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If I am traveling in a spaceship with uniform motion near the speed of light towards a stationary observer on Earth, assuming I am not aware of the situation, then I would assume that Earth is approaching me at approximately the speed of light. Where is time passing slower now?

According to the theory of relativity, both the observer and I would believe that time is passing more slowly for the other. How can both be true? Nobody would be wrong with that Assumption. It is a fact that time is passing slower for both of us in a way.

CherryBlossom1878
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    Where is time passing slower for whom? – Jon Custer Jan 29 '24 at 16:22
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    You have come upon what is known as "The Twin Paradox" where we attempt to discover which twin is younger after such a trip. There is a ton of stuff written about this, including many many videos. I strongly suggest that you watch https://www.youtube.com/watch?v=nRuVGOm7560 and https://www.youtube.com/watch?v=FGoAZKyI6ZY that will both explain the real problems with the various explanations you will see. – foolishmuse Jan 29 '24 at 16:24
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    Different observers have different notions of time. both observers measure their time to move faster than the other. There is no contradiction. – Prahar Jan 29 '24 at 17:03
  • Every clock runs faster in its own frame than in any other. – WillO Jan 29 '24 at 17:30

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The light from earth will be blue shifted and everything you see on earth will appear speeded up by the same factor. The people will run faster, cars will travel faster etc.

The earthlings looking up at you will also see the light from you blue shifted by the same factor, and so they will see you move faster than if you were at rest.

If you were moving away from earth everything would appear to be moving slower for both you and the earthlings.

Where is the paradox with this?

mike stone
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  • The OP asks "where does time run slower?" The wording is suboptimal but it seems clear to me that this is not a question about doppler shifts, but rather a question about the speeds of clocks in various frames. – WillO Jan 29 '24 at 17:29
  • @WillO "time" (or clocks) do not "run slower" in moving frames. Clocks observed from different frames appear to run slow or fast, and that is exactly what the Doppler shift is. The twin "paradox" is a different matter. – mike stone Jan 29 '24 at 20:39
  • Again, the original question is too poorly worded for either of us to be sure what's meant, but the OP never mentions appearances. And of course every clock certainly does run slower in some frames than it does in others. – WillO Jan 29 '24 at 21:49