Einstein's Theory To Go Beta Testing

pinqkandi writes: "This article over at CNN looks into the relativity of Einstein's theory of relativity (pun intended) as equipment becomes more and more precise. Soon atomic clocks will be placed in the International Space Station to analyze the accuracy of Einstein's theories. One of the lead researchers says that if Einstein's theory is not right, it will only need minor adjustments to account for changes in space-time, due to its deadly accurate precision."

Zero gravity?

[tdemark]

Maybe it's just the way the guy was quoted in the article, but if they need to test in a "zero gravity" environment, how would the ISS be applicable?

I'd consider it a "weightless" environment, but not "zero gravity".

- Tony

"Beta testing"?

[PhysicsGenius]

Even as a joke this makes no sense. Relativity was alpha tested in the 1913 (IIRC) eclipse and has been tested very very thoroughly since then. This is just another fine-grained test.

What is the CNN article saying??

[BongoBonga]

The CNN article is not very clear as to what it says. This comes from the fact that There are two different theorys of relativity.

1 The special theory
2 the General theory.

The special theory concerns what happens to the laws of physics as a person is traveling at a constant velocity, whereas the general theory is concerned with bodys that are accelerating ( In general relativity acceleration and gravity are equivalent).

So since the ISS is in orbit it experences an outwards accerleration( the same as one experences as one goes round a corner fast in a car.) In space there is gravity on the ISS but it is very little. This means that the ISS will experence a slight change in the ticking rate that is recorded. But this is explained by the general theory of relativity and not the special theory.

Re:What's wrong with the older proofs?

[danro]

Hasn't this been proved already? What's wrong with those older proofs?

You can't prove anything in physics, you can try to disprove something and fail, and thus you may have reason to believe that the theory was correct.
But there is always a posibility that your theory may be disproved later. (Which doesn't mean the theory is rendered useless. Newton's mechanics for example, stood for a very long time, until they were replaced by the theories of relativity. But they are still used, because in most "normal" conditions they work good enought, and the math is easier to work with.)

Re:GPS Satelites know this !

[fisman]

And also from one of the links:

For GPS satellites, GR predicts that the atomic clocks at GPS orbital altitudes will tick faster by about 45,900 ns/day because they are in a weaker gravitational field than atomic clocks on Earth's surface. Special Relativity (SR) predicts that atomic clocks moving at GPS orbital speeds will tick slower by about 7,200 ns/day than stationary ground clocks. Rather than have clocks with such large rate differences, the satellite clocks are reset in rate before launch to compensate for these predicted effects. In practice, simply changing the international definition of the number of atomic transitions that constitute a one-second interval accomplishes this goal. Therefore, we observe the clocks running at their offset rates before launch. Then we observe the clocks running after launch and compare their rates with the predictions of relativity, both GR and SR combined. If the predictions are right, we should see the clocks run again at nearly the same rates as ground clocks, despite using an offset definition for the length of one second.

We note that this post-launch rate comparison is independent of frame or observer considerations. Since the ground tracks repeat day after day, the distance from satellite to ground remains essentially unchanged. Yet, any rate difference between satellite and ground clocks continues to build a larger and larger time reading difference as the days go by. Therefore, no confusion can arise due to the satellite clock being located some distance away from the ground clock when we compare their time readings. One only needs to wait long enough and the time difference due to a rate discrepancy will eventually exceed any imaginable error source or ambiguity in such comparisons.

This in the other hand sound pretty scientific and conclusive to me ...

Re:it's truly relative

[Jerf]

Of course, you can only accept the parent of this post by tossing all logic out the window.

Time most assuredly does exist. I am perceiving time, therefore I am perceiving something. Whatever this something is, I define as "time". Viola.

You may think you can wiggle out of this by claiming that what I'm perceiving is an illusion, but no such luck; I define your claimed illusion as "time" (without conceding your illusion point.) It doesn't matter how you try to do this, I can always go one meta-level higher. You can't win without throwing out logic, at which point I declare moral victory anyhow.

The parent is really a hidden instance of "overgeneralization".

• "I know of this thing 'x'", where "x" is "time" today (no pun intended).
• "This thing 'x' does not exist."
• "Therefore, no thing thought of under the word 'x' exists."

I hope I don't need to spell out why that's fallacious logic? (Hint: Just because you don't understand something doesn't affect the universe. Hint 2: You can't go "Newtonian gravity is incorrect. Therefore, there is no such thing as gravity." It's the same form, honest.)

Of course the universe cannot be totally explained and there's a lot of mystery out there. Indeed, that's exactly why making up fake mystery is a waste of time! There's plenty to exercise your sense of wonder on or whatever other reason your subconcious is rebelling at this message for; why make up fake stuff like this? You need all the help you can get; throwing out logic pretty much leaves you adrift, with no clue. You wanna be that way, fine, no skin off my nose, but don't suffer under the illusion that you're any more 'enlightened' then me.

Re:GPS does velocity already!!!!!!

[DarkState]

A detail that I left out of my previous post is that Kostelecky and co-workers have developed a framework describing a very general set of extensions to the standard model which violate Lorentz invariance. You can find out more about this set of extensions at his website and in the papers referenced there. His framework (which I don't understand in the detail which I should) includes a set of parameters (whose values must be determined by experiment) which are Lorentz invariant in some underlying high energy theory but lead to CPT and Lorentz violations in the low energy limit (where the low energy limit includes everything from atomic clocks to the highest energy accelerators).

It turns out, however, that a standard atomic clock such as those used in the GPS satellites is not sensitive to these effects. In the measurements Kostelecky is talking about and the measurements we have done on the ground, one looks not at the standard clock frequency (based on the hyperfine transition) but instead at an auxillary frequency (a Zeeman transition) which has a first order magnetic field dependence. This frequency is sensitive (in leading order at low magnetic fields ) to the effects Kostelecky's framework predicts.
Therefore, one needs to operate an atomic clock in a slightly unusual way to search for these effects. In the hydrogen maser measurements we have performed (the Phys. Rev. D paper I mentioned) we measure the standard clock frequency while "tickling" the Zeeman frequency and record the shifts. A similar technique is being proposed in space. I wouldn't think that such a technique would be realistic on the functioning GPS satellites.