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'''Thealogy''' is literally the study of the [[Goddess]] ([[Greek language|Greek]] θεά, ''thea'', "goddess" + λόγος, ''logos'', "study"). In [[1993]], [[Charlotte Caron]]'s definition of '''thealogy''' as "reflection on the divine in feminine and feminist terms" appeared, but the term actually originates in the writings of [[Isaac Bonewits]] in [[1974]].
[[image:Blueglow.jpg|frame|[[Cherenkov effect]] in a "swimming pool" [[nuclear reactor]]. The effect is due to [[electron]]s moving faster than the speed at which light moves in water.]]
==First uses==
The '''speed of light''' in a [[vacuum]] is exactly equal to [[1 E8 m|299,792,458]] [[metres per second]] (1,079,252,848.8 km/h and approximately 186,282.4 [[mile|miles]] per second). The speed of [[light]] is denoted by the letter ''c'', reputedly from the [[Latin]] ''celeritas'', "[[speed]]", and also known as [[Albert Einstein|Einstein]]'s constant. This exact speed is a definition, not a measurement, as the [[metre]] itself is defined in terms of the speed of light and the [[second]]. The speed of light through a medium (that is, not in vacuum) is less than ''c'' (defining the [[refractive index]] of the medium). "Speed of light" is sometimes abbreviated SOL.
===First(?) usages===
==Overview==
According to standard modern [[physics|physical theory]], all [[electromagnetic radiation]], including [[visible light]], propagates (or moves) at a constant speed in a vacuum, commonly known as the speed of light, which is a [[physical constant]] denoted as ''c''. This speed ''c'' is also the speed of propagation of [[gravity]] in the theory of [[general relativity]].
In "The Druid Chronicles (Evolved)," privately published in [[1976]], Isaac Bonewits used "thealogian" to refer to a Wiccan author ([[Aidan Kelly]], aka "C. Taliesin Edwards," who may have given him the term or vice versa) and "theilogy" (defined as "the study of more than one God"). Bonewits also used "theilogy" (and possibly "thealogy," since he thinks he coined them at the same time) in the pages of the widely-distributed "Gnostica" magazine he edited in 1974 and [[1975]].
One consequence of the laws of electromagnetism (such as [[Maxwell's equations]]) is that the speed ''c'' of electromagnetic radiation does not depend on the velocity of the object emitting the radiation; thus for instance the light emitted from a rapidly moving light source would travel at the same speed as the light coming from a stationary light source (although the colour, frequency, energy, and momentum of the light will be shifted, which is called the [[relativistic Doppler effect]]). If one combines this observation with the [[principle of relativity]], one concludes that all observers will measure the speed of light in vacuum as being the same, regardless of the [[frame of reference|reference frame]] of the observer or the velocity of the object emitting the light. Because of this, one can view ''c'' as a fundamental [[physical constant]]. This fact can then be used as a basis for the theory of [[special relativity]]. It is worth noting that it is the constant speed ''c'', rather than light itself, which is fundamental to special relativity; thus if light is somehow manipulated to travel at more or less than ''c'', this will not directly affect the theory of special relativity.
Observers travelling at large velocities will find that distances and times are distorted ("dilated") in accordance with the [[Lorentz transforms]]; however, the transforms distort times and distances in such a way that the speed of light remains constant. A person travelling near the speed of light would also find that colours of lights ahead were [[blue shift]]ed and those of those behind were [[red shift]]ed.
"The Druid Chronicles (Evolved)" were a three-year project starting in 1974 and finished (published) in 1976. The article referred to within "The Druid Chronicles (Evolved)" is dated to the summer of 1976. Moreover, this is almost certainly not the first usage; the context of "thealogian" is in citing a work by C. Taliesin Edwards, "Essays towards a Meta''thealogy'' of the Goddess." [stress added] There is, however, a possibility that Bonewits altered the name of the work to fit with his terminology. He is attempting to track this down. Kelley himself has said to Bonewits that he can't remember which of the two of them said "thealogy" to the other first.
If information could travel faster than ''c'' in one reference frame, [[causality (physics)|causality]] would be violated: in some other reference frames, the information would be received before it had been sent, so the 'cause' could be observed after the 'effect'. Due to special relativity's [[time dilation]], the ratio between an external observer's perceived time and the time perceived by an observer moving closer and closer to the speed of light approaches zero. If something could move faster than light, this ratio would not be a [[real number]]. Such a violation of causality has never been observed.
In [[1976]], [[Valerie Saiving]], ending her "[[Androcentrism]] in Religious Studies" made a much quoted invocation that yearns towards something as yet undefined-
[[Image:light_cone.png|thumb|right|A [[light cone]] defines locations that are in [[causality (physics)|causal contact]] and those that are not.]]
:''it is just possible that the unheard testimony of that half of the human species which has for so long been rendered inarticulate may have something to tell us about the holy which we have not known - something which can finally make us whole.''
