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The bucket experiment is profoundly important, but it does not prove absolute space. |
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([[User:William M. Connolley|William M. Connolley]] 21:42, 18 Oct 2004 (UTC)) I think the variant is due to [[Ernst Mach]]. But OTOH the variant I'm used to is an otherwise empty universe featuring two spheres joined together by a rope. If you measure the tension in the rope you can find out if they are spinning. [[Mach's principle]] says that there is no tension. I think.
so... is this true then or what? does this prove there is an absolute frame of reference? i have been wondering this since i was like 12 so it would be nice to know why nobody ever discusses it... -plasticlax
It appears that rotation is absolute, but translation is still relative. [[User:Pstudier|pstudier]] 08:12, 2004 Apr 1 (UTC)
:Einstein's theory of general relativity does not need the assumption of absolute space. Of course, Einsteins theory of gravity and motion '''does''' need to provide a mechanism that is telling matter whether it is accelerating or not, the bucket thought experiment proves that.
:According to the theory of general relativity there is a universal inertial field. This universal inertial field is transparant to velocity, so all velocities are indistinguishable, but whenever an object accelerates, there is interaction with the universal inertial field, opposing (but not preventing) the acceleration, hence the formula of proportion: F=ma. In a universe without matter the inertial field would be identical to minkowsky space-time everywhere. But matter deforms the inertial field in its neighbourhood, and wherever the universal inertial field is deformed only limited volumes of space are effectively indistinguishable from minkowski space-time. The part of this deformation of space-time geometry that counts the most is the gravitational [[time dilation]]. When matter moves through deformed space-time geometry, the line of travel is seen to be curved when looked at from a sufficient distance. Unlike electromagnetic interaction, that is mediated by a "carrier" that travels in space, gravitational interaction is mediated by deformation of the very fabric of space-time itself. Deformation of the gravito-inertial field and deformation of the space-time geometry are one and the same thing in the theory of general relativity.
:Rotation is not absolute, but according to general relativity it is exceedingly rare to see significant rotation of local space-time geometry with respect to the universe. Hence rotation measured against the locar space-time geometry and rotation with respect to distant stars are invariably seen to match. General relativity does predict under what (extreme) circumstances significant local rotation of space-time geometry with respect to the Universe will occur.
:When two spaceships are co-accelerating, then their relative velocity is zero. However, when they want to communicate, for example by radio signals, they observe the signals are distorted. Their interaction with space-time affects the signals. It is only when both space-ships are moving inertially that the laws of special relativity apply. When the spaceships are both accelerating they must each take their individual interaction with the universal inertial field into account. --[[User:Cleon Teunissen|Cleon Teunissen]] | [[User talk:Cleon_Teunissen|Talk]] 18:19, 19 Mar 2005 (UTC)
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