Radioactive decay in relativistic frames

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Discussion Overview

The discussion centers around the effects of relativistic frames on radioactive decay, particularly comparing samples on Earth and in high-speed motion, as well as the implications of gravitational effects on decay rates near massive bodies like black holes. The scope includes theoretical considerations and conceptual clarifications related to time dilation and decay rates in different environments.

Discussion Character

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

Main Points Raised

  • One participant questions whether a radioactive sample on Earth will undergo more decay than an identical sample on a near-lightspeed spaceship, suggesting that the Earth sample would decay more if compared after returning to a stationary state.
  • Another participant asserts that the sample on Earth will decay faster than one on a lead planet, without providing detailed reasoning.
  • A claim is made that the sample on the surface of Earth will decay faster than one at its center, though the reasoning is not elaborated upon.
  • A participant references the observation of muons produced from cosmic rays, noting that they live longer than expected due to relativistic effects, implying a connection to the discussion on decay rates.
  • There is speculation about time dilation effects near a black hole, questioning whether time behaves discontinuously at the center and whether a bridging theory is needed between known physics and singularity physics.
  • Another participant describes the differing perspectives of an outside observer and an object falling into a black hole, highlighting the contrasting experiences of time and decay rates in different reference frames.

Areas of Agreement / Disagreement

Participants express differing views on the effects of relativistic motion and gravitational influence on radioactive decay, with no consensus reached on the implications of these effects in extreme environments like black holes.

Contextual Notes

Limitations include assumptions about the conditions of the experiments, the definitions of decay rates in different gravitational fields, and the unresolved nature of the physics at singularities.

Tyro
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If you take two identical radioactive samples, place one on Earth and another on a near-lightspeed spaceship, and compare them some time later, will the one left on Earth have undergone comparatively more radioactive decay than the one on the spaceship?

If the experiment is repeated by leaving one on Earth and another on a planet with the same radius as Earth but made entirely of lead, what, if any, will the difference be?

Finally, how would the radioactive decay of a test source on the surface of Earth and its centre compare?
 
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Originally posted by Tyro
If you take two identical radioactive samples, place one on Earth and another on a near-lightspeed spaceship, and compare them some time later, will the one left on Earth have undergone comparatively more radioactive decay than the one on the spaceship?

Yes. (assuming that the second sample is brought back to a state where it is motioness wrt the first when the comparision is made. )


If the experiment is repeated by leaving one on Earth and another on a planet with the same radius as Earth but made entirely of lead, what, if any, will the difference be?

The sample sitting on Earth will decay faster.


Finally, how would the radioactive decay of a test source on the surface of Earth and its centre compare?

The sample on the surface will decay faster.
 
This relativistic effect on decay time has been obseved. Muons produced from cosmic rays come to Earth at speeds close to c. As a result they live longer than expected.
 
Does that mean that time dilation slows time down to a near standstill as you near the centre of a black hole, but the second (excuse the pun) you hit the centre, time goes discontinuously back to normal?

Or is it generally accepted that some kind of bridging theory must be made between physics as we know it and the physics at a singularity, thus making the above interpretation speculative?
 
An outside observer sees something falling into a black hole slow down and never fall in. In fact, to the outside observer, the black hole never formed.

On the other hand, an object falling in would be in a different reference frame and would simply pass the event horizon and quickly be destroyed.
 

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