To put it another way, information propagates to and from a point from regions defined by a [[light cone]]. The [[interval]] AB in the diagram to the right is '[[time-like]]' (that is, there is a frame of reference in which event A and event B occur at the same ___location in space, separated only by their occurring at different times, and if A precedes B in that frame then A precedes B in all frames: there is no frame of reference in which event A and event B occur simultaneously). Thus, it is hypothetically possible for matter (or information) to travel from A to B, so there can be a causal relationship (with A the 'cause' and B the 'effect').
::(Saiving 1976:197)
===Second(?) usage ===
On the other hand, the interval AC in the diagram to the right is '[[space-like]]' (that is, there is a frame of reference in which event A and event C occur simultaneously, separated only in space; see [[simultaneity]]). However, there are also frames in which A precedes C (as shown) or in which C precedes A. Barring some way of travelling [[faster than light]], it is not possible for any matter (or information) to travel from A to C or from C to A. Thus there is no causal connection between A and C.
In "The Changing of the Gods" 1979:96, [[Naomi Goldenberg]] selfconsciously introduces the term as a half whimsical possibility, an inspirational comment, not a prelude to exegesis. She does not go on to define what thealogy might be, other than the implicit femininity of the coinage. This lack was perhaps because at that time the very assertion of a serious feminist analysis of religion was virtually unheard of, and the introduction of the concept was an excitingly powerful, but vague, possibility.
According to the currently prevailing definition, adopted in [[1983]], the speed of light is exactly 299,792,458 metres per second (approximately 3 × 10<sup>8</sup> metres per second, or about thirty [[centimetre|centimetres]] (one [[foot (unit of length)|foot]]) per [[nanosecond]]). The value of <math>c</math> defines the
[[permittivity]] of free space (<math>\epsilon_0</math>) in [[SI]] units as:
:<math> \varepsilon_0 = 10^{7}/4\pi c^2 \quad \mathrm{(in~ A^2\, s^4\, kg^{-1}\, m^{-3}, \, or \, F \, m^{-1})}</math>
The [[permeability]] of free space (<math>\mu_0</math>) is not dependent on <math>c</math> and is defined in [[SI]] units as:
:<math> \mu_0 = 4\,\pi\, 10^{-7} \quad \mathrm{(in~ kg\, m\, s^{-2}\, A^{-2}, \, or \, N \, A^{-2})}</math>.
These constants appear in [[Maxwell's equations]], which describe [[electromagnetism]], and are related by:
:<math>c= \frac {1} {\sqrt{\varepsilon_0\mu_0}}</math>
This is not to say that both Goldenberg and Saiving do not both offer extremely solid chunks of thealogy, but they do not give an overview of something to which they were midwives.
[[astronomy|Astronomical]] distances are sometimes measured in [[light year|light years]] (the distance that light would travel in one year, roughly [[1 E15 m|9.46 × 10<sup>12</sup>]] kilometres or about 5.88 × 10<sup>12</sup> miles) especially in popularised texts.
===Bonewits again===
==Communications==
The speed of light is of relevance to [[communications]]. For example, given that the equatorial circumference of the [[Earth]] is 40,075 km and <math>c</math>, the theoretical shortest amount of time for a piece of information to travel half the globe is 0.067 second.
Also in [[1979]], in the first revised edition of "Real Magic," Bonewits defined "thealogy" in his Glossary this way: "Intellectual speculations concerning the nature of the Goddess and Her relations to the world in general and humans in particular; rational explanations of religious doctrines, practices and beliefs, which may or may not bear any connection to any religion as actually conceived and practiced by the majority of its members." While the last clause was his editorializing, the majority of the definition was adapted by removing sexist assumptions from a dictionary then in his library. Also in the same glossary, he defined "theology" and "theoilogy" (spelled correctly this time) with nearly identical words, changing the pronouns appropriately. He has since dropped the use of "theoilogy" in favor of "polytheology," also first published by him in the 1974 "Druid Chronicles."
The actual transit time is longer, in part because the speed of light is slower by about 30% in an [[optical fibre]] and straight lines rarely occur in global communications situations, but also because delays are created when the signal passes through an electronic switch or signal regenerator. A typical <!-- round trip? --> time [[as of 2004]] for an [[Australia]] or [[Japan]] to [[United States|US]] computer-to-computer [[ping]] is 0.18 second. The speed of light additionally affects [[wireless]] communications design.
In [[2003]] he pointed out that "thealogy" is an obvious coinage that may have been invented many times, and that feminist scholars are unlikely to have been familiar with his writings.
The finite speed of light became quite apparent to everybody following the communication of [[Houston]] [[ground control]] and [[Neil Armstrong]] when he [[Apollo 11|became the first man]] to set foot on the [[Moon]]: For every question, Houston had to wait nearly 3 [[second]]s for the answer to arrive, and would have to do so even if the astronauts replied immediately. ''([[:Image:Speed of light from Earth to Moon.gif|See animation]].)''
=== Growing usage by Carol Christ and Ursula King ===
Similarly, instantaneous remote control of an interplanetary spacecraft is impossible, in the sense that the time it takes, for example, for the earth-based controllers to become aware of a problem, plus the time it takes for the spacecraft to receive their response, can be some hours.
[[Carol Christ]] used the term more substantially in "Laughter of Aphrodite" [[1987]].
