Acceleration vs Gravity and effect on time/clocks

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Discussion Overview

The discussion revolves around the relationship between acceleration, gravity, and their effects on time as measured by clock-type devices. Participants explore theoretical implications and practical examples, particularly focusing on radioactive decay rates in an ultra-centrifuge and the concept of time dilation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants reference Einstein's assertion that acceleration cannot be distinguished from gravity under certain conditions, questioning its implications for time measurement.
  • One participant suggests that radioactive decay rates in a spinning ultra-centrifuge would be slower, citing experimental evidence related to special relativity.
  • Another participant emphasizes the need for careful interpretation of decay rates, attributing the observed slowing to time dilation effects rather than acceleration itself.
  • It is proposed that gravitational time dilation is linked to gravitational potential rather than acceleration, with examples involving clocks at different heights in a uniform gravitational field.
  • A scenario is presented where two clocks in an accelerating spaceship would experience different rates, with the clock at the front running faster than the one at the back, despite both experiencing the same acceleration.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of time dilation effects related to acceleration and gravity, indicating that multiple competing perspectives remain without consensus.

Contextual Notes

Participants note the importance of distinguishing between gravitational potential and gravitational acceleration when discussing time dilation, highlighting that interpretations may depend on specific conditions and setups.

DarioC
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Just kicking some things around and this came up:
Albert says that it is not possible to discern acceleration from gravity under his imposed conditions.
Question, does that apply to clock type "devices," and time?

As practical example; let us put a radioactive sample in an ultra-centrifuge and spin it up, monitoring the average radio-active decay rate. Will it be slower?
 
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DarioC said:
Just kicking some things around and this came up:
Albert says that it is not possible to discern acceleration from gravity under his imposed conditions.
Question, does that apply to clock type "devices," and time?
Yes.

DarioC said:
As practical example; let us put a radioactive sample in an ultra-centrifuge and spin it up, monitoring the average radio-active decay rate. Will it be slower?
Yes. If you click on the sticky thread on experimental basis of SR and search for muon you will find some experiments (Bailey?) about exactly that.
 
DarioC said:
Just kicking some things around and this came up:
Albert says that it is not possible to discern acceleration from gravity under his imposed conditions.
Question, does that apply to clock type "devices," and time?

As practical example; let us put a radioactive sample in an ultra-centrifuge and spin it up, monitoring the average radio-active decay rate. Will it be slower?

While the decay will be slower in the centrifuge, you have to be really careful how you interpret this. The slowing is exactly that which you would expect from time dilation for a clock traveling at the speed of the end of the centrifuge. The acceleration itself does not add any extra time dilation.

This can be shown by using centrifuges with different arm lengths if the speed at the end of the arm is kept constant, the time dilation remains the same, even though the acceleration experienced will be different.

So how do we equate gravity and acceleration when it comes to time dilation? First you have to realize that gravitational time dilation is related to gravitational potential and not gravitational acceleration. If you had a uniform gravity field (one that did not differ in strength with height) and put two clocks in it at different heights, the higher one would run faster compared to the lower even though they feel the same pull of gravity.

With acceleration, this same effect can be shown by having two clocks sitting in the nose and tail of an accelerating spaceship. The clock in the nose willing run faster than the one in the tail, even though they are both accelerating at the same rate.
 
OK, thanks for the references. The one on "clock" velocity vs acceleration was most interesting.
DC
 

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