1 A suggested time dilation experiments

2 A suggested time dilation experiments

This is just plain not true: * SR/GR predicts "time dilation" is EXACTLY the same for all clocks, because it is a geometrical projection between inertial frames, which has NOTHING WHATSOEVER to do with any clocks. * SR/GR predicts the difference between elapsed proper times for different paths is EXACTLY the same for all clocks, because it is a difference in path length, which has NOTHING WHATSOEVER to do with any clocks. That is, these effects are GEOMETRY, which is exactly the same for all types of clocks.

What "theory" are you alluding to? References, please.

>	The bold assumption of science is that ALL clocks act the same.

Hmmm. It was bold in 1905, and even in 1916. Today it is old hat, because it is predicted by SR and GR (which are among the best-tested theories we have), and because literally zillions of experiments confirm it.

The decays of unstable leptons and hadrons all behave as SR/GR predicts, as do the atomic clocks of the GPS. These use tim... Show trimmed content

3 A suggested time dilation experiments

But "they" cannot perform an experiment -- that requires real people, not your unspecified pronoun.

The clocks you allude to will not fit into the centrifuge, and will not operate at 20 g.

>	On Saturday, July 14, 2018 at 8:17:56 PM UTC-5, hallst...@gmail.com wrote:

>>

Also, time dilation is NOT due to difference in acceleration or weight, it is proportional to the amount of work needed to lift an object from one location to the other. The centrifuge has 20g acceleration at the end, but the arm is only 29 feet long, so it wouldn't take much work to "raise" an object from the end to the center (where there is no centrifugal time dilation at all). By comparison, in Hafele-Keating there is only about 1g acceleration but the planes are over 30,000 ft up, so the work to lift an object is FAR greater. That's why the time dilation in Hafele-Keating is MUCH greater than for this centrifuge.

>	At 1G I weigh 160 pounds. At 2Gs I weigh 360 pounds. At 3Gs I weigh 540 pounds. Etc. At 20Gs I would weigh 3,200 pounds. And you think it would not require any more work to lift 160 pounds than 3,...

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4 A suggested time dilation experiments

If you want to measure gravitational "time dilation", then you must perform an experiment that depends on it. The centrifuge does not.

SPINNING IS NOT GRAVITATION.

Tom Roberts This message has been deleted.

5 A suggested time dilation experiments

Yes.

>	The only way I can make sense of that is [...]

YOUR GUESSES ARE WRONG.

The centrifuge clock travels a helical path through spacetime, while the lab clock travels a straight-line (inertial) path through spacetime. These paths are manifestly different, and they differ in elapsed proper time by 0.93 ns for this experiment.

This experiment does NOT measure gravitational "time dilation" [#], it is an implementation of the twin paradox and measures the difference in elapsed proper times over different paths through spacetime.

6 A suggested time dilation experiments

What we do is not "pretending to be stationary", but rather we are DEFINING what "stationary" means.

You continually want to introduce some "absolute" or "God's eye" frame that you think is "truly stationary". There _IS_ no such thing. All one can do is specify "I'll apply the word 'stationary' to this frame."

>	In the centrifuge experiment it isn't as much about how fast objects move, it is about GRAVITY.

Nope, if the lab clock is at the same altitude as the centrifuge clock.

SPINNING IS NOT GRAVITATION.

>	[... more nonsense completely irrelevant to this experiment]

Tom Roberts

7 A suggested time dilation experiments

8 A suggested time dilation experiments

For this problem in particular, switching to Python's decimal module is a bit of overkill. Since v << c, we can just use the first terms of a Taylor series expansion.

using my old TI-89 v = 46 c = 299792458 gamma = 1/sqrt(1 - v^2/c^2) ˜ 1/(1 - 0.5 * v^2/c^2) ˜ 1 + 0.5 * v^2/c^2
= 1 + 1.1771837593048e-14 = 1.000000000000011771837593048
1.1771837593048e-14 * 22 * 3600 = 9.32e-10 seconds

>

from decimal import * v = Decimal(46.0) c = Decimal(299792458.0) gamma = Decimal(1.0)/Decimal.sqrt(Decimal(1.0)-v*v/c/c) t = 22*3600 delta_t = Decimal(t) * (gamma-Decimal(1.0)) print(gamma,delta_t) 1.000000000000011771837593048 9.32329537369401600E-10 So after 22 hours, the clock in the centrifuge is predicted to lag the clock in the lab by 0.93 nanoseconds.

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9 A suggested time dilation experiments

True. However, as there is acceleration involved in spinning, does the Einstein equivalence principle not imply the same observations (in addition to those explained by relative motion) as if the system in question would not be spinning, but were in a gravitational field?

10 A suggested time dilation experiments

That, of course, was the point that I was trying to make in my post of July 15, 2018 at 11:32:58 PM UTC-5 on this thread.

In Roberts' post of July 13, 2018 at 3:22:40 PM UTC-5, the lab observer calculates the time dilation as being strictly due to the speed of the clock relative to the lab.

In my post, the moving observer on the circumference of the centrifuge calculates the frequency shift of a light beam between himself and the center as being due to the difference in potential between himself and the center due to the centrifugal (pseudo)force.

11 A suggested time dilation experiments

12 A suggested time dilation experiments

You are supposed to read what I write before attempting to respond. Earlier in that post I said:

(In this case, after the comma I also gave two examples of quantities that do slow down (or speed up) or differ.)

Given that you do not understand general rhetorical patterns [#], it's no surprise that you get so many things wrong. YOU REALLY NEED TO LEARN HOW TO READ.

[#] After disagreeing with an opponent's incorrect claim, giving related examples that are correct.

>>	[H&K's clocks] specified by their manufacturer to operate only under accelerations less than 2 g. After all, they use an atomic beam in freefall, and at 20 g it will not remain in the waveguides used to measure its frequency; the mechanical structure might not remain stable.

>	They are specified to be used at less than 2Gs because above 2Gs you will get measurable gravitational effects that may cause you to reset your clock if you have no interest in those effects.

Nope. YOU DO NOT UNDERSTAND THIS -- gravitational "time dilation" is NOT related to the acceleration of the clocks, it is related to the difference in their gravitational potentials; it is a comparison of two clocks located at different gravitational potentials, and does not affect a single clock. As I keep saying: CLOCKS ALWAYS TICK AT THEIR USUAL RATE.

There _ARE_ no "gravitational effects" that affect a single clock [%]. Such clocks are specified to operate at less than 2 g because larger accelerations could damage them.

13 A suggested time dilation experiments

Sure. But I doubt very meany people around here understand that, so I chose the simpler approach of using a "calculator" with sufficient significant digits.

Tom Roberts

14 A suggested time dilation experiments

Yes, within limits. Here we meet those limits and can consider the rotating centrifuge to be "generating" an equivalent gravitational field in its rotating frame. Note that in these coordinates the centrifuge clock is not moving; let's place the lab clock at the center of rotation, so it is also not moving relative to these coordinates (and is also not moving relative to the lab).

Here are three calculations of the difference in elapsed proper time between the centrifuge and lab clocks:

1. Centrifuge clock's "time dilation" relative to the lab frame: sqrt(1-v^2/c^2), with v the clock's speed relative to the lab, measured in the lab. Integrate this over 22 hours and one gets 0.93 ns over 22 hours.

2. Centrifuge clock's "equivalent gravitational time ...

Tom Roberts