Combining Time Dilation from velocity and gravity

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Discussion Overview

The discussion explores the combined effects of time dilation due to both relative velocity and gravitational influence near a massive black hole. It examines how these two factors interact when considering the perspective of a stationary observer and astronauts aboard a spaceship traveling at a significant fraction of the speed of light.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant proposes a scenario involving a spaceship traveling at 0.866c near a black hole, suggesting significant time dilation effects from both special and general relativity.
  • It is noted that for every hour experienced by the astronauts, 2 hours pass for a stationary observer due to special relativity, and similarly, 2 hours pass for the observer due to general relativity.
  • Another participant discusses the observed time on stationary clocks at the ship's position and the ship's clock, indicating a potential multiplicative effect of the time dilation factors.
  • A reference to a similar thread is made, suggesting that this topic has been discussed previously in the forum.

Areas of Agreement / Disagreement

Participants appear to be exploring the interaction of time dilation effects, but there is no consensus on the exact nature of the combined effect or its implications.

Contextual Notes

The discussion does not resolve the mathematical steps involved in determining the combined time dilation effect, leaving assumptions and dependencies on definitions unaddressed.

edgepflow
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Suppose a stationary observer was watching a spaceship travel near the speed of light and close to a massive black hope so that time dilation from the relative velocity and gravity of the massive object are significant.

Assume that the ship is moving at 0.866c so that for every hour that passes for the ship's astronauts, 2 hours pass for the for the stationary observer per special relativity.

Now also assume, that the ship is close enough to the black hole so that for every hour that passes for the ship's astronauts, 2 hours pass for the for the stationary observer per general relativity.

So the question is: what would be the combined effect?

P.S. I meant to post this in the Relativity Forum!
 
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edgepflow said:
P.S. I meant to post this in the Relativity Forum!

Moved
 
what would be the combined effect?
So in 1 hour of your time, you see stationary clocks at the ships position tick 1/2 hour.
They see the ship clock tick 1/4 hour - and so do you.
 
Ich said:
So in 1 hour of your time, you see stationary clocks at the ships position tick 1/2 hour.
They see the ship clock tick 1/4 hour - and so do you.
Thanks for the reply Ich. It looks like the combination is multiplicative. I also noticed this under Similar Threads that discusses this.

https://www.physicsforums.com/showthread.php?t=299318
 

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