# A little bit of paradox

1. Sep 9, 2010

### Minatory

Here comes the model situation. I have a man on a planet and two ships. One ship will go straight to from a planet and another one will go opposite direction. Well thats for me very interesting.

Because i will travel with ship near to speed of light from earth the earth time will be for me slowed down. But I also traveling on a ship from another ship with doubled speed but thats impossible - nobody can cross a speed of light - so time on other ship must be also very slowed down.

And question. When everybody will came back at earth who will be oldest?

2. Sep 10, 2010

### Parlyne

Under the (usual) assumption that, for such problems, we neglect the small effects due to Earth's orbital and rotational motion, and the effects of both Earth's and the sun's gravity, the answer is that the observer who stayed on Earth the whole time will be oldest. The simplest way to put this is that (in special relativity) the path of longest proper time between two time-like separated events is the path that involves no acceleration.

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