of space-time can be divided into four zones called the ''absolute future'' (points that can be reached by traveling slower than light), the ''absolute past'' (points from which the current point can be reached by traveling slower than the speed of light), the ''absolute present'' (points lying directly on the light cone), and the ''absolute elsewhere'' (points lying outside both the future and past light cones). These zones are the same regardless of the velocity of the observer. If it is possible to send signals faster than the speed of light, then it is possible to send signals to points in the absolute elsewhere. In fact, by altering the velocity of the signal source, it is possible to send signals to ''any'' point in the absolute elsewhere. But if you pick a point in the absolute elsewhere and draws its light cone, you will see that the absolute elsewhere for that second point overlaps with the absolute past of the first point -- meaning that a return signal from the second point can end up in the past of the first point. The crucial point is that the only velocity-independent distinction between past and future is that given by the light cone. Within the absolute elsewhere, the distinction between past and future is a function of the velocity of the observer -- any particular point can lie either in the past or the future, depending on how the observer is moving. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 17:46, 9 February 2011 (UTC)
:This assumes that the person can travel infinitely fast ''in any frame''. However, it is possible that an ansible may allow infinitely fast transport in only one privileged frame at any given point in space, such as the frame of the cosmic microwave background or the aggregate mass of the universe. This frame presumably varies according to Hubble expansion, gravity and so on. In this way, an observer with some velocity relative to this absolute frame may see the ansible capable of transmitting into the past ''in one direction'', but only into the future at a finite faster than light velocity in the opposite direction. But he never sees anything capable of transmitting into ''its own past''. (this is akin to the [[one-way speed of light]] mind game) [[User:Wnt|Wnt]] ([[User talk:Wnt|talk]]) 22:22, 9 February 2011 (UTC)
== Orbits and angular momentum ==
I love science but i'm not a scientist, so apologies if some of the terminology in this question is incorrect. Why do the planets orbit the sun on a single plane? Similar examples are planetary discs, or the stars within a galaxy - they all orbit on a plane as opposed to on a shell (think of the simplistic model of an electron 'shell' orbiting a nucleus). Is it something to do with angular momentum? <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/80.168.88.74|80.168.88.74]] ([[User talk:80.168.88.74|talk]]) 12:17, 9 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:The article [[Formation and evolution of the Solar System]] and related [[Protoplanetary disk]] and [[nebular hypothesis]] explain quite a bit. In simplest terms (and I may get this a bit wrong, so actual physics people can correct me) is that as a cloud of debris rotates around a star, it forms a disk around the equator of the sun, the forces involved in the spinning encourge that shape. Since the planets all form out of the material of that disk, they retain that roughly planar orientation with each other. This is different from electrons "orbiting" a nucleus, because the electron cloud itself doesn't revolve around the nucleus. Also, so-called "spins" in electrons and in the nucleus of an atom is not actual physical "spinning", rather it is a property which obeys the mathematical rules of spinning; but it does not seem that electrons and nuclei actually rotate like a star or planet does. --[[User:Jayron32|<font style="color:#000099">Jayron</font>]]'''''[[User talk:Jayron32|<font style="color:#009900">32</font>]]''''' 13:06, 9 February 2011 (UTC)
:: Thank you Jayron. From the Formation article you linked to - "the competing forces of gravity, gas pressure, magnetic fields, and rotation caused the contracting nebula to flatten into a spinning protoplanetary disc". Could you explain how these forces cause the flattening? The spinning/flattening pizza dough in the article is a good analagy, it's just understanding how all these forces result in the net effect of flattening that I struggle to understand. <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/80.168.88.74|80.168.88.74]] ([[User talk:80.168.88.74|talk]]) 14:03, 9 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:::Very simple explanation: gravity wants <math>x=y=z=0</math>, but [[conservation of angular momentum]] prevents ''x'' and ''y'' from being 0 (except momentarily in the course of an orbit). Gravity gets its way in the third dimension, so the result is flat.
:::More detail: The angular momentum effect is quantified in the [[effective potential]] that prohibits having all the mass at the center (consider what happens in the last equation in that article when ''r'' is very small). Nothing prevents ''most'' of the mass from piling up at the center: that's the Sun. Moreover, the restriction only applies in [[ecliptic|the one plane perpendicular to the momentum]]; anything outside that plane returns to it at some point during its orbit, and it then has the opportunity to collide with other objects in the plane. Eventually almost all motion perpendicular to the plane is arrested and you get a disk. (I don't know the particular role that magnetism plays here.) --[[User:Tardis|Tardis]] ([[User talk:Tardis|talk]]) 16:45, 9 February 2011 (UTC)
::::The mathematics of the [[Principal_axis_(mechanics)#Principal_axes_of_inertia|principal axes]] might be useful here. Without diving ''too'' deeply in to complicated mechanics treatment, it is a fact of physics that angular momentum must be conserved; and it is also a fact that in a lossy system (e.g., an [[n-body problem|''n''-body system]] with non-negligible gravitation between particles, and with collisions), even if [[rotational kinetic energy]] is initially distributed uniformly in the macroscopic system, inter-particle interactions will "leak" energy into the principle axes of the system. (You can accept this on faith, or you can work out the long-term evolution of the statistics of the [[equipartition theorem]] for an n-body gravitational system with collisions). It's not all that different from these nifty toys: [[Rattleback|tops that "only spin in one direction"]]. The thing is, the system has conditions that allow energy to transfer from one mode of rotation (say, "aplanar" orbits with random alignments), towards a preferred, principle mode of rotation (planar orbits, aligned in the plane of the system's initial net angular momentum vector). [[Rattleback#Physics|Because of lossy system-instabilities]], rotational energy concentrates into one mode. [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 22:55, 9 February 2011 (UTC)
:[[Accretion disc]] is an interesting article about the subject. - [[User:Ranemanoj|manya]] ([[User talk:Ranemanoj|talk]]) 04:06, 10 February 2011 (UTC)
: Aha! I've just had a eureka moment! I've been reading the articles you've all kindly linked to and they all helped. My understanding is that gravity and angular momentum are the two main forces. Gravity reduces the z axis to 0, whilst angular momentum prevents the x and y axis from being 0, the shape of which is a flat disc. This looks similar to Tardis' description, but it's taken all your responses to get me there, so thanks. <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/80.168.88.74|80.168.88.74]] ([[User talk:80.168.88.74|talk]]) 10:44, 10 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
== Straight line contrails ==
Why is it that nearly all vapour trails from aircraft show as a straight line? I have seen them expand as they get further from the plane but I would expect them to curve as the effects of cross winds move the vapour accross the sky.[[Special:Contributions/82.69.87.152|82.69.87.152]] ([[User talk:82.69.87.152|talk]]) 12:56, 9 February 2011 (UTC)