The speed of light can also be of concern on short distances. In [[supercomputer|supercomputers]], the speed of light imposes a limit on how quickly data can be sent between [[processor]]s. If a processor operates at 1 [[GHz]], a signal can only travel a maximum of 300 mm in a single cycle. Processors must therefore be placed close to each other to minimise communication latencies. If clock frequencies continue to increase, the speed of light will eventually become a limiting factor for the internal design of single [[integrated circuit|chips]].
In [[1989]] [[Ursula King]] notes its growing usage as a fundamental departure from traditional male-oriented theology, characterised by its privileging of symbols over rational explanation. She chronicles sympathetically that-
==Physics==
===Constant velocity from all reference frames===
It is important to realise that the speed of light is not a "[[speed limit]]" in the conventional sense. An observer chasing a beam of light will measure it moving away from him at the same speed as a stationary observer. This leads to some unusual consequences for velocities.
:''most writing on the Goddess, when not historical, is either inspirational or devotional, and a systematically ordered body of thought, even with reference to symbols, is only slowly coming into existence.''
Most individuals are accustomed to the addition rule of velocities: if two cars approach each other from opposite directions, each travelling at a speed of 50 [[kilometres per hour]] (31 [[miles per hour]]), one expects that each car will perceive the other as approaching at a combined speed of 50 + 50 = 100 km/h (62 mph) to a very high degree of accuracy.
::(1989:126-127)
== Further expansion of thealogy by Starr* Saffa ==
At velocities at or approaching the speed of light, however, it becomes clear from experimental results that this rule does not apply. Two spaceships approaching each other, each travelling at 90% the speed of light relative to some third observer between them, do not perceive each other as approaching at 90% + 90% = 180% the speed of light; instead they each perceive the other as approaching at slightly less than 99.5% the speed of light.
Tahirih Thealogy
This last result is given by the [[Albert Einstein|Einstein]] velocity addition formula:
The basic Definition of TheAlogy as opposed to Theology means viewing the world incorporating the Female lens which to a great extent in the past has been omitted in Theology.
: <math>u = {v + w \over 1 + v w / c^2} \,\!</math>
Tahirih TheAlogy is religion beyond religion, politics beyond politics, and spiritual feminism beyond feminism in that it recognizes the Cosmic Christ Spirit in every individual and sets out the pattern of balance for the Sixth Cycle of humanity based on magnetic attraction vs. force and patriarchal constructs.
where ''v'' and ''w'' are the speeds of the spaceships as observed by the third observer, and ''u'' is the speed of either space ship as observed by the other.
During the later part of 2004 Starr* Saffa introduced Tahirih Thealogy and the Tahirih Path in her book entitled “Tahirih Thealogy: Female Christ Spirit of the Age” based on the figure of the 19th Century Iranian born Prophet-Poetess Tahirih who was also known as Qurratu’l-ayn, and the return of Fatima.
Contrary to one's usual intuitions, regardless of the speed at which one observer is moving relative to another observer, both will ''measure'' the speed of an incoming light beam as the same constant value, the speed of light.
Tahirih taught that inner knowledge is trumps and Starr* Saffa says Tahirih TheAlogy has the potential to unite East and West where everyone can be living Tahirih’s in this day through the continuous flow of Spirit.
The above equation was derived by [[Albert Einstein]] from his theory of [[special relativity]], which takes the [[principle of relativity]] as a main premise. This principle (originally proposed by [[Galileo Galilei]]) requires physical laws to act in the same way in all [[reference frame]]s. As [[Maxwell's equations]] directly give a speed of light, it should be the same for every observer—a consequence which sounded obviously wrong to the [[19th century]] physicists, who assumed that the speed of light given by Maxwell's theory is valid relative to the [[luminiferous aether]]. But the [[Michelson-Morley experiment]], arguably the most famous and useful failed experiment in the history of physics, could not find this aether, suggesting instead that the speed of light ''is'' constant in all frames of reference.
== Definition by Charlotte Caron ==
Although it is uncertain whether Einstein knew the results of the Michelson-Morley experiment, he took the speed of light being constant as a given fact, understood it as reaffirming Galilei's principle of relativity, and deduced the consequences, now known as the theory of [[special relativity]] which includes the counter-intuitive addition formula above.
In [[1993]] Charlotte Caron's definition of thealogy as "reflection on the divine in feminine and feminist terms" appeared in "To Make and Make Again" (quoted from Russell & Clarkson 1996). By this time the concept had gained considerable (though conventionally marginal) status, broadly analogous to Ruether's view of radical feminist theology as opposed to reformist [[feminist theology]].
===Interaction with transparent materials===
[[Image:PrismAndLight.jpg|right|thumb|300px|The [[refractive index]] of a material indicates how much slower the speed of light is in that medium than in a vacuum. The slower speed of light in materials can cause [[refraction]], as demonstrated by this [[prism (optics)|prism]] (in the case of a prism splitting white light into a [[visible spectrum|spectrum]] of colours, the refraction is known as [[dispersion (optics)|dispersion]]).]]
