Who Experiences 50 Light Years Differently: The Astronaut or Mission Control?

[Kkamann]

Suppose you were traveling from Earth to a destination 50 light years away on a spaceship traveling at 99.99% the speed of light. So who has to wait the full 50 years for the ship to arrive at the destination? The mission control guy sitting in Houston? Or the pilot of the spacecraft ?

I'm not a physicist, nor even work in a science-related field. I'm just a regular dude who finds such things rather fascinating. So please be gentle. I apologize if this question is rediculously rudimentary and it may not seem like rocket science to most of you. But I suppose it is, come to think of it.

 

[mathman]

The mission control guy waits 50 years, while the pilot takes almost no time. When he return back to Earth he finds 100 years have elapsed, while he may have aged only a few days - depending on how close to the speed of light he was able to go.

 

[ghwellsjr]

Suppose you were traveling from Earth to a destination 50 light years away on a spaceship traveling at 99.99% the speed of light. So who has to wait the full 50 years for the ship to arrive at the destination? The mission control guy sitting in Houston? Or the pilot of the spacecraft ?

I'm not a physicist, nor even work in a science-related field. I'm just a regular dude who finds such things rather fascinating. So please be gentle. I apologize if this question is rediculously rudimentary and it may not seem like rocket science to most of you. But I suppose it is, come to think of it.

The answer depends on what you mean by waiting. If you are asking how long it will take for the mission control guy to get radio confirmation that you have arrived at your destination, then it will take a little longer than 100 years because it will take you just over 50 years to get there and another 50 years for your radio signal to get back to Earth announcing your arrival. If you mean how long he can assume that it takes you to get there without knowing for sure, then the answer would be just over 50 years.

But from your point of view, because of time dilation, it will take you only 8 and a half months to get there.

 

[phinds]

But from your point of view, because of time dilation, it will take you only 8 and a half months to get there.

I assume that doesn't count some decent deceleration that will keep the occupants from turning to jello and that WITH such a deceleration (and the similar acceleration on the front end and starting off on the way back), it would take WAY longer

 

[Mike_Fontenot]

I assume that doesn't count some decent deceleration that will keep the occupants from turning to jello and that WITH such a deceleration (and the similar acceleration on the front end and starting off on the way back), it would take WAY longer

With 1g accelerations, it would take the traveler longer, but still MUCH less than 100 years ... he will still be MUCH younger than his friends on Earth when he gets back. For an example with 1g accelerations, see my webpage:

http://home.comcast.net/~mlfasf

Mike Fontenot

 

[JesseM]

Suppose you were traveling from Earth to a destination 50 light years away on a spaceship traveling at 99.99% the speed of light. So who has to wait the full 50 years for the ship to arrive at the destination? The mission control guy sitting in Houston? Or the pilot of the spacecraft ?

The distance between Earth and the destination itself depends on the choice of reference frame, I assume it's meant to be 50 light years in the frame where both Earth and the destination are at rest? In that case it will take about 50 years for the spaceship to get there in this frame, but in the ship's frame the distance will be much shorter due to length contraction, so the time is shorter as well.

 

[ghwellsjr]

...return back to earth...

...on the way back...

...when he gets back...

Did Kkamann say anything about coming back?

 

[Kkamann]

It was intended to be just a simple question of whose perpective it is when one says light-year. LOL I didn't feel it necessary to type out all the caveats about subspace communications, round trips, or being turned into chunky salsa when you hit the brakes. But I suppose I should have. After all, we are talking with a bunch of physicists here. Sooo...

It's a one-way kamikaze mission to take out a stationary (relative to Earth) outpost whose inhabitants who have the will and the means to destroy Earth but strangely do not have the ability to detect my ship until it's too late (relative to the outpost, of course). Oh, and my spaceship has inertial dampeners and instant communication stones. And anything else I haven't thought of yet will be handled deftly with my magical powers (And no, I will not simply wipe out the outpost by zapping them with my magical powers. Why? Because I choose to do it this way. Why? Because my god-like powers have made me rather eccentric).

Does that help?

 

[ghwellsjr]

It was intended to be just a simple question of whose perpective it is when one says light-year. LOL I didn't feel it necessary to type out all the caveats about subspace communications, round trips, or being turned into chunky salsa when you hit the brakes. But I suppose I should have. After all, we are talking with a bunch of physicists here. