I Time Dilation Effects of Travel to Star 10ly Away

[virgil1612]

TL;DR Summary

Astronaut's time versus time measured on Earth.

If an astronaut travels to a 10 ly distant star with a speed very close to light speed, then he will measure a distance to his star much smaller than 10 ly (length contraction) so his time for reaching the star will be smaller than 10 years, let's say 1 year. Then, without delay, he returns back to Earth with the same speed, getting back in 2 years (his time).
When he gets back to Earth, will the time elapsed on Earth be just 20 years (20 ly divided basically by the speed of light), or there are GR implications (presumably because of accelerations), that will produce a different result?

 

[pervect]

GR is not required to analyze this scenario. The time will be slightly greater than 20 years back on Earth since the speed is a little lower than "c", but it will be very close to 20 years on earth.

 

[PeroK]

Summary:: Astronaut's time versus time measured on Earth.

If an astronaut travels to a 10 ly distant star with a speed very close to light speed, then he will measure a distance to his star much smaller than 10 ly (length contraction) so his time for reaching the star will be smaller than 10 years, let's say 1 year. Then, without delay, he returns back to Earth with the same speed, getting back in 2 years (his time).
When he gets back to Earth, will the time elapsed on Earth be just 20 years (20 ly divided basically by the speed of light), or there are GR implications (presumably because of accelerations), that will produce a different result?

There are a number of places online (and even some textbooks) that say that SR does not cover acceleration and that GR is needed. This is not right. SR can handle accelerated motion. GR describes gravity: i.e. curved spacetime.

 

[virgil1612]

Great, thank you.