: The contrails do move with the wind. But that's no reason for them to curve. If the wind and the plane's course are both steady, you get ''straight'' contrails that extend from the current position of the plane in a direction that differs slightly from the plane's (ground-based) course. –[[User:Henning Makholm|Henning Makholm]] ([[User talk:Henning Makholm|talk]]) 13:23, 9 February 2011 (UTC)
::[http://contrailscience.com/racetrack-contrails/ Here's an illustration] of Henning's point. The photo at the link shows the contrails left by an aircraft in a holding pattern, flying a 'racetrack' circuit over and over. While the plane always passes over the same track on the ground, the wind moves the contrails so that each loop of the pattern is offset slightly from the one before. [[User:TenOfAllTrades|TenOfAllTrades]]([[User_talk:TenOfAllTrades|talk]]) 14:19, 9 February 2011 (UTC)
== is it a scientific fact that there is never a miscommunication between the tides and the moon that causes them? ==
Is it a scientific fact that there is never a miscommunication between the tides and the moon that causes them? [[Special:Contributions/217.136.92.148|217.136.92.148]] ([[User talk:217.136.92.148|talk]]) 13:07, 9 February 2011 (UTC)
:First, you must define what you mean by "miscommunication". Otherwise, your question is nonsense. It is not possible to provide a reference for nonsense questions. Because this is not a chat room, we do not chat about nonsense. -- [[User:Kainaw|<font color='#ff0000'>k</font><font color='#cc0033'>a</font><font color='#990066'>i</font><font color='#660099'>n</font><font color='#3300cc'>a</font><font color='#0000ff'>w</font>]][[User talk:Kainaw|™]] 13:16, 9 February 2011 (UTC)
::The only possible way I can think of for the tides to not sync properly with the moon would be if there was a celestial body that had a gravitational influence on earth that was a significant percentage of the gravitational influence the moon had which was on the opposite side of the earth. In normal circumstances, the sun has the second greatest impact on the tides though it is too small to cancel out the lunar tidal impact in even the most extreme circumstances. This would mean that you would need something extremely large to pass by the earth at close range to cancel out the tidal force generated by the moon, and in that case, I would be far more worried about impacts to earth's orbit around the sun then a short term hiccough in the tidal cycle. [[User:Googlemeister|Googlemeister]] ([[User talk:Googlemeister|talk]]) 14:13, 9 February 2011 (UTC)
::I suggest you read our article on [[tide]]s and then come back here if there is something you don't understand.--[[User:Shantavira|Shantavira]]|[[User talk:Shantavira|<sup>feed me</sup>]] 14:08, 9 February 2011 (UTC)
:The original post is just trolling about the scientific illiteracy of [[Bill O'Reilly]]: [http://scienceinthesky.com/2011/01/08/the-science-illiteracy-of-bill-oreilly/]. [[User:TenOfAllTrades|TenOfAllTrades]]([[User_talk:TenOfAllTrades|talk]]) 14:12, 9 February 2011 (UTC)
You guys are not reading my question. I want to know if there's ever been a case of MISCOMMUNICATION - where the moon's gravity was not properly communicated, and the tides did not come in in response. I can put it to you this way: if gravitons are what transfer gravity, and gravitons are particles, has there ever been a case of a service interruption between the moon and Earth, so that these particles were dropped. Or, have they ALWAYS, come through, never a miscommunication? [[Special:Contributions/217.136.92.148|217.136.92.148]] ([[User talk:217.136.92.148|talk]]) 14:52, 9 February 2011 (UTC)
:Only if you didn't pay your bill for gravitation service. You ''did'' remember to pay, didn't you? '''<font face="Arial">[[User:Acroterion|<font color="black">Acroterion</font>]] <sub><small>[[User talk:Acroterion|<font color="gray">(talk)</font>]]</small></sub></font>''' 15:00, 9 February 2011 (UTC)
:: Ha,ha, very funny. I've only been around since 1985, whereas there have been references to the moon and tides since at least the nineteenth century. [[Special:Contributions/217.136.92.148|217.136.92.148]] ([[User talk:217.136.92.148|talk]]) 15:02, 9 February 2011 (UTC)
::: There have been references to tides for as long as people have lived next to the sea and written about it. In seriousness, tides ''can'' be interrupted locally or otherwise affected by abnormal meteorological conditions, or, as we saw a few years ago, by earthquakes, neither of which have anything to do with the earth vs. Moon. Note that the sun makes tides too, accounting for [[spring tide]] and [[neap tide]]. Interruptions in gravity would be apparent by astronomical observation; so far as anybody knows, gravity has worked continuously since shortly after the Big Bang. '''<font face="Arial">[[User:Acroterion|<font color="black">Acroterion</font>]] <sub><small>[[User talk:Acroterion|<font color="gray">(talk)</font>]]</small></sub></font>''' 15:10, 9 February 2011 (UTC)
:::: yeah I'm not asking about other disruptions in the tide, but about a miscommunication with the moon. I'm not interested in gravity everywhere, but the communication of gravity between the mean and the tides it causes. Scientifically, has there ever been a miscommunication? [[Special:Contributions/217.136.92.148|217.136.92.148]] ([[User talk:217.136.92.148|talk]]) 15:15, 9 February 2011 (UTC)
:::::No there has not; neither can I think of a mechanism which would cause any such "miscommunication". Can we close the matter now? --[[User:Tagishsimon|Tagishsimon]] [[User_talk:Tagishsimon|(talk)]] 15:18, 9 February 2011 (UTC)
:::::: You say "now" as though this answer has been given above: in fact, you are the first to reply to my question. (And then only at my repeated insistence). Now, this being the reference desk, would you have any way to tell me why you answer "no there has not"... How would we know if there had been a miscommunication at some point in the history of Earth and Moon? (If gravitons had been interrupted at some point, how would we know that.) Thanks. [[Special:Contributions/217.136.92.148|217.136.92.148]] ([[User talk:217.136.92.148|talk]]) 16:08, 9 February 2011 (UTC)
:::::::In fairness, I think most of the above posts were pointing in much the same direction. Still. I'm glad you accept that byou have an answer to your first question. As to your second question: I don't know. I tend to doubt there would be any forensic evidence we could latch onto. And I tend also to think that the firm expectation is that the laws of physics in this area are well enough proven that no-one is looking for the sort of "miscommunication" which I infer you to be asking about. You might want to read the [[Evidence of absence]] article to improve your grasp of this notion of "scientific fact". In my universe, there are hypotheses which have greater or lessor amounts of experimental or observational proof attached to them. These are what amount to "facts". And then there's a whole limitless cornucopia of stuff which is not proven or which cannot be proven, and which falls outside the "fact" category. Your "miscommunication" seems to fall into that bucket ... no one expects such miscommunication, no one is looking for it, there is no proof that it has not happened, but that says little or nothing about whether it has happened. Gravitational theory does not provide any mechanics for it happening. Astrophysics (admittedly to my very limited knowledge) has no examples of this sort of thing going on. On that basis, most of us are content to say "it's never happened & will not happen", but when coming up against a pedant, would add something like "to the limit of current scientific understanding". Does that help? --[[User:Tagishsimon|Tagishsimon]] [[User_talk:Tagishsimon|(talk)]] 16:31, 9 February 2011 (UTC)
: I think we can safely so that No, there has never been a case of the moon's gravity mysteriously not working. (If it ever did, I think tides would be the least of our worries, actually. It would presumably slip out of its orbit. If it ever happened to the earth-sun gravity we'd ''really'' be in trouble.) Tide tables can be calculated far in advance and on days with no wind they're usually spot on.