=== Melissa Raphael's view ===
In passing through materials, light is slowed to less than ''c'' by the ratio called the [[refractive index]] of the material. The speed of light in [[air]] is only slightly less than <math>c</math>. Denser media, such as [[water]] and [[glass]], can slow light much more, to fractions such as 3/4 and 2/3 of ''c''. This reduction in speed is also responsible for bending of light at an interface between two materials with different indices, a phenomenon known as [[refraction]].
In [[1997]] [[Melissa Raphael]] wrote "Thealogy & Embodiment" which put the usage firmly on the map, and which she sustained in her subsequent "Thealogy: Discourse on the Goddess" ([[1999]]?). Together with Carol Christ's "Rebirth of the Goddess" 1997 Raphael's work provides a start for the "systematically ordered body of thought" King found lacking in 1989.
Since the speed of light in a material depends on the refractive index, and the refractive index depends on the frequency of the light, light at different frequencies travels at different speeds through the same material. This can cause distortion of electromagnetic waves that consist of multiple frequencies, called [[dispersion]].
== Three interpretations of thealogy ==
Note that the speed of light referred to is the '''observed or measured speed in some medium''' and not the true speed of light (as observed in vacuum). On the microscopic scale, considering electromagnetic radiation to be like a particle, refraction is caused by continual absorption and re-emission of the [[photon]]s that compose the light by the atoms or molecules through which it is passing. In some sense, the light itself travels only through the vacuum existing between these atoms, and is impeded by the atoms. The process of absorption and re-emission itself takes time thereby creating the impression that the light itself has undergone delay (i.e. loss of speed) between entry and exit from the medium in question. It may be noted, that once the light has emerged from the medium it changes back to its original speed and this is ''without gaining'' any energy. This can mean only one thing - that the light's speed itself was never altered in the first place. Alternatively, considering electromagnetic radiation to be like a wave, the charges of each atom (primarily the [[electron]]s) [[interference|interfere]] with the electric and magnetic fields of the radiation, slowing its progress.
There are perhaps three distinct interpretations of thealogy, and they are evident in the briefing above.
==="Faster-than-light" observations and experiments===
*Christ, King and Raphael focus thealogy specifically on [[Goddess]] spirituality.
Recent experimental evidence shows that it is possible for the [[group velocity]] of light to exceed ''c''. One experiment made the group velocity of [[laser]] beams travel for extremely short distances through [[caesium]] atoms at 300 times ''c''. However, it is not possible to use this technique to transfer [[information]] faster than ''c'': the velocity of information transfer depends on the [[front velocity]] (the speed at which the first rise of a pulse above zero moves forward) and the product of the group velocity and the front velocity is equal to the square of the normal speed of light in the material.
*Caron defines a broader field of a female worldview of the [[sacred]].
*Goldenberg's neologism as a political stance that marks the [[androcentrism]] of historical [[theology]] permeates the other two and raises its own issues.
=== Thealogy as Goddess spirituality ===
Exceeding the group velocity of light in this manner is comparable to exceeding the speed of sound by arranging people in a distantly spaced line, and asking them all to shout "I'm here!", one after another with short intervals, each one timing it by looking at their own wristwatch so they don't have to wait until they hear the previous person shouting.
Taking the Goddess variant first, and it seems the commonest to the point where thealogy is typically assumed to be purely Goddess based, a linguistic derivation from the Greek "thea"
The speed of light may also appear to be exceeded in some phenomena involving [[evanescent waves]], such as [[quantum tunneling|tunnelling]]. Experiments indicate that the [[phase velocity]] of evanescent waves may exceed ''c''; however, it would appear that neither the group velocity nor the front velocity exceed ''c'', so, again, it is not possible for information to be transmitted faster than ''c''.
(goddess). Goddess systematics inevitably face the question of "god in a skirt" or not, a subtly [[sexism|sexist]] tag that nonetheless carries a genuine issue. This can be viewed as sexist because "in a skirt" defines a subject norm as altered, trivialised, and definitely derivative, much as some have considered the female to have been historically defined in relation to the male. Thealogy specifically aims to counter what its proponents perceive as the massive [[dualism|dualistic]] sexism in the field of religion, by asserting a female [[worldview]] that is not merely reformist or derivative, so its proponents would see this quip as especially destructive.
=== Broad interpretation of thealogy (Caron) ===
In some [[interpretations of quantum mechanics]], [[quantum mechanics|quantum]] effects may be transmitted at speeds greater than ''c'' (indeed, [[action at a distance (physics)|action at a distance]] has long been perceived as a problem with quantum mechanics: see [[EPR paradox]]). For example, the [[quantum state]]s of two particles can be [[quantum entanglement|entangled]], so the state of one particle fixes the state of the other particle (say, one must have [[spin (physics)|spin]] +½ and the other must have spin −½). Until the particles are observed, they exist in a [[superposition]] of two quantum states, (+½, −½) and (−½, +½). If the particles are separated and one of them is observed to determine its quantum state then the quantum state of the second particle is determined automatically. If, as in some interpretations of quantum mechanics, one presumes that the information about the quantum state is local to one particle, then one must conclude that second particle takes up its quantum state instantaneously, as soon as the first observation is carried out. However, it is impossible to control which quantum state the first particle will take on when it is observed, so no information can be transmitted in this manner. The laws of physics also appear to prevent information from being transferred through more clever ways and this has led to the formulation of rules such as the [[no-cloning theorem]].
