I am aware of the idea of time dilation (which I, by the way, asked another question about) on speeds, that get close to the speed of light. Though, I wonder what other (if any) forces and laws affect time passing on other planets and in interstellar.

The following thought experiment might illustrate (at least I hope it will) what I am asking:

Say we have 10 clocks that run forever (i.e. they do not require rewinding at all), are perfectly synchronized and are not damaged by any external conditions on other planets (high temperatures, acids etc.). Now let's assume we have put a clock on the surface of each planet in our Solar System (i.e. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto). Let us also assume that we never approached speed of light while transporting the clocks (say we used space bicycle, or something :-). The 10-th clock — we just released it (somewhere behind the Pluto, perhaps) to drift into interstellar space. Then we came back to Earth and waited (according to the clock we left on Earth) for exactly 1000 hours.

  1. Assuming that nothing would cause clock in interstellar to move close to the speed of light, what time will be displayed on each of the clocks (given we could, somehow, check it simultaneously)?

  2. Would the results differ if we were able to synchronize all the clocks, exactly at the moment we started counting our 1000 hours from?

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    $\begingroup$ Hi Filipp. The duplicate I've suggested above specifically refers to Mars but the answer applies to all planets. $\endgroup$ Commented Nov 18, 2018 at 15:50
  • $\begingroup$ Thanks, @JohnRennie, read&upvoted =). What about interstellar space? Would it be the same, but omitting the 3-rd step of ΔΦ calculation (i.e. addition of the (negative) potential energy change to descend to the surface of the planet)? $\endgroup$
    – user187075
    Commented Nov 24, 2018 at 8:23
  • $\begingroup$ Yes. You'd consider only the potential energy change moving in to the orbital radius then down onto the surface of the planet. $\endgroup$ Commented Nov 24, 2018 at 9:29

1 Answer 1


The thing in interstellar (the film) was that the planet had extraordinary gravity and rotational speeds, if I remember correctly? In which case it was the rotational speeds which caused time dilation.

A) We all know films aren't that accurate, they take an idea and run with it!

B) in your scenario it appears the clocks are just being released into space at no great speed, in which case, there should be no real difference in their times. It is all to do with your speed relative to the speed of light.

That being said, the clocks on the International Space Station do run a little differently to ours here on earth, due to the fact that they are going at a different speed to us! Similarly, as your head is going at a different speed to your feet, they will be slightly different ages when you pass away. I hope this makes sense.

In short - there will be a minor effect only where there are speed differences, and only ever noticeable/measurable when involving speeds close to the speed of light!

  • $\begingroup$ The time dilation in Interstellar was caused by the planet being extremely close to a black hole (the planet's own gravity would likely not have contributed very much to this effect). This is confirmed by the existence of enormous tides on the surface of the planet, caused by the influence of the black hole's gravity. I don't follow your logic as to why rotational speeds would cause time dilation. $\endgroup$ Commented Nov 18, 2018 at 15:58