Mick's Spooky Time Dilation Puzzle

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Discussion Overview

The discussion revolves around the effects of gravitational time dilation and orbital time dilation on astronauts, particularly in the context of different altitudes and orbits. Participants explore the implications of these effects on timekeeping for satellites and astronauts, as well as philosophical musings about the nature of time.

Discussion Character

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

Main Points Raised

  • Some participants propose that gravitational time dilation (speed up) may cancel out orbital time dilation (slow down) for astronauts, but this is conditional on the altitude of the orbit.
  • One participant explains that for low Earth orbit, the slow-down due to orbital speed is greater than the speed-up from altitude, resulting in clocks on the ISS running slower than those on Earth.
  • Another participant notes that at the altitude of GPS satellites, the altitude effect outweighs the orbital speed effect, leading to GPS clocks running faster than Earth clocks, necessitating a frequency correction.
  • One participant asserts that GPS satellites require specific corrections for time dilation effects, indicating that in geosynchronous orbit, the time dilation effects do not cancel out.
  • A participant expresses a philosophical perspective on the nature of time, questioning whether the past and future influence the present.
  • A later reply reminds participants to adhere to forum rules regarding personal speculation, suggesting that philosophical musings may not align with the technical focus of the discussion.

Areas of Agreement / Disagreement

Participants express differing views on the interaction between gravitational and orbital time dilation, with some asserting that they do not cancel out while others suggest that this may depend on specific conditions. The discussion remains unresolved regarding the exact nature of these interactions.

Contextual Notes

Participants mention specific altitudes and their effects on time dilation, but the discussion does not resolve the complexities of these interactions or the exact conditions under which they apply.

AtoMick-u235
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Hmmm, , Does gravitational time dilation (speed up) cancel out earth orbit time dilation (slow down) for astronauts, , , it must do, to a certain extent

Hmmm, , ,Mick's been thinking = the present is a continuous but fleeting moment, that allows the future to flow into the past, , ,so does the past and future push and pull the present ?, , , SPOOKY !!
 
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AtoMick-u235 said:
Does gravitational time dilation (speed up) cancel out earth orbit time dilation (slow down) for astronauts, , ,
It depends on what altitude the astronauts are orbiting at. For low Earth orbit (such as the ISS), the slow-down due to orbital speed is greater than the speed-up due to increased altitude, so clocks on the ISS run slower than clocks on Earth.

At the altitude of the GPS satellites, however (orbital radius of 4.2 Earth radii), the opposite is true: the altitude effect outweighs the orbital speed effect so the natural rate of clocks on the GPS satellites is faster than that of Earth clocks (and so a frequency correction has to be applied to the GPS satellite clocks so that the output "tick rate" is the same as that of Earth clocks).

The break point between these two regimes is at an orbital radius of 1.5 Earth radii, or an altitude above Earth's surface of 0.5 Earth radii, or about 3200 km.
 
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No, GPS satellites need to account for -7 microseconds/day due to SR (motion) and +45 microseconds/day due to GR (gravity).

SO ... if an astronaut is in geosynchronous orbit, the answer is obviously no. You could probably find the one exact orbital path for which the difference is zero, but in general ... no.

EDIT: I see Peter beat me to it.
 
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AtoMick-u235 said:
Mick's been thinking = the present is a continuous but fleeting moment, that allows the future to flow into the past, , ,so does the past and future push and pull the present ?, , , SPOOKY !!
Please review the PF rules on personal speculation. Your initial question was fine by itself.
 

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