Caron's definition "Reflection on the divine in feminine and feminist terms" holds a caution for feminist theologians and thealogians alike that the female sacred extends beyond the feminist agenda. Often theology or feminist thealogy writes as if the Goddess is a feminist discovery. The "womenspirit" Goddess is a highly selected deity who for thealogians such as Christ has nothing to do with goddess practices such as violent sacrifice, or validating a male conqueror. However, this can be seen to be as inauthentic as the habit of some Christians of disowning the [[Inquisition]] as "not done by real Christians" (see the "[[no true Scotsman]]" [[logical fallacy]]).
So-called [[superluminal motion]] is also seen in certain astronomical objects, such as the [[jet]]s of [[radio galaxy|radio galaxies]] and [[quasar]]s. However, these jets are not actually moving at speeds in excess of the speed of light: the apparent superluminal motion is a [[projection]] effect caused by objects moving near the speed of light and at a small [[angle]] to the line of sight.
Nor is it a matter only of past history: many members of a huge international organisation like the [[Fellowship of Isis]] would not identify as feminist, nor would a great many [[Pagan]]s. Outside the goddessing of western [[New religious movement|NRMs]] thealogy can recognise and give due respect to the world millions in village and tribal religions who look to goddesses in ways that may or may
Although it may sound paradoxical, it is possible for [[shock wave|shock waves]] to be formed with electromagnetic radiation. As a charged particle travels through an [[insulator|insulating]] medium, it disrupts the local electromagnetic field in the medium. Electrons in the atoms of the medium will be displaced and [[polarization|polarised]] by the passing field of the charged particle, and photons are emitted as the electrons in the medium restore themselves to equilibrium after the disruption has passed. (In a [[conductor (material)|conductor]], the disruption can be restored without emitting a photon.) In normal circumstances, these photons destructively interfere with each other and no radiation is detected. However, if the disruption travels faster than the photons themselves travel, the photons constructively interfere and intensify the observed radiation. The result (analogous to a [[sonic boom]]) is known as [[Cherenkov radiation]].
not be feminist, and Caron's definition allows thealogy to be this widely inclusive.
This broader view accords well with the kind of fluid systematics profiled by [[Cynthia Eller]] when she reports her respondent [[Margaret Keane]] as saying:
The ability to communicate or travel [[faster-than-light]] is a popular topic in [[science fiction]]. Particles that travel faster than light, dubbed [[tachyon]]s, have been proposed by [[particle physics|particle physicists]] but have yet to be observed.
:''I don't make those kind of distinctions that you hear about, they don't make any sense to me. You can say it's the Great Goddess, and that's the one Goddess, but she's also all of the many goddesses, and that's true. And she's everywhere. She's immanent in everything, in the sparkle of the sun on the sea, and even in an animistic concept. I think certain objects can embody that force and power. So I worship the Great Goddess, and I'm polytheistic and pantheistic and monotheistic too. And I also have a feeling for nature spirits...''
Some physicists, notably [[Joao Magueijo]] and [[John Moffat]], have proposed that in the past light travelled much faster than the current speed of light. This theory is called [[variable speed of light]] (VSL) and its supporters claim that it has the ability to explain many [[cosmology|cosmological]] puzzles better than its rival, the [[Cosmic inflation|inflation]] model of the [[universe]]. However, it has yet to gain wide acceptance.
::(1993 :132-133)
This broader view has most recently been labelled by [[Michael York]] as "polymorphic thealogy." He also raises the issue of whether thealogy venerates one Goddess or many, which some thealogicians consider a non-question since it arises from a monotheist worldview that they do not hold.
===Light-slowing experiments===
[[Image:Epcot rainbow.jpg|right|thumb|[[Refraction|Refractive]] phenomena, such as this [[rainbow]], are due to the slower speed of light in a medium (water, in this case).]]
In a sense, any light travelling through a medium other than a vacuum travels below <math>c</math> as a result of refraction. However, certain materials have an exceptionally high refractive index: in particular, the [[optical density]] of a [[Bose-Einstein condensate]] can be very high. In [[1999]], a team of scientists led by [[Lene Hau]] were able to slow the speed of a [[light]] [[beam]] to about 17 metres per second, and, in [[2001]], they were able to momentarily stop a beam.
However Caron's definition falls short of explicitly allowing for male positions in thealogy.
In [[2003]], [[Mikhail Lukin]], with scientists at [[Harvard University]] and the [[Lebedev Physical Institute|Lebedev Institute]] in [[Moscow]], succeeded in completely halting light by directing it into a mass of hot [[rubidium]] gas, the atoms of which, in Lukin's words, behaved "like tiny mirrors", due to an interference pattern in two "control" beams.