: If gravity is caused by [[graviton]] particles, I suppose it's possible that a few of them might decay or otherwise go astray during the earth-moon trip. Perhaps that's what you're asking? But since gravitons aren't known to exist, this kind of speculation is less "theoretical physics" and more "making wild guesses about physics". In any case, that sort of "miscommunication" would be so infinitesimally small as to be completely unmeasurable. [[User:APL|APL]] ([[User talk:APL|talk]]) 15:23, 9 February 2011 (UTC)
I think the original question is probably based on some kind of bizarre misunderstanding, but it may be worth pointing out that the relationship between tides and moon is pretty complicated. Tides in any given ___location are generated by a combination of driving by the sun and moon, and the [[tidal resonance]] properties of nearby bodies of water. What you get, generally, is a complex oscillation that combines waves with lunar frequency, waves with solar frequency, and waves with local resonance frequencies. Large tides, such as those in the [[Bay of Fundy]], occur when the resonance frequency is a close match to the lunar frequency. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 17:28, 9 February 2011 (UTC)
:I vote "troll", and that's pretty rare for me. [[User:Comet Tuttle|Comet Tuttle]] ([[User talk:Comet Tuttle|talk]]) 17:34, 9 February 2011 (UTC)
::As TenOfAllTrades already pointed out above, this is a rehash of Bill O'Reilly's brilliant proof of god (and I quote verbatim):"[Sun goes up, sun goes down,] tide comes in, tide goes out, never a miscommunication". What makes this ridiculous argument somewhat remarkable is that O'Reilly has been taped on numerous occasions saying those exact words, and given that "miscommunication" is not exactly an everyday word it makes him sound like he at first rehearsed the argument in front of a mirror or something until he had it down pat, ready to lash it out if the occasion demanded it. [[User:TomorrowTime|TomorrowTime]] ([[User talk:TomorrowTime|talk]]) 17:47, 9 February 2011 (UTC)
The possibility that there would be a "miscommunication" between the moon and the tides is exactly the same, scientifically, as the possibility that there could be a "miscommunication" between your body in the ground, so that you'd wake up hovering three feet above your bed. Scientists, understandably, will look at you slightly strange if you start seriously suggesting that in order to fly, all you have to do is forget to fall. They'll think you're "[[Looney Tunes]]". -- [[Special:Contributions/174.24.195.38|174.24.195.38]] ([[User talk:174.24.195.38|talk]]) 17:36, 9 February 2011 (UTC)
: Why, has ''that'' ever happened? If not, I don't really get why you're bringing it up... [[Special:Contributions/217.136.92.148|217.136.92.148]] ([[User talk:217.136.92.148|talk]]) 18:11, 9 February 2011 (UTC)
:: The fact that it has never happened is exactly why the editor brought it up. [[User:Ndteegarden|thx1138]] ([[User talk:Ndteegarden|talk]]) 19:50, 9 February 2011 (UTC)
:::It is a scientific fact that [[Newton's law of gravity]] (as adjusted by [[relativity]]) has never been reliably observed to fail either through lack of communication or for any other reason, either between a human body and the earth, or between the moon and the tides. We don't really get why you're bringing it up... [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 22:41, 9 February 2011 (UTC)
:::: I'm bringing it up to verify Bill O'Reilly's ''premise'' (not his conclusion) about "never a miscommunication". I don't now about his conclusion, but from everything you all have written above, his premise is completely true and valid. Tide goes in, tide goes out, never a miscommunication. [[Special:Contributions/109.128.101.244|109.128.101.244]] ([[User talk:109.128.101.244|talk]]) 11:42, 10 February 2011 (UTC)
:The art, or rather the knack, to flying is not forgetting to fall, but throwing oneself at the ground and missing. --[[User:Tango|Tango]] ([[User talk:Tango|talk]]) 23:34, 9 February 2011 (UTC)
::Correct Tango. I suppose missing would qualify as a miscommunication? [[User:Chipmunkdavis|Chipmunkdavis]] ([[User talk:Chipmunkdavis|talk]]) 12:06, 10 February 2011 (UTC)
:::So if your person attempting flight was to be entangled in barbed wire and not hit the ground, you could argue that he is indeed flying? Sounds more like hovering to me then actual flight. [[User:Googlemeister|Googlemeister]] ([[User talk:Googlemeister|talk]]) 14:20, 10 February 2011 (UTC)
== Is natural non-grey hair possible in old age? ==
Is it possible for this gentleman http://www.bbc.co.uk/news/world-europe-12404554 and other people of similar age to have naturally non-grey etc hair? Or must it be artificially dyed? I recall other politicians in continental europe also have youthful-looking hair. Now I think of it, bald politicians are very rare too. [[Special:Contributions/92.24.185.155|92.24.185.155]] ([[User talk:92.24.185.155|talk]]) 13:36, 9 February 2011 (UTC)
:Fading of hair colour and loss of hair have a largely genetic component. Some of it is associated with the original hair colour (so blond hair tends to go grey faster than black hair, for example). My own grandfather had a full head of raven hair well into his 60s, while some people go bald or grey in their 20s. [[Special:Contributions/86.164.25.178|86.164.25.178]] ([[User talk:86.164.25.178|talk]]) 14:14, 9 February 2011 (UTC)
::I know a woman who had dark hair into her 90s; I've not seen her for a few years, but as far as I know, she might still have dark hair. [[User:Nyttend|Nyttend]] ([[User talk:Nyttend|talk]]) 23:31, 9 February 2011 (UTC)
== Quality of 2011 transistor radio v. 1940s top of the range valve radio? ==
Would the sound quality that I get from a modern cheap transistor radio be better than that of the most de-luxe valve radio of say the 1940s? Allowing for the fact that 1940's AM radio may not have been so crowded or subject to noise as it is now. Thanks. [[Special:Contributions/92.24.185.155|92.24.185.155]] ([[User talk:92.24.185.155|talk]]) 14:11, 9 February 2011 (UTC)
:For the sake of this hypothetical scenario, are both radios tuning in to the same radio transmission, or should we assume that you want to compare the quality of a 1940s broadcast to a 2011-era broadcast? Modern transistor radios can tune to FM, they can use "digital AM", and so on; so it's unfair to compare different types of transmissions that a 1940 tube radio could not demodulate in the first place. In terms only of noise quality and frequency fidelity between dc and 22 kHz, the best quality 1940s valve radios probably had equal performance to mediocre low-quality AM/FM asic integrated circuit tuner/demodulator/amplifier packages. And to be fair, "[[transistor radio]]" is a loosely used term: it historically referred only to those radios that used a single BJT for mixing (demodulating); but may also refer to a transistor power-amplifier, or to a modern fully integrated analog/digital mixed-signal system-on-chip radio and audio-amplifier package. If you want to be very precise, you'll have to specify what ''exactly'' you want a comparison between. [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 21:28, 9 February 2011 (UTC)
::I don't know about technical sound quality, but I certainly prefer the sound output from a 1940s radio. I find cheap "trannies" annoyingly hissy and tinny, but this is probably a combination of poor reception, cross-channel interference and small loudspeakers. I've never heard a high quality transistor radio, but I expect it would sound better if I rigged up a large aerial to pick up a suitable signal. (Only long wave and satellite digital radio work properly where I live.) [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 22:32, 9 February 2011 (UTC)
:::Is that tinny-ness the effect of the radio or the speaker-cabinet? Cheap radios often do have poor low-frequency fidelity; often, a DC-blocking capacitor is added as a "high pass filter" to cut everything below, say, 200 Hz; but this is usually intentional because they are connected to miniature battery-powered speakers that couldn't reproduce those low frequency acoustics ''anyway''. So we've got to compare apples to apples: the actual electrical output from a transistor tuner/amplifier is ''probably'' a higher-fidelity signal reconstruction of the original waveform. Post-processing ([[signal conditioning]]) can then be applied to make the device more suitable for portable/battery-operated speakers, at the expense of tone quality. [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 22:36, 9 February 2011 (UTC)
::::Yes, I'm sure you are correct about the circuitry, but for reception and sound output, I vote for the 1940s. There was considerable sound distortion in the decoding and amplifier circuitry in valve radios, but it was a very different distortion, and not nearly so annoying (or is it just that I got accustomed to it?) [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 22:52, 9 February 2011 (UTC)
