How accurate is time dilation equation?

[kalesh]

Hi,

Does anyone know of any experiments done to prove the accurateness of the time dilation equation?:confused:

 

I would like to know if it and the other equations on special relativity are truely accurate or are they approximations till some point just as general relativity is an approximation to special relativity at low speeds?

 

Thanks in advance for any help.

[Jay-qu]

I dont know where you heard "general relativity is an approximation to special relativity at low speeds" Im fairly sure thats false. The second subsumes the first.

 

An experiment was carried out on a binary pulsar (two rotating neutron stars) and it was found that Einsteins theory is accurate to one part in 10^14!

 

Reference: The Emperour's New Mind - Roger Penrose.

 

Hope that helps :confused:

[sanctus]

And I guess you meant to say oneof the following:

1) Newtonian mechanics is an approximation of special relativity at low speeds.

 

2)Locally you can apply special relativity in GR....

[Uclock]

The most famous experiment involving time dilation was probably the one by Hefele and Keating undertaken in October of 1971. The experiment involved the use of atomic clocks. One placed at the United States Naval Observatory another four clocks were placed on scheduled aircraft and flown twice around the world, some heading east and the others heading west.

It was predicted from Einstein’s Relativity that the clocks moving in the easterly direction would gain time compared to the clock at the observatory. It is this experiment that physics uses as proof that time dilation is real. When the raw data was released Dr Kelly said the data was averaged in a biased way in order to claim such high precision while the inventor of the atomic clock, Louis Essen, pointed out the inadequate accuracy of the experiment.

 

Tony

[Jay-qu]

You say that was one of the most famous, but was inconclusive?

 

The experiment has since been re-done and confirmed with more accurate clocks AFAIK.

[Uclock]

Confirmed to what level of accuracy?

[CraigD]

An experiment was carried out on a binary pulsar (two rotating neutron stars) and it was found that Einsteins theory is accurate to one part in 10^14!

I’m unfamiliar with this experiment, and would like to know more.

 

As far as I know, one of the best special relativity validating experiments is from ‘Test of the Second Postulate of Special Relativity in the GeV region’, Physics Letters 12, 260 (1964).” This experiment involved generating neutral pi mesons (pions, [math]\pi^0[/math]), which decay into a muon and a neutrino in well-defined mean time of 2.6*10^-8 s. This makes them good “clocks” that can created with a precise speed close to the speed of light, allowing a straightforward measurement of the distance traveled before they decay. Though this experiments, and later replications of it, verified the time-dilation prediction of Special Relativity, I don’t think they was any where near as precise as 1:10^14.

 

To the best of my knowledge, the 1:10^14 figure is from a General Relativity test done in 2003 by the Cassini probe – the ”Cassini test”.

The most famous experiment involving time dilation was probably the one by Hefele and Keating undertaken in October of 1971.

Straightforward tests of Relativity involving very accurate conventional (“atomic”) clocks on aircraft and spacecraft (the GPS satellite system is a well-known source of such data), have, I think, yielded verification much less precise than either of these previous experiments. Major reasons for this limited precision include that even these very precise clocks are still barely capable of detecting the very small time dilation predicted for the speeds air and spacecraft can reach, and that it’s difficult to separate time dilation due to Special (speed) vs. General (gravity) Relativity in craft near massive bodies such as Earth. Such experiments involve many complicated variations in speed and gravity, requiring complicated, precision-impairing calculations. Some have, IMHO been rightly criticized for claiming more accuracy than their data and analysis methods warranted.

[Uclock]

CraigD

 

As I understand it the cassini test was a measurement of the distortion of spacetime caused by the Sun’s gravitational field which I have no problem with but what experiment has ever been done that involves purely velocity to account for time dilation?

 

Tony

[CraigD]

… what experiment has ever been done that involves purely velocity to account for time dilation?

Experiments such as that described in “Test of the Second Postulate of Special Relativity in the GeV region’, Physics Letters 12, 260 (1964).” (I’m unable to find an online reprint of this article, but excerpts of it can be found in usergroup and forums threads, and in several popular books)

 

Importantly, note that this experiment is performed over only a bit more than a meter distance, in the same gravitational field for both the fast-moving and slow-moving pion – on the Earth’s surface, at CERN.