=== A challenge to androcentrism ===
==History==
Until relatively recent times, the speed of light was largely a matter of conjecture. [[Empedocles]] maintained that light was something in motion,
and therefore there had to be some time elapsed in travelling. [[Aristotle]] said that, on the contrary, "light is due to the presence of something, but it is not a movement". Furthermore, if light had a finite speed, it would have to be very great; Aristotle asserted "the strain upon our powers of belief is too great" to believe this.
The third interpretation of thealogy as an assertion of female sacred worldviews is clearly political. The notes above touch on how this usage aims to counter the deeply established dualistic relegation of female as derivative, making the male the norm: as [[Mary Daly]] put it "If God is male, then the male is God."
One of the ancient theories of vision is that light is emitted from the eye,
instead of being reflected into the eye from another source. On this theory,
[[Heron of Alexandria]] advanced the argument that the speed of light must be [[infinite]], since distant objects such as stars appear immediately when one opens one's eyes.
Thealogy has been criticised as [[essentialism|essentialist]] by [[queer theory|queer theorists]] and others.
===Medieval and early modern theories===
The [[Islam]]ic [[philosopher]]s [[Avicenna]] and [[Alhazen]] believed that light has a finite speed, although most philosophers agreed with Aristotle on this point. The [[Aryan]] school of philosophy in ancient India also held the speed of light to be finite. The [[14th century]] philosopher [[Sayana]] wrote the following comment on verse 1.50 of the [[Rig Veda]]:
:"Thus it is remembered: [O Sun] you who traverse 2202 yojanas in half a nimesa."
According to some, this refers to the speed of light. It is not known exactly how long a yojana and a nimesa is, but this value is possibly accurate to within 1% (Kak, 1998), though by adopting other possible values of these units the accuracy of the statement can be reduced to a factor of 4.
To a thealogian it is important to explore the female worldview (not only but notably of the sacred) and not be compelled to take off female spectacles when looking at themes beyond female [[psychobiology]]. A speaker may choose to adopt a kind of gender neutral stance insofar as she can, or she may try to empathise with a male worldview, and a male speaker vice versa.
[[Johannes Kepler]] believed that the speed of light is infinite since empty space presents no obstacle to it. [[Francis Bacon]] argued that the speed of light is not necessarily infinite, since something can travel too fast to be perceived. [[René Descartes]] argued that if the speed of light were finite, the [[Sun]], [[Earth]], and [[Moon]] would be noticeably out of alignment during a [[lunar eclipse]]. Since such misalignment had not been observed, Descartes concluded the speed of light is infinite. In fact, Descartes was convinced that if the speed of light were finite, his whole system of philosophy would be demolished.
== Linguistic twiddling ==
===Measurement of the speed of light===
[[Isaac Beeckman]], a friend of Descartes, proposed an experiment (1629) in which one would observe the flash of a [[cannon]] reflecting off a [[mirror]] about one mile away. [[Galileo Galilei|Galileo]] proposed an experiment (1638), with an apparent claim to have performed it some years earlier, to measure the speed of light by observing the delay between uncovering a [[lantern]] and its perception some distance away. Descartes criticised this experiment as superfluous, in that the observation of eclipses, which had more power to detect a finite speed, gave a negative result. This experiment was carried out by the Accademia del Cimento of Florence in 1667, with the lanterns separated by about one mile. No delay was observed. [[Robert Hooke]] explained the negative results as Galileo had: by pointing out that such observations did not establish the infinite speed of light, but only that the speed must be very great.
Many scholars find the term "thealogy" exasperating, a linguistic twiddling, including some feminist theologians. But the position of women operating within the male worldview of theology, as in most of [[feminist theology]], is more marginal than in the general run of professional occupations these days. The rigidly entrenched sexism in the contemporary academy perceived by some thealogs recalls situations of general Women's Liberation in 1972, rather than society 30 years later (see recent research studies Ofsted UK).
The first quantitative estimate of the speed of light was made in [[1676]] by [[Ole Rømer]], who was studying the [[motion]]s of [[Jupiter (planet)|Jupiter]]'s satellite [[Io (moon)|Io]] with a [[telescope]]. It is possible to time the [[revolution]] of Io because it is entering/exiting Jupiter's shadow at regular [[interval (time)|interval]]s. Rømer observed that Io revolved around Jupiter once every 42.5 [[hour]]s when [[Earth]] was closest to Jupiter. He also observed that, as Earth and Jupiter moved apart, Io's exit from the shadow would begin progressively later than predicted. It was clear that these exit "signals" took longer to reach Earth, as Earth and Jupiter moved further apart, as a result of the extra time it took for light to cross the extra distance between the planets, which had accumulated in the interval between one signal and the next. Similarly, about half a year later, Io's entries into the shadow happened more frequently, as Earth and Jupiter were now drawing closer together. On the basis of his observations, Rømer estimated that it would take light 22 minutes to cross the diameter of the orbit of the Earth (that is, twice the [[astronomical unit]]); the modern estimate is closer to 16 minutes and 40 seconds.
==See also==
Around the same time, the astronomical unit was estimated to be about 140 million kilometres. The astronomical unit and Rømer's time estimate were combined by [[Christiaan Huygens]], who estimated the speed of light to be 1000 Earth diameters per minute. This is about 220,000 kilometres per second (136,000 miles per second), well below the currently accepted value, but still very much faster than any physical phenomenon then known.