:::::Oh, it's a well-known fact among audiophiles that "exact, flawless, perfect recreation of input signal" is not pin-for-pin compatible with "pleasant-sounding." For example, an electric guitar effects-box ''intentionally adds noise'' to the signal (in various different ways, depending on the effect), because people like the way that distortion sounds. I happen to like the tone properties of valve amplifiers, myself; there are many aesthetic details of old technology that are very nice. And I still prefer the fades and fuzzes of AM radio, even though this "new-fangled" FM-technology can provide stereo sound. It's fun to hear WSM fuzz out when I'm driving past a mountain or a rainstorm, and there's no thrill like picking up the Nashville stations while I'm driving through West Texas. (Try doing ''that'' with an [[Radio Data System|RDS-enabled side-channel]] stereo FM! Kids today, with their "technology...") But I can't objectively call it "better sound quality." [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 23:10, 9 February 2011 (UTC)
:::::::I've owned and listened to radios made in the 1920's, 1930's and 1940's. Not all 1940 radios were alike. Some were cheaply made with low output power, only a few tubes and a small cabinet, with a poor quality speaker. Those would be comparable to a modern very cheap and very small radio, which has wonderful signal processing combined with a tiny speaker enclosure which limits bass response and output volume. A premium 1940 radio would have a very large speaker in a large cabinet, engineered for fairly smooth frequency response, and with tone controls which could be adjusted for a limited frequency response for distant or noisy reception, or a wider response for a strong signal. Some radio programs in 1940 were studio presentations with a very low noise level and a good frequency response up to the high frequency limits applicable in the transmitter, to keep the signal within the allowed bandwidth. Premium radios were made to reproduce such broadcasts well. See [http://news.google.com/newspapers?id=XQViAAAAIBAJ&sjid=QpcDAAAAIBAJ&pg=4755,2516195&dq=fidelity+radio-receiver&hl=en] from 1938, which discusses "high fidelity" premium cost receivers selling for $200. In April 1940 you could buy a Stromberg FM receiver for $295 or less which would sound amazingly high fidelity, as in [http://news.google.com/newspapers?id=r04aAAAAIBAJ&sjid=3iQEAAAAIBAJ&pg=5698,2197708&dq=fidelity+radio-receiver&hl=en this ad]. Such a receiver would put to shame most modern radios of low or moderate cost. After WW2, the state of the art had obviously advanced even farther. [http://news.google.com/newspapers?id=Lk1hAAAAIBAJ&sjid=2nQNAAAAIBAJ&pg=3568,1866769&dq=fidelity+radio-receiver&hl=en Here] is a 1948 article about the quality of FM reception. The best modern radio would still outperform the best 1940's radio, by picking up FM stereo as well as through speaker and electronics advances, but a "cheap" modern radio would fall far short of a good 1940's radio. [[User:Edison|Edison]] ([[User talk:Edison|talk]]) 23:34, 9 February 2011 (UTC)
::::::::Fantastic links, Edison. [http://news.google.com/newspapers?id=Lk1hAAAAIBAJ&sjid=2nQNAAAAIBAJ&pg=3568,1866769&dq=fidelity+radio-receiver&hl=en "Even if you live next door to a man with an electric razor, your FM radio won't be bothered by it."] I suppose I've been selling FM radio short!! [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 23:57, 9 February 2011 (UTC)
:::::::::A good radio from the 1920's perfectly restored, required the tuning of two RF stages as well as adjustment of the filament voltage, to tune in a station. The sound came from a horn speaker, and was no better than the very cheapest small transistor radio. A late 1940's radio could sound very fine, indeed. [[User:Edison|Edison]] ([[User talk:Edison|talk]]) 05:29, 10 February 2011 (UTC)
Would the sound quality of an average radio in 2011 be better than that of an average 1940s radio? Would the sound quality of a large "stereo" 2011 radio with large speakers be better? I'm thinking of all the black and white American films from the 1940s, before people started watching television, where they play music on the radio. Ignoring the fact that its fiction, were they getting better, same, or worse sound quality than me? Thanks [[Special:Contributions/92.29.122.239|92.29.122.239]] ([[User talk:92.29.122.239|talk]]) 12:55, 10 February 2011 (UTC)
== largest bird egg ==
Which bird which can fly lays the largest eggs? [[User:Googlemeister|Googlemeister]] ([[User talk:Googlemeister|talk]]) 14:45, 9 February 2011 (UTC)
:If you allow mythical birds, then the [[roc]] would be a contender, (and the ostrich of course for living non-flying birds), but my guess would be a swan. Can anyone think of a larger? [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 16:23, 9 February 2011 (UTC)
::[[Kori Bustard]], ''Ardeotis kori'' is quite a bit larger than the swan. [[User:Dodger67|Roger]] ([[User talk:Dodger67|talk]]) 16:27, 9 February 2011 (UTC)
:::That's a much better answer. The [[Argentavis]] had an egg three times the weight of the swan egg (over a kilogram), but it is no longer around. [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 16:30, 9 February 2011 (UTC)
::::The Kori bustard is the heaviest flying bird today (I think), so, yes. But for egg size I might have to check. [[User:Crimsonraptor|Crimsonraptor]] | [[User talk:Crimsonraptor|(Contact me)]] <small>[[Special:Contributions/Crimsonraptor|Dumpster dive if you must]]</small> 16:41, 9 February 2011 (UTC)
:::::[[Andean condor]]s have an egg weight of 280 grams or so, and the egg length is around 4 inches. So is that the record, then? [[User:Crimsonraptor|Crimsonraptor]] | [[User talk:Crimsonraptor|(Contact me)]] <small>[[Special:Contributions/Crimsonraptor|Dumpster dive if you must]]</small> 16:44, 9 February 2011 (UTC)
::::::The swan beats that with an egg weight of up to 340 grams, but I expect the Kori Bustard (paauw, Ardeotis Kori) egg is heavier, and the European Great Bustard ((Otis tarda) would also be a contender. Can anyone find a reference? The eggs of the Elephant Bird, or Vouron Patra (Aepyornis maximus) were the largest ever (bigger than any dinosaur egg), in fact they reached the physical limit of structural integrity for an egg-shape made of shell. [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 21:53, 9 February 2011 (UTC)
:::::::<small>This reply to the condor claim was added after the reply below, but it is also a reply to Quetzalcoatlus claim. [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 22:17, 9 February 2011 (UTC) </small>
::::::::[[Elephant bird]]. [[Special:Contributions/92.29.122.239|92.29.122.239]] ([[User talk:92.29.122.239|talk]]) 12:59, 10 February 2011 (UTC)
:::::::::Elephant birds were flightless 92. [[User:Googlemeister|Googlemeister]] ([[User talk:Googlemeister|talk]]) 14:17, 10 February 2011 (UTC)
::: The eggs of [[Quetzalcoatlus]] must have been enormous. There has been an increasingly common recent suggestion that modern birds descended from dinosaurs. [[Special:Contributions/2.97.217.143|2.97.217.143]] ([[User talk:2.97.217.143|talk]]) 20:22, 9 February 2011 (UTC)
::::If by "increasingly common recent suggestion" you mean "we're as sure about it as we can be"... It's pretty much established and accepted that birds are descended from dinosaurs. --[[User:Jayron32|<font style="color:#000099">Jayron</font>]]'''''[[User talk:Jayron32|<font style="color:#009900">32</font>]]''''' 00:06, 10 February 2011 (UTC)
::::AFAIK, there weren't any flying dinosaurs, besides the early birds. --[[User:TotoBaggins|Sean]] 15:16, 10 February 2011 (UTC)
== why is AIDS so hard to cure? ==
if it's just a virus, a bit of DNA, shouldn't it be really easy to cure instead of really hard? It's not like cancer, of which there are all these different types... it's just a piece of arguably not even living DNA... [[Special:Contributions/217.136.92.148|217.136.92.148]] ([[User talk:217.136.92.148|talk]]) 15:12, 9 February 2011 (UTC)
:If you read the Article on [[HIV]] ([[AIDS]] is but an expression of HIV infection in its latter stages) you will see that this simple Virus is firstly attacking one of the vital parts involved in defeating "usual" viruses in the human body secondly has a high genetic variability (Theres all kinds of different kinds), making it very hard to attack by "conventional means". These two among many other things are making this "simple infection" such a challenge to science. The articles are really quite informative. --[[Special:Contributions/147.142.185.92|147.142.185.92]] ([[User talk:147.142.185.92|talk]]) 15:19, 9 February 2011 (UTC)
::Also, viral infections in general are much harder to cure than bacterial infections. See [[antiviral drug]]. In general, we only slow the virus down while the immune system adapts itself to do the actual curing. In the case of HIV, the immune system itself is attacked by the virus. --[[User:Stephan Schulz|Stephan Schulz]] ([[User talk:Stephan Schulz|talk]]) 15:47, 9 February 2011 (UTC)
:::Is it possible to use nanotechnology to do the actual curing instead? [[User:ScienceApe|ScienceApe]] ([[User talk:ScienceApe|talk]]) 17:20, 9 February 2011 (UTC)
