
Physicists used atomic clocks to test the theory of general relativity - SQL2219
https://www.wired.com/story/these-physicists-watched-a-clock-tick-for-14-years-straight/
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Simon_says
> The concept they tested is similar to Galileo’s apocryphal experiment, in
> which he dropped two objects of the same mass off the Leaning Tower of Pisa
> and found that they fell at the same acceleration regardless of their
> composition.

Typo. Should say of _different_ masses.

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dghughes
>“We’ve moved the lab 14 times around the sun,” says Patla. He’s not trying to
be cute; it turns out that Earth moves through some distinctive regions in
space. Because Earth’s orbit isn’t a perfect circle—its distance from the sun
varies—the clock moved through varying gravitational fields.

Michael from Vsauce has a nice graphic showing that [https://youtu.be/IJhgZBn-
LHg?t=1016](https://youtu.be/IJhgZBn-LHg?t=1016)

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dghf
Quibble: the article refers several times to the theory of general relativity.
I always thought it was the general theory of relativity: i.e., it was the
theory itself that was general, handling everything the special theory
(limited to inertial reference frames) couldn't.

Am I making a distinction without a difference? Are there two forms of the
name in free variation?

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kvakkefly
They are just somewhat different names of the same thing. General relativity
includes the special relativity one where special means without accelerated
reference frames, i.e. nothing accelerates or is exposed for gravity.

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moefh
> special means without accelerated reference frames

That's something a lot of people say, but it's not strictly true. Special
Relativity is fully capable of describing acceleration in a flat (Minkowski)
spacetime[1].

General Relativity is only _really_ needed when there's curvature in the
spacetime (gravity).

[1]
[https://en.wikipedia.org/wiki/Acceleration_(special_relativi...](https://en.wikipedia.org/wiki/Acceleration_\(special_relativity\))

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aks232
That was more interesting than I expected! Good to test basic assumptions
otherwise taken for granted

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ravar
General relativity is not a basic assumption in physics. There is a large
feeling that there is something more out there , but that we don't really know
what it is . Some theories of dark energy or dark matter work by modifying
gravity away from general relativity and in the process create testable
predictions.

~~~
JumpCrisscross
> _There is a large feeling_

Feelings don’t count in science. Every experiment (I am aware of) to disprove
GR has failed. It is the best explanation of spacetime we have.

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whatshisface
It is better than a feeling. GR cannot be quantitized. If anyone describes the
present status of gravity as anything other than a mystery that we are good at
predicting the movements of, they are wrong.

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JumpCrisscross
> _GR cannot be quantitized_

This is irrelevant. GR makes accurate predictions. Perhaps we haven’t figured
out how to quantise it. Maybe it isn’t a quantum field. Maybe we’re mis-
interpreting the mathematics.

Hypotheses are interesting. I find the variable speed of light discipline
neat. But they’re just hypotheses. Until they explain experimental evidence
better than GR, they will remain hypotheses.

~~~
TheOtherHobbes
It's not irrelevant if you're looking for new classes of predictions and new
kinds of experiments - which is one of the motivations for quantum gravity.

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z3t4
My theory is that time runs backwards.