[Erasmus00]

An experiment was carried out on a binary pulsar (two rotating neutron stars) and it was found that Einsteins theory is accurate to one part in 10^14!

 

I believe this was a test for decaying of the orbit due to gravitational waves? Not time dilation? I could be wrong.

-Will

[Erasmus00]

CraigD

 

As I understand it the cassini test was a measurement of the distortion of spacetime caused by the Sun’s gravitational field which I have no problem with but what experiment has ever been done that involves purely velocity to account for time dilation?

 

Muon decay, both on the Earth and in particle accelerators.

-Will

[Uclock]

Erasmus00

 

Muon decay, both on the Earth and in particle accelerators.

 

Particle accelerators accelerate particles, that is why they are called particle accelerators. Muon decay is caused be high energy cosmic rays impacting air molecules producing pions which decay into muons the point here is they have been accelerated by the impact.

 

Tony

[CraigD]

CraigD

 

As I understand it the cassini test was a measurement of the distortion of spacetime caused by the Sun’s gravitational field which I have no problem with but what experiment has ever been done that involves purely velocity to account for time dilation?

 

Tony

Muon decay, both on the Earth and in particle accelerators.

(Earth’s) surface detection of pions is a good (and I think early) experimental validation of Special Relativity predictions. Because of the natural occurrence of pions, and their decay component muons, and because the Earth’s atmosphere is thick enough that without time dilation, muons would rarely reach its surface, muon decay is an effective “low budget” experiment, though not, I think, a very precise one.

 

Thought I’m unfamiliar with a precise measurement of muon decay conducted in a Earth’s surface lab setting, I wouldn’t be surprised to learn that many have been done. It would take a bigger lab, though. While a pion decays in about a meter, a muon takes about 660 m – big, but, I think, very feasible.

[Erasmus00]

Thought I’m unfamiliar with a precise measurement of muon decay conducted in a Earth’s surface lab setting, I wouldn’t be surprised to learn that many have been done. It would take a bigger lab, though. While a pion decays in about a meter, a muon takes about 660 m – big, but, I think, very feasible.

 

It depends on how fast the muon is going. In experiments just at threshold for muon production, very slow muons will result. As such, they decay much faster than muons produced by high energy cosmic rays. By looking at the muon distribution and comparing to the energy of the beam, you can make a reasonable verification of special relativity. As you mentioned, you can also do this with pions.

-Will

[Erasmus00]

Particle accelerators accelerate particles, that is why they are called particle accelerators. Muon decay is caused be high energy cosmic rays impacting air molecules producing pions which decay into muons the point here is they have been accelerated by the impact.

 

Muon decay is just what happens when a muon decays. How the muon is produced is more or less irrelevant. Muons can be produced in particle accelerators, although with modern particle accelerators (the tevatron, or (soon) the LHC) the energies are much higher than muon threshhold, and so you produce them less often.

-Will

[Uclock]

Hi Will

 

Muon decay is just what happens when a muon decays. How the muon is produced is more or less irrelevant. Muons can be produced in particle accelerators, although with modern particle accelerators (the tevatron, or (soon) the LHC) the energies are much higher than muon threshhold, and so you produce them less often.

 

Will, with all due respect you are missing my point. I am saying that velocity does not account for time dilation, only a force will dilate time such as the force felt when an object is accelerated or held still inside a gravitational field. In both cases, impact by cosmic rays and the use of particle accelerators these particles are accelerated.

Where is the proof that velocity accounts for time dilation?

 

Tony

[Jay-qu]

Hi Will

 

 

 

Will, with all due respect you are missing my point. I am saying that velocity does not account for time dilation, only a force will dilate time such as the force felt when an object is accelerated or held still inside a gravitational field. In both cases, impact by cosmic rays and the use of particle accelerators these particles are accelerated.

Where is the proof that velocity accounts for time dilation?

 

Tony

:)

 

So let me get this straight!

 

A particle only experences time dilation when it is acted on by a force - a force that produces an acceleration, an acceleration that increases velocity..

 

Well it cant be due to the force or the acceleration, because once cruising speed is reached - no acceleration and hence no force - time dilation still occurs!