::::If it were, AIDS would be cured already. --[[User:TotoBaggins|Sean]] 15:17, 10 February 2011 (UTC)
That's ridiculous. A virus is a piece of code, exactly the same as a binary executable on Windows, the sole difference being that instead of binary it's in quadrinary - you would need two bits to code each base pair. Now you're telling me that it's polymorphic. Fine. Does Norton etc. give up when a piece of code is polymorphic? No way. You're telling me, however, that we don't do any scanning of virus code whatsoever, in any way. We just slow down execution of it, so that the body's own antivirus can adapt to it! That's ridiculous. Imagine if all "Norton" did was run one very tight loop on all cores, and seek to random parts of the hard-drive, in an attempt to slow down the spread of the virus enough for Windows to catch up to it. That's ridiculous. Give me one good reason the human body couldn't have an artificial antivirus just like Windows can have a third-party one. The idea of having to use the body's immune system is just beyond comprehension for me. Why can't viruses be cured through artificial means -t hey're just a bit of code that, frankly, is not even alive. (Though this is in dispute.) [[Special:Contributions/217.136.92.148|217.136.92.148]] ([[User talk:217.136.92.148|talk]]) 16:25, 9 February 2011 (UTC)
:Re-writing DNA codes is a very new science, and we cannot even cure the common cold yet. The difference between Norton anti-virus and curing AIDS is that there are millions of copies of the AIDS virus, and we can't (yet) get at all of them, especially in cells deep in the body, so we can't just remove that bit of code from all the infected cells. [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 16:40, 9 February 2011 (UTC)
:If we contuinue to use the (frankly quite ridiculous) computer virus metaphor that the OP seens to have some understanding of: The problem with fighting HIV the way Norton's fights a computer virus is that if HIV was a computer virus the first thing it does when it runs is to delete the Norton's scanning executable. The human body is not a computer so the analogy is seriously limited. [[User:Dodger67|Roger]] ([[User talk:Dodger67|talk]]) 16:47, 9 February 2011 (UTC)
:In addition to the immune system depression, one of the issues with HIV is that it's a [[retrovirus]]. That is, it actually incorporates it's DNA into the genome. All DNA looks the same, so once it's incorporated, there really isn't any difference chemically between HIV DNA and Human DNA. You can kill off the existing virus particles, and you might even kill off the cells which are producing virus proteins, but it is hypothesized that there are always "reservoir" cells which contain viral DNA, but aren't producing any viral proteins or RNA (until they are activated later). There's no way you can tell these reservoir cells from healthy cells unless you had a way to read and interpret the sequence of DNA, and we don't currently have ways of doing that, at least while the DNA is still in the cell. All the drugs and treatments we currently have either work on the protein or RNA level, or they attack all DNA indiscriminately, regardless of sequence. Programs like Norton Antivirus work because they have tools which can read the file sequences and compare those to viral signatures. We don't have anything like that for reading and comparing DNA sequences in the body. We have to rely on the natural decoding ability of the [[ribosome]], or the cell's own DNA binding proteins to do sequence recognition. There's hopes that we'll eventually be able to do genome editing with [[zinc finger nuclease]]s, designed [[homing endonuclease]]s, or even [[Lexitropsin|sequence specific small molecule binders]], but we don't have any of those yet. -- [[Special:Contributions/174.24.195.38|174.24.195.38]] ([[User talk:174.24.195.38|talk]]) 17:24, 9 February 2011 (UTC)
::Actually, we don't know how to cure a single viral disease. We can immunize viral diseases and offer supportive care, and boost the bodies natural defenses but humanity has yet to actually cure viral diseases like we can some bacterial infections. [[User:Googlemeister|Googlemeister]] ([[User talk:Googlemeister|talk]]) 17:48, 9 February 2011 (UTC)
:: Thanks for that informative answer, which means you got my metaphor, unlike the person above you who thought I wanted the antivirus to run on the body's own immune system. So, you say we can't edit DNA in cells. But tell me this: if we could edit DNA in cells, then we could neutralize HIV in 1 cell or 2, or 10, 100, 1000, whatever. In fact, how many cells would have the HIV dna in a real case? Millions? Billions? I remember that there are between 10 and 100 trillion cells in the human body, depending on who you ask. How many of those would have hiv dna in them, in an infected patient? Which kinds of cells would have that DNA? Would cells, like bone cells, or brain neuron cells, have that DNA, which are totally impractical to replace? Or, on the contrary, would all the cells that have that DNA be of a kind that, in theory, you could replace... Thanks. [[Special:Contributions/217.136.92.148|217.136.92.148]] ([[User talk:217.136.92.148|talk]]) 18:18, 9 February 2011 (UTC)
::: There ''may be'' an answer,<sup>[http://www.technologyreview.com/blog/arxiv/24331/]</sup> but developing it means perfecting the most terrible, insidious, and versatile weapon of assassination, mass destruction, genocide, and Orwellian surveillance ever conceived by the hand of man. Then again, the U.S. Army is beginning work on that anyway.<sup>[http://www.acq.osd.mil/osbp/sbir/solicitations/sbir101/cbd101.htm]</sup> [[User:Wnt|Wnt]] ([[User talk:Wnt|talk]]) 18:58, 9 February 2011 (UTC)
:The common cold is "just" a virus, and we can't even cure that. [[User:Ndteegarden|thx1138]] ([[User talk:Ndteegarden|talk]]) 19:46, 9 February 2011 (UTC)
:The computer virus analogy breaks down on several important levels. First and most importantly: computer code can be stopped, it can be forced to cease execution then operated on discreetly and perfectly. You can't put the human body into a stable 'non-executing code' state, read it, scan it and arbitrarily edit the 'code'. Also key is the fact there's no way to stop the DNA from "executing" short of stopping biological processes entirely, not even killing the patient would do that. Secondly, there's no way to freely, arbitrarily and discreetly remove sections of DNA from a larger strand on-the-fly in vivo, if you could do that AIDS would be an utterly trivial problem yes, but so would death itself. [[Special:Contributions/65.29.47.55|65.29.47.55]] ([[User talk:65.29.47.55|talk]]) 01:17, 10 February 2011 (UTC)
:: Could you explain why "death itself" would become a trivial problem if we could do that? [[Special:Contributions/109.128.101.244|109.128.101.244]] ([[User talk:109.128.101.244|talk]]) 11:45, 10 February 2011 (UTC)
::<small>A mechanic was removing a cylinder-head from the motor of a Dodge SRT-4 when he spotted a well-known cardiologist in his shop. The cardiologist was there waiting for the service manager to come take a look at his car when the mechanic shouted across the garage "Hey Doc, want to take a look at this?". The cardiologist, a bit surprised, walked over to where the mechanic was working on the SRT. The mechanic straightened up, wiped his hands on a rag and asked, "So Doc, look at this engine. I open its heart, take the valves out, repair any damage, and then put them back in, and when I finish, it works just like new. So how can I make 39,675 a year, a pretty small salary, and you get the really big bucks, $1,695,759, when you and I are doing basically the same work?". The cardiologist paused, smiled and leaned over, then whispered to the mechanic, "Try doing it with the engine running." -</small> [[User:Ranemanoj|manya]] ([[User talk:Ranemanoj|talk]]) 03:50, 10 February 2011 (UTC)
== high protein consumption and kidney damage in humans ==
In humans, what is the correlation and regression curve between kidney damage and the consumption of high levels of protein (200 to 600 grams per day) to meet the basal metabolic rate (BMR)? --[[User:Inning|Inning]] ([[User talk:Inning|talk]]) 16:28, 9 February 2011 (UTC)
:Please excuse me if I'm wrong, but that has the look of a homework problem. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 18:44, 9 February 2011 (UTC)
::LOL... was just trying to phrase it so no one would say "We can't give medical advice." Next time just say you need to cover your ass since you do not know the answer to the question. --[[User:Inning|Inning]] ([[User talk:Inning|talk]]) 01:14, 10 February 2011 (UTC)
:::Well, now I'm confused. Do you need some kind of data plot, or do you just want to know how protein-focused a diet needs to be in order to cause kidney damage? [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 05:02, 10 February 2011 (UTC)
== [[Dirty talk]] ==
I have two questions on [[dirty talk]] - 1. Psychology of dirty talk, 2. Evolutionary origin of dirty talk.