*[[God and gender]]
*[[feminist theology]]
*[[goddess]]
*[[goddess worship]]
==References==
[[Isaac Newton]] also accepted the finite speed. In his book "[[Opticks]]" he, in fact, reports the more accurate value of 16 minutes per diameter, which it seems he inferred for himself (whether from Rømer's data, or otherwise, is not known). The same effect was subsequently observed by Rømer for a "spot" rotating with the surface of Jupiter. And later observations also showed the effect with the three other Galilean moons, where it was more difficult to observe, thus laying to rest some further objections that had been raised.
* Isaac Bonewits "The Second Epistle of Isaac" in "the Druid Chronicles (Evolved)" Berkeley Drunemeton Press, 1974.
*Isaac Bonewits "Real Magic" Creative Arts Book Co., 1979
*Charlotte Caron "To Make and Make Again: Feminist Ritual Thealogy" NY Crossroad 1993
*Carol Christ "Rebirth of the Goddess:Finding meaning in feminist spirituality" Routledge 1997
*Cynthia Eller "Living in the Lap of the Goddess: The Feminist Spirituality Movement in America" Crossroad 1993
*Naomi Goldenberg "The Changing of the Gods" 1979
*Ursula King "Women and Spirituality" Macmillan 1989
*Melissa Raphael "Thealogy & Embodiment" 1997 Sheffield Academic Press
*Melissa Raphael "Introducing Thealogy: Discourse on the Goddess" 1999 Sheffield Academic Press
*Letty M. Russell & J Shannon Clarkson "Dictionary of Feminist Theologies" Mowbray 1996.
*Starr* Saffa "Tahirih Thealogy: Female Christ Spirit of the Age" OzForUs Publishing 2004; Zeus-publications 2005.
*Valerie Saiving "Androcentrism in Religious Studies" in Journal of Religion 56:1976:177-97
[[Category:Theology]]
Even if, by these observations, the finite speed of light may not have been established to everyone's satisfaction (notably [[Giovanni Domenico Cassini|Jean-Dominique Cassini]]'s), after the observations of [[James Bradley]] ([[1728]]), the hypothesis of infinite speed was considered discredited. Bradley deduced that starlight falling on the Earth should appear to come from a slight angle, which could be calculated by comparing the speed of the Earth in its orbit to the speed of light. This "[[aberration of light]]", as it is called, was observed to be about 1/200 of a degree. Bradley calculated the speed of light as about 185,000 miles per second (298,000 kilometres per second). This is only slightly less than the currently accepted value. The aberration effect has been studied extensively over the succeeding centuries, notably by [[Friedrich Georg Wilhelm Struve]] and [[Magnus Nyren]].
[[Image:Speed_of_light_(Fizeau).PNG|thumb|right| Diagram of the [[Fizeau-Foucault apparatus]].]]
The first successful measurement of the speed of light using an earthbound apparatus was carried out by [[Hippolyte Fizeau]] in [[1849]]. Fizeau's experiment was conceptually similar to those proposed by Beeckman and Galileo. A beam of light was directed at a mirror several thousand metres away. On the way from the source to the mirror, the beam passed through a rotating cog wheel. At a certain rate of rotation, the beam could pass through one gap on the way out and another on the way back. But at slightly higher or lower rates, the beam would strike a tooth and not pass through the wheel. Knowing the distance to the mirror, the number of teeth on the wheel, and the rate of rotation, the speed of light could be calculated. Fizeau reported the speed of light as 313,000 kilometres per second. Fizeau's method was later refined by [[Marie Alfred Cornu]] ([[1872]]) and [[Joseph Perrotin]] ([[1900]]).
[[Leon Foucault]] improved on Fizeau's method by replacing the cogwheel with a rotating mirror. Foucault's estimate, published in [[1862]], was 298,000 kilometres per second. Foucault's method was also used by [[Simon Newcomb]] and [[Albert A. Michelson]]. Michelson began his lengthy career by replicating and improving on Foucault's method.
In [[1926]], Michelson used rotating mirrors to measure the time it took light to make a round trip from [[Mount Wilson (California)|Mount Wilson]] to [[Mount San Antonio]] in [[California]]. The precise measurements yielded a speed of 186,285 miles per second (299,796 kilometres per second).
===Relativity===
Due to the works of [[James Clerk Maxwell]], it was known that the speed of electromagnetic radiation was a constant defined by the electromagnetic properties of the vacuum ([[permittivity]] and [[permeability (electromagnetism)|permeability]]).
[[image:interferometer.png|thumb|right|A schematic representation of a [[Albert Michelson|Michelson]] [[interferometer]], as used for the Michelson-Morley experiment.]]
