Violating relativity by breaking equivalence

[n2doc]

By Matt Ford

One of the tenets of Einstein's theory of general relativity is that an observer, carrying out local measurements, cannot determine if they are being accelerated in the absence of gravitational fields or stationary but in the vicinity of a large gravitational field. That is to say, if you are in a locked laboratory with no way to examine the outside, you could not tell if you were sitting on a beach on Earth, or in the back end of a spaceship speeding up at a rate of 32.2 feet per second per second. Some new thought experiments, however, suggest that the "simple" act of measuring temperature may throw this truism into turmoil.

There are a few caveats. First, the gravitational field cannot be so strong, or the reference frame so large, that tidal forces are present (a fancy way of saying that the gravitational field does not change over the range of the observable space). Second, you can only make a local measurement.

Einstein proposed the equivalence principle in 1907, a full nine years before his publication of general relativity. The idea, however, guided the development of general relativity. When combined with Einstein's theory of special relativity, it gave rise to the prediction that clocks will run at different speeds in gravitational fields with differing strengths, and that light would be bent by gravitational fields.

Numerous experiments, measuring all types of phenomena, have proven that the equivalence principle holds. However, a new thought experiment published in a recent version of Physical Review Letters demonstrates that, depending on how you measure temperature, a scientist in the sealed laboratory could tell where she is. On the surface, this result would seem to suggest that the equivalence principle it not valid under all conditions, but there is a wrinkle—the researchers here suggest making a local quantum mechanical measurement. The fact that quantum mechanics is an inherently non-local phenomenon may provide a way of cheating the prerequisites that Einstein put on his equivalence principle.

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http://arstechnica.com/science/news/2011/08/violating-relativity-by-breaking-equivalence.ars

[phantom power]

1. You break it, you bought it.

[drm604]

2. Obviously this is over my head.

My first thought is that a temperature difference can be caused by all kinds of things, so how can you use it to make this differentiation? :shrug:

[dtexdem]

3. But if relativity is violated -- does that mean that inlaws are outlawed?

;-)

But thanks for the post and the link.

[DetlefK]

4. So, the curved spacetime of a Schwarzschild-metric has a different vacuum than the flat spacetime of

a Minkowski-metric. Your scales are shifted, and that's why you measure different temperatures.

Sweet!