1. What is the psychology behind [[dirty talk]]?
2. According to the article [[Origin_of_language#Homo_sapiens|Origin of language]], "The development of fully modern behavior in H. sapiens, not shared by H. neanderthalensis or any other variety of Homo, is dated to some 70,000 to 50,000 years ago. The development of more sophisticated tools, for the first time constructed out of more than one material (e.g. bone or antler) and sortable into different categories of function (such as projectile points, engraving tools, knife blades, and drilling and piercing tools) are often taken as proof for the presence of fully developed language". So, how did Homo sapiens did dirty talk before the advent of language? What is the evolutionary origin of dirty talk? --[[User:Dolyop|Dolyop]] ([[User talk:Dolyop|talk]]) 16:31, 9 February 2011 (UTC)
:1. It turns some people on to speak it, it turns some people on to hear it. When those people get together, everyone is happy.
:2. There's really no way to know for certain since spoken language (or proto-language) can't fossilize, but giving signals of sexual availability is an extremely ancient and very basic form of communication among animals. Talking dirty would be part of that continuum, so even if we had a time machine it would be tough to draw a line somewhere. [[User:Matt Deres|Matt Deres]] ([[User talk:Matt Deres|talk]]) 18:35, 9 February 2011 (UTC)
== Teleporting particles ==
According to the Heisenberg Uncertainty Principle, and Quantum Tunneling, particles like protons and electrons are essentially disappearing from reality and reappearing in reality in a different position. Would it be fair to say that these particles are essentially teleporting? Do neutrons also exhibit this behavior? [[User:ScienceApe|ScienceApe]] ([[User talk:ScienceApe|talk]]) 18:55, 9 February 2011 (UTC)
:In quantum mechanics there is no underlying "reality" in which every particle has a definite ___location at every moment. If you drop the concept of "reality", I think you'll find that there is no way even to ask your question. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 19:21, 9 February 2011 (UTC)
:: I think if you drop the concept of "reality", there is no way to even ask any question. [[Special:Contributions/109.128.101.244|109.128.101.244]] ([[User talk:109.128.101.244|talk]]) 19:49, 9 February 2011 (UTC)
::: This usage of "teleporting" would be more confusing than enlightening. In almost ''every single atom'' (excepting hydrogen and helium) there are "nodes" where the probability of finding an electron by experiment drops to zero. Do all these electrons "teleport" when they cross these nodes? In your case, you might suppose that the particle doesn't exist inside a barrier of finite width, but in truth the [[quantum amplitude]] ''does'' penetrate the barrier (see figure in [[quantum tunneling]]). It is only that classically, the particle doesn't have the energy to be there. [[User:Wnt|Wnt]] ([[User talk:Wnt|talk]]) 20:35, 9 February 2011 (UTC)
::::I think there's no conundrum if you recognize that the ''[[wave function]]'' isn't ''the particle.'' The wave function is only a theoretical description that models certain aspects of the particle's behavior. "Where is the particle" is ''not'' word-for-word interchangeable with "where is the value of <math>|\Psi^2|</math> nonzero." The conceptual paradox of "teleporting" across energy barriers is only a problem if you try to equate "particle position" and "wavefunction" in a classical sense. [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 21:33, 9 February 2011 (UTC)
:This would be less confusing if they simply weren't ''called'' particles. If they were called waves, the uncertainty principle and tunneling wouldn't be so surprising, because they also show up in classical wave theories. [http://www.phys.unsw.edu.au/jw/uncertainty.html This page] (which I found with a five-second Google search and haven't carefully examined) describes the classical frequency-time uncertainty principle for sound waves. An example of classical tunneling is the leakage of light between two fiber-optic cables separated by a small amount of air, even when the light is totally internally reflected. This is called [[evanescent wave coupling]] or [[frustrated total internal reflection]], but it might as well be called tunneling (or the quantum version might as well be called evanescent coupling). Quantum mechanics is a unification of classical wave and classical particle theories. The unification is new, but practically every quantum phenomenon shows up in one or the other type of classical theory. The wave phenomena are the ones that are usually called "weird", but that's an arbitrary judgment. -- [[User:BenRG|BenRG]] ([[User talk:BenRG|talk]]) 04:53, 10 February 2011 (UTC)
== Other phases of ice at room temperature ==
At room temperature, ice I will melt. Will any of the other forms of ice not melt at room temperature (as diamond does not)? [[Special:Contributions/128.223.222.68|128.223.222.68]] ([[User talk:128.223.222.68|talk]]) 19:51, 9 February 2011 (UTC)
: What do you mean by "other forms of ice"? Water has a melting point of 0 °C (at sea level). Diamonds are made of carbon, which has a melting point of 3500 °C. [[User:Ndteegarden|thx1138]] ([[User talk:Ndteegarden|talk]]) 19:54, 9 February 2011 (UTC)
: http://en.wikipedia.org/wiki/Ice#Phases may be usefull to you [[Special:Contributions/83.134.177.191|83.134.177.191]] ([[User talk:83.134.177.191|talk]]) 20:12, 9 February 2011 (UTC)
:According to our article, [[Ice_VII]] can remain solid at high temperatures. Also "...ice VII has the largest stability field of all of the molecular phases of ice"... [[Vonnegut]]'s 'ice 9' notwithstanding. [[User:SemanticMantis|SemanticMantis]] ([[User talk:SemanticMantis|talk]]) 20:23, 9 February 2011 (UTC)
::Of course, to have Ice VII, you would need to have a means to exert 10 gigapascals of pressure. [[User:Googlemeister|Googlemeister]] ([[User talk:Googlemeister|talk]]) 20:55, 9 February 2011 (UTC)
:There is also the FICTIONAL [[Ice-nine]]. [[User:Dauto|Dauto]] ([[User talk:Dauto|talk]]) 23:28, 9 February 2011 (UTC)
::I interpret this question as asking what solid materials would melt at room temperature (using "ice" in a looser sense as a crystal solid of some type). The answer is of course anything that's liquid at room temperature will melt at room temperature if you take a solid block of it out of the freezer. [[Mercury (element)]], for example, as in [http://www.youtube.com/watch?v=apijzIKrTeM this video]. Pure "Glacial" [[Acetic Acid]]'s melting point is just below room temperature (16 C/62 F), and will indeed melt if brought into a warm room in a frozen state. It actually looks pretty similar to water ice: [http://www.sciencephoto.com/images/download_wm_image.html/A500260-Ethanoic_acid-SPL.jpg?id=655000260] Perhaps 128.223 needs to clarify their question. [[User:Buddy431|Buddy431]] ([[User talk:Buddy431|talk]]) 00:00, 10 February 2011 (UTC)
:::I thought the question was clear. It is asking, if you start with water and apply suitable pressure and temperature to convert it to a different phase (such as ice VII), is it possible to achieve a phase that will remain solid at room temperature and (I presume this was intended) ordinary pressure? (Just as you might convert graphite to diamond and the diamond remains stable.) As I understand it the answer is no; water phases like ice VII will not remain stable when the pressure is removed. --Anonymous, 06:10 UTC, February 10, 2011.
