In article ,
says...

On 14/05/2018 11:16, Jeff Findley wrote:
In article ,
says...

https://en.wikipedia.org/wiki/File:D..._dilation.pngT

Why don't you measure time dilation on the ISS ?
Physicists are claiming that clocks on the ISS would lose 24.6 us/day,
whereas clocks on the GPS are claimed to gain 37 us/day. Since the
clocks are in free fall in both cases this seems highly unlikely to me.

Time dilation happens due to the difference in velocity between two
points. It absolutely happens. GPS takes that into account due to the
precise timings required (i.e. since it's used on earth, the time
reference is adjusted such that receivers on the earth get the correct
time).

I'm not sure how ISS sets its clocks, but the computers are all
networked together, so no doubt they're using the same time reference.
In practice this isn't really a big deal since the difference in
velocity isn't that great.

However the physicists claim that,due to the higher velocity and lower
altitude of the ISS, the direction of the time dilation would reverse.
If it is really true this would indeed be a spectacular demonstration
of the correctness of Einstein's Special and General Relativity, but
I don't believe it myself.

It's complex stuff. You have to take into account both general
relativity and special relativity.

https://en.wikipedia.org/wiki/Time_dilation

Thank you Jeff. The link i gave at the beginning of this post comes
from that same Wikipedia article. The graph i linked to shows clearly
that they are claiming that clocks on the GPS GAIN 37 us/day, while
clocks on the ISS would LOSE 24.6 us/day. I can tell you are convinced,
even without any test on the ISS, but it seems highly improbable to me.

You mean something like this:

NASA - Atomic Clock Ensemble in Space
https://www.nasa.gov/mission_pages/s...ments/2076.htm
l

Atomic Clock Ensemble in Space (ACES) data analysis
https://arxiv.org/abs/1709.06491

So the very thing you propose is planned. It doesn't look like it's
flown to ISS yet though.

At any rate, relativity has been proven many times before.

https://en.wikipedia.org/wiki/Hafele...ing_experiment

A big advantage of doing the test on the ISS would be that the clocks
could be compared while alongside each other, which would be far more
certain and accurate than comparing clocks which are 20,000 km apart,
and moving rapidly relative to each other, as is the case with GPS.

Simple way to do the test on the ISS:
1. Synchronize two clocks.
2. Take one to the ISS.
3. Next flight up take up the other.
4. Compare the two clocks on the ISS.

Much simpler tests have already proven relativity. The equations hold
true. There is no need to think the concept is improbable.

Jeff
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