In [[1887]], the physicists [[Albert Michelson]] and [[Edward Morley]] performed the influential [[Michelson-Morley experiment]] to measure the speed of light relative to the motion of the earth, the goal being to measure the velocity of the [[Earth]] through the "[[luminiferous aether]]", the medium that was then thought to be necessary for the transmission of light. As shown in the diagram of a Michelson [[interferometer]], a [[beam splitter|half-silvered mirror]] was used to split a beam of [[monochromatic]] light into two beams travelling at [[right angle]]s to one another. After leaving the splitter, each beam was reflected back and forth between [[mirror]]s several times (the same number for each beam to give a long but equal path length; the actual Michelson-Morley experiment used more [[mirror]]s than shown) then recombined to produce a pattern of constructive and destructive [[interference]]. Any slight change in speed of light along each arm of the interferometer (due to the fact that the apparatus was moving with the Earth through the proposed "aether") would change the amount of time that the beam spent in transit, which would then be observed as a change in the pattern of interference. In the event, the experiment gave a [[null result]].
[[Ernst Mach]] was among the first physicists to suggest that the experiment actually amounted to a disproof of the ''aether'' theory. Developments in theoretical physics had already begun to provide an alternate theory, [[Fitzgerald-Lorentz contraction]], which explained the null result of the experiment.
It is uncertain whether [[Albert Einstein]] knew the results of the Michelson-Morley experiment, but the null result of the experiment greatly assisted the acceptance of his [[theory of relativity]]. Einstein's theory did not require an aether but was entirely consistent with the null result of the experiment: the ''aether'' did not exist and the speed of light was the same in each direction. The constant speed of light is one of the fundamental Postulates (together with [[causality (physics)|causality]] and the [[equivalence of inertial frames]]) of special relativity.
==See also==
*[[Fizeau-Foucault apparatus]]
* [[variable speed of light]]
== References ==
=== Historical references ===
* Ole Rømer. "Démonstration touchant le mouvement de la lumière", ''Journal des Sçavans'', 7 Décembre 1676, pp. 223-236. Translated as "A Demonstration concerning the Motion of Light", ''Philosophical Transactions of the [[Royal Society]]'' no. 136, pp. 893-894; June 25, 1677. ''(Rømer's 1676 paper, in English and French, as bitmap images: [http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Roemer-1677/Roemer-1677.html], and in French as plain text: [http://astro.campus.ecp.fr/histoire/roemer.html])''
* Edmund Halley. "Monsieur Cassini, his New and Exact Tables for the Eclipses of the First Satellite of Jupiter, reduced to the Julian Stile and Meridian of London", ''Philosophical Transactions'' XVIII, No. 214, pp 237–256, Nov.–Dec., 1694.
* H.L. Fizeau. "Sur une experience relative a la vitesse de propogation de la lumiere", ''Comptes Rendus'' 29, 90–92, 132, 1849.
* J.L. Foucault. "Determination experimentale de la vitesse de la lumiere: parallaxe du Soleil", ''Comptes Rendus'' 55, 501–503, 792–796, 1862.
* A.A. Michelson. "Experimental Determination of the Velocity of Light", ''Proceedings of the American Association for the Advancement of Science'' 27, 71–77, 1878.
* Simon Newcomb. "The Velocity of Light", ''Nature'', pp 29–32, May 13, 1886.
* Joseph Perrotin. "Sur la vitesse de la lumiere", ''Comptes Rendus'' 131, 731–734, 1900.
* A.A. Michelson, F.G. Pease, and F. Pearson. "Measurement Of The Velocity Of Light In A Partial Vacuum", ''Astrophysical Journal'' 82, 26–61, 1935.
=== Modern references ===
* John David Jackson. ''Classical electrodynamics''. John Wiley & Sons, 2nd edition, 1975; 3rd edition, 1998. ISBN 047130932X
* Subhash Kak. The Speed of Light and Purāṇic Cosmology. In T.R.N. Rao and S. Kak, ''Computing Science in Ancient India,'' pages 80–90. USL Press, Lafayette, 1998. Available as [http://uk.arxiv.org/abs/physics/9804020 e-print physics/9804020] on the [[arXiv]].
* R.J. MacKay and R.W. Oldford. "Scientific Method, Statistical Method and the Speed of Light", ''Statistical Science'' 15(3):254–278, 2000. ''(Also available on line: [http://www.stats.uwaterloo.ca/~rwoldfor/papers/sci-method/paperrev])''
==External links ==
*[http://physics.nist.gov/cgi-bin/cuu/Value?c speed of light in vacuum] ''(at [[NIST]])''
*[http://www.ldolphin.org/chistory.html A Brief History of ''c'']
*[http://www.itl.nist.gov/div898/bayesian/datagall/michelso.htm Data Gallery: Michelson Speed of Light (Univariate Location Estimation)] ''(download data gathered by [[Albert Abraham Michelson|A.A. Michelson]])''
*[http://physicsweb.org/article/news/7/12/5 Switching light on and off] ''(news article on stopping light)''
*[http://news.bbc.co.uk/hi/english/sci/tech/newsid_841000/841690.stm Beam smashes light barrier] ''(news article on group velocity experiment)''
*[http://www.netspace.net.au/~gregegan/APPLETS/20/20.html Subluminal] ''(Java applet demonstrating group velocity information limits)''
*[http://www.ertin.com/sloan_on_speed_of_light.html Light discussion on adding velocities]
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