== Natural hazards and natural disasters humid continental climate ==
Which natural hazards and natural disasters are associated with Humid continental climate? <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/65.95.106.36|65.95.106.36]] ([[User talk:65.95.106.36|talk]]) 20:29, 9 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:Since this has the look of a homework question, I'll respond by suggesting that you look at our article on [[humid continental climate]] and ask yourself what bad things can happen in the places it shows. The fact that you live in one of them should be helpful. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 20:50, 9 February 2011 (UTC)
== Metabolism of alcohol ==
I am trying to figure out how the body is able to get so much caloric value from ethanol. the way that I understand it is that the body absords it directly into the blood stream unchanged. Alcohol is then converted to acetaldehyde by alcohol dehydrogenase. From there is it further metabolized to acetate and then to CO2 and water. Most of the alcohol is methabolized in the liver, and I have read that some of the metabolic conversons are very exothermic. How does the liver make use of these exothermic reactions to give alcohol so many dietary calories per gram?--[[Special:Contributions/160.36.38.218|160.36.38.218]] ([[User talk:160.36.38.218|talk]]) 20:36, 9 February 2011 (UTC)
:I think you're missing the most important step. As our [[ethanol metabolism]] article explains, acetic acid is metabolized to acetyl-CoA, which can be used as an energy source in many parts of the body via the [[citric acid cycle]]. [[User:Looie496|Looie496]] ([[User talk:Looie496|talk]]) 20:57, 9 February 2011 (UTC)
So it is this step that makes it 1/3 better store of energy than sugar?--[[Special:Contributions/69.245.43.176|69.245.43.176]] ([[User talk:69.245.43.176|talk]]) 21:41, 9 February 2011 (UTC)
:I haven't checked your number with the biochemistry, but it seems plausible. High calorie fats or fossil fuels are typically -(CH2)- repeatedly with no oxygen added. Ethanol is CH3CH2OH - one oxygen per two carbons. Sugars are generally -(CHOH)- over and over, in other words, there is already one oxygen combined with each carbon. Now two oxygens per carbon is CO2. So you can think of ethanol as being (very roughly) gasoline that is 1/4 burnt, and sugar as gasoline 1/2 burnt; take (3/4 left) / (1/2 left) and you have your 3:2 ratio. (I omit in this that ethanol has an extra H2 at the ends, because it is short, and that fats sometimes omit H2s when unsaturated, etc. - to do this precisely you have to go through [[glycolysis]], the [[Krebs cycle]], [[oxidative phosphorylation]] and related processes in painstaking detail, and it turns out that you often won't get one single certain number even if you do!) [[User:Wnt|Wnt]] ([[User talk:Wnt|talk]]) 22:38, 9 February 2011 (UT
::If you look at the energy budget of metabolizing glucose through glycolysis and oxidative phosphorylation, you see that only 2 [[ATP]]s are produced per molecule of glucose in glycolysis, but 30-36 ATPs are produced by the oxydative phosphorylation of the two [[acetyl-CoA]]s that are formed per glucose molecule and the [[NADH]] formed during glycolysis. One molecule of ethanol is turned into one of acetyl-CoA, and the [[alcohol dehydrogenase]] and [[aldehyde dehydrogenase]] create enough NADH to balance those formed by glycolysis. Two ethanol molecules thus only lose 2 out of 32-38 ATPs that are formed from one molecule of glucose. Because they are lighter than one glucose molecule, the calories per gram figure works out to be about the same (if not a bit higher for ethanol). -- [[Special:Contributions/140.142.20.229|140.142.20.229]] ([[User talk:140.142.20.229|talk]]) 23:05, 9 February 2011 (UTC)
== Largest phytosaur ==
I've been doing a bit of research for an illustration I'm making, which has a large [[phytosaur]] in it. In fact, quite large. [http://www.ucmp.berkeley.edu/taxa/verts/archosaurs/parasuchia.php This page] from the [[UCMP]] website states the largest grew up to {{convert|12|m|ft}}, which nails my illustration, but doesn't give the species. Could anyone here help, because most of our articles don't give a size estimate? Thanks! [[User:Crimsonraptor|Crimsonraptor]] | [[User talk:Crimsonraptor|(Contact me)]] <small>[[Special:Contributions/Crimsonraptor|Dumpster dive if you must]]</small> 22:35, 9 February 2011 (UTC)
:Looks like that would be ''[[Smilosuchus]]'' [http://www.carnivoraforum.com/index.cgi?board=interspecific&action=print&thread=6958] [[Special:Contributions/75.41.110.200|75.41.110.200]] ([[User talk:75.41.110.200|talk]]) 15:04, 10 February 2011 (UTC)
== Why does snow melt on cold days? ==
I've always been puzzled that snow melts on sunny days when the temperature is below freezing. It's 13°F today, how is the sun making the snow melt? --[[Special:Contributions/68.102.163.104|68.102.163.104]] ([[User talk:68.102.163.104|talk]]) 23:00, 9 February 2011 (UTC)
:When snow is in direct sunlight, it can melt even when the air temperature is lower than freezing. --<span style="text-shadow:grey 0.3em 0.3em 0.1em">'''[[User:THFSW|<font color="black">T H F S W</font>]]''' (''[[User talk:THFSW|T]] '''·''' [[Special:Contributions/The High Fin Sperm Whale|C]] '''·''' [[Special:EmailUser/The High Fin Sperm Whale|E]]'')</span> 23:01, 9 February 2011 (UTC)
::Agreed, sunlight can raise the temperature of snow or ice several degrees. Sunlight can also reflect off a building and increase the intensity on the snow. If the snow is on the sidewalk or street, the dark color of the concrete or asphalt may cause it to heat up above the freezing point. If ice melter or road salt has been spread, that greatly lowers the melting point of the snow or ice and causes it to liquify and thus hastens its evaporation. Sublimation can take snow directly from its solid form to vapor form. [[User:Edison|Edison]] ([[User talk:Edison|talk]]) 23:21, 9 February 2011 (UTC)
:::A similar effect can be seen in [[Auto-defrost]] freezers (pretty much every freezer on the market these days), even thought the temperature IN the freezer never goes above freezing, the freezer creates conditions (mainly by circulating dry air) where unsealed ice cube trays will eventually [[sublimate]] away to nothing. [[User:Vespine|Vespine]] ([[User talk:Vespine|talk]]) 23:33, 9 February 2011 (UTC)
== Where should post this? I am NOT happy with the physics sections of wikipedia. ==
Wikipedia needs a lock down on its basic definitions of physics after a thorough review by PhD professionals.
The articles are MISLEADING and students interested in physics are getting bad advice.
I am re-interested in physics and science after studying it many years ago and see many errors between my degree level textbook and basic definitions that are in Wikipedia.
For example the "conservation of mass" article starts to fall apart on the second paragraph, and the reader is left with the impression of a vague law that doesn't really work. There is a huge tendency to lump in classical, special relativity and quantum theory all in the same article which is really confusing to the layman ESPECIALLY when it is in the SECOND paragraph.
Also check out the opening paragraph of "energy", nice examples ? easy to understand?
