travel at .9c

[Solfe]

I am familiar with the idea that traveling one year on a ship at .9c would be equal to 2.3 (roughly anyway) years back on Earth due to time dilation. This means a 10 year journey (ship time) would be 23 years back on Earth. Assuming there were people waiting at the destination (Planet H) already, would they be using the same clock as people on Earth? IE a 23 year travel time?

As a follow on question, what about two ships launched 1 year apart from Earth to Planet H, how would the first ships clock be different from the second ships clock? If Ship 1 launched on Jan 1, 2020 at .9c from Earth and Ship 2 launched in 2021 at .9c (they have really cool engines), on arrival would the passengers from Ship 1 have to wait more than a year for the passengers on Ship 2 to arrive on Planet H?

Thank you in advance,

[Trakar]

I am familiar with the idea that traveling one year on a ship at .9c would be equal to 2.3 (roughly anyway) years back on Earth due to time dilation. This means a 10 year journey (ship time) would be 23 years back on Earth. Assuming there were people waiting at the destination (Planet H) already, would they be using the same clock as people on Earth? IE a 23 year travel time?

As a follow on question, what about two ships launched 1 year apart from Earth to Planet H, how would the first ships clock be different from the second ships clock? If Ship 1 launched on Jan 1, 2020 at .9c from Earth and Ship 2 launched in 2021 at .9c (they have really cool engines), on arrival would the passengers from Ship 1 have to wait more than a year for the passengers on Ship 2 to arrive on Planet H?

Thank you in advance,

ignoring the very big issues of accelerating to .9c and from .9c, as well as the problems of travelling at much more than .4c, and looking at only the relativity and time dilation issues. If ship 2 launched 1 year after ship 1 and travelled at the same speed as ship 1, it would arrive at the same destination 1 year after ship 1 did. To outside observers (Earth and planet H) the ships would travel at 0.9c and take 23 years for the transit respectively.

[kamaz]

Assuming there were people waiting at the destination (Planet H) already, would they be using the same clock as people on Earth? IE a 23 year travel time?


Assuming that Planet H does not move with respect to Earth (or moves at non-relativistic speed), yes. Otherwise, see this: http://en.wikibooks.org/wiki/Special_Relativity/Spacetime

[Solfe]

Cool. the answer actually make sense to me, which is a bonus. Thank you both.