{{unsigned|92.17.89.69}}
:The [[WT:PHYSICS|physics wikiproject]] would be better than here, but please remember that we are all volunteers and that if you find something unsatisfactory, the simplest thing to do is to [[WP:SOFIXIT|fix it yourself]]. If you get stuck on something I'm sure there are plenty of people who can help you. [[User:Smartse|SmartSE]] ([[User talk:Smartse|talk]]) 23:14, 9 February 2011 (UTC)
:I will also point out that Wikipedia seeks to be an ''[[encyclopedia]]''. As such, it is ''not'' a replacement for a physics textbook or a physics class. Are you looking for a physics textbook? We can recommend numerous different authors, subjects, and depth-levels, depending on your need. [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 23:19, 9 February 2011 (UTC)
:: You should write a letter to their offices and request a refund, citing your dissatisfaction. You could also leave a negative review of the encyclopedia on Amazon, to discourage others from buying it. In the meantime, you should go to their competition, Britannica. [[Special:Contributions/109.128.101.244|109.128.101.244]] ([[User talk:109.128.101.244|talk]]) 23:28, 9 February 2011 (UTC)
:::<small>[[WP:BITE|Please don't bite the newcomers]]. [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 00:09, 10 February 2011 (UTC) </small>
:If you'd like to improve the article, please do — anyone, even you, can improve any article on Wikipedia. [[User:Comet Tuttle|Comet Tuttle]] ([[User talk:Comet Tuttle|talk]]) 23:39, 9 February 2011 (UTC)
:It is our policy for the introduction (or [[WP:LEDE|lede]]) of an article to summarise the whole article. That means the introduction to the article on conservation of mass does need to cover classical mechanics as well as relativistic mechanics, so they are both important enough topics to be covered in the article. --[[User:Tango|Tango]] ([[User talk:Tango|talk]]) 00:13, 10 February 2011 (UTC)
::Yeah, Tango, but the OP still has a point. Just because the lede has to summarize the whole article doesn't mean that it can't do so in a way that is easy to read and understand. The physics and other technical artilcles at Wikipedia are basically impenetrable for anyone without advanced training; which is kinda silly since the articles are often written so that the only people who can understand the article are people who don't actually need to read it because they already understand the concepts being discussed! I fully understand the OP's frustration because I share that frustration. Take a look at [[Magnetization]] for example. Lets say you were an English major in college, but still want to know a bit more how magnetization works. That article does you no good. Which is not to say that the techinical detail could not also be in those articles. It absolutely should be. Its just that there needs to be more attention given towards explaining concepts like [[conservation of mass]] and [[magnetization]] to people who may actually want to learn something from the articles. --[[User:Jayron32|<font style="color:#000099">Jayron</font>]]'''''[[User talk:Jayron32|<font style="color:#009900">32</font>]]''''' 01:02, 10 February 2011 (UTC)
:::I agree. I think wikipedia has a few excellent physics articles, true, but it also has many that are not directed to the general public and if the reader doesn't already understand the topic, he is unlikely to learn anything new. [[User:Dauto|Dauto]] ([[User talk:Dauto|talk]]) 02:29, 10 February 2011 (UTC)
::::As your hypothetical English-major-ish kind of person, I definitely agree with that [[Magnetization]] has problems. I didn't see why it needed the equation to be in the second line, or even to introduce the abbreviations M and V at that point. It would benefit from a simple change to: "In physics '''magnetization''' is...". This is a pure guess, but is magnetization actually ''how magnetic'' a piece of steel is? I.e. if I acquire a magnet and then leave it alone for a long time, it will become less magnetic. [[User:Itsmejudith|Itsmejudith]] ([[User talk:Itsmejudith|talk]]) 13:11, 10 February 2011 (UTC)
:::::[[Conservation of mass]] delves into the history of science, but doesn't do it well. Some is unsourced, other sources may be primary. There is a great leap from the 18th century to relativity, and the relativity is introduced simply by references to main articles. [[User:Itsmejudith|Itsmejudith]] ([[User talk:Itsmejudith|talk]]) 13:18, 10 February 2011 (UTC)
Wikipedia is ONLY for the casual whatever-ist and as such it should be compiled as if it were for a highschool freshman not a college grad. If the authors edited with this in mind, I think many more people would find Wikipedia useful. <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/165.212.189.187|165.212.189.187]] ([[User talk:165.212.189.187|talk]]) 14:14, 10 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
== clay ==
is it true that ceramic dinner plates have crushed glass added to the clay?--[[User:Tomjohnson357|Tomjohnson357]] ([[User talk:Tomjohnson357|talk]]) 02:33, 10 February 2011 (UTC)
:Some might. --[[User:Jayron32|<font style="color:#000099">Jayron</font>]]'''''[[User talk:Jayron32|<font style="color:#009900">32</font>]]''''' 03:49, 10 February 2011 (UTC)
::Well, by that reasoning, "some might" have just about anything added to the clay. We do have an article on [[Ceramic]] which seems to indicate that crushed glass is not a necessary, or even common component of ceramic. In fact, it also states that for modern ceramics, even clay is not a necessary component. The relevant article is [[Ceramic materials]] which further states ''Glass by definition is not a ceramic because it is an amorphous solid (non-crystalline).'' [[User:Vespine|Vespine]] ([[User talk:Vespine|talk]]) 04:04, 10 February 2011 (UTC)
:::Or are you asking if plates that are "advertised" as ceramic sometimes [[adulterated]] with crushed glass? I have no answer for that question. [[User:Vespine|Vespine]] ([[User talk:Vespine|talk]]) 05:26, 10 February 2011 (UTC)
:: On the other hand the [[Ceramic]] article states: "Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous (e.g., a glass)". And [[Porcelain]] directly attributes some of the properties of porcelain to glass formation.
:: Also, is it even relevant for the finished product whether the original mixture included glass powders? If I understand correctly, the components of the body will partially melt and re-crystallize during firing anyway, and the final structure generally consists of crystalline particles held together by a glassy matrix.
:: The [[soft-paste porcelain]] article mentions that ground-up glass has been used in porcelain formulations. –[[User:Henning Makholm|Henning Makholm]] ([[User talk:Henning Makholm|talk]]) 10:32, 10 February 2011 (UTC)
== crude oil ==
why price gap between WTI crude oil and BRENT crude oil is widening ?? <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/121.245.239.36|121.245.239.36]] ([[User talk:121.245.239.36|talk]]) 09:06, 10 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:The ansewer is in the field of Economics, not Science, your question is in the wrong place. [[User:Dodger67|Roger]] ([[User talk:Dodger67|talk]]) 09:17, 10 February 2011 (UTC)
:: Yeah, that's why they call Economics the "dismal humanity". [[Special:Contributions/109.128.101.244|109.128.101.244]] ([[User talk:109.128.101.244|talk]]) 11:39, 10 February 2011 (UTC)
::We don't have an economics reference desk Roger. [[User:ScienceApe|ScienceApe]] ([[User talk:ScienceApe|talk]]) 14:50, 10 February 2011 (UTC)
== Price for quantitative analysis of chemical elements ==
Say I have 1g of a substance and I want to know which elements are contained in what quantities. I'm not interested in molecules or cristall structures or such. As result, I want to have a list that reads, for example, like this: C 400mg, O 150mg, N 30mg, H 20mg, S 3mg, Si 2mg, .... Ni 3µg, As 1.2µg etc. .
How much would such an analysis cost and which methods would be used? [[Special:Contributions/77.3.134.134|77.3.134.134]] ([[User talk:77.3.134.134|talk]]) 10:20, 10 February 2011 (UTC)
:Depending on the accuracy you need it could be very cheap. [[Energy-dispersive X-ray spectroscopy]] would be the trick for every thing in down to the 1% range. Going down to ppm it is expensive.--[[User:Stone|Stone]] ([[User talk:Stone|talk]]) 10:32, 10 February 2011 (UTC)
::Five percent for each amount (factor 0.95 to 1.05, not percent of the total sample mass) would be fine. What, approximately, would mean "cheap" in this context? [[Special:Contributions/77.3.134.134|77.3.134.134]] ([[User talk:77.3.134.134|talk]]) 10:52, 10 February 2011 (UTC)
:::The general field is [[elemental analysis]]. That article mentions several methods. There are many companies that will do contract-work analysis of customer samples--a quick google or business-directory search involving the (quoted) phrase might find some with rates posted (or at worst, would give a ballpark over the phone/email) for various levels of accuracy. [[User:DMacks|DMacks]] ([[User talk:DMacks|talk]]) 15:18, 10 February 2011 (UTC)
== biology ==
what is the function of crop sac fluid in pigeon? <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/180.215.15.1|180.215.15.1]] ([[User talk:180.215.15.1|talk]]) 12:36, 10 February 2011 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:We have a article on [[Crop milk]]! Is this enough info? --[[User:Stone|Stone]] ([[User talk:Stone|talk]])
== Cells in chicken eggs ==
When a chicken egg pops out of a chicken, how many cells does it have in it? I do not believe that it can be just one giant cell, as some people seem to think. Thanks [[Special:Contributions/92.29.122.239|92.29.122.239]] ([[User talk:92.29.122.239|talk]]) 13:04, 10 February 2011 (UTC)
: Would you believe 2? Or, if not 2, then -- since, to be fair, the egg ''is'' a single cell -- what is the lowest number of cells you will accept as an answer? [[Special:Contributions/109.128.101.244|109.128.101.244]] ([[User talk:109.128.101.244|talk]]) 15:18, 10 February 2011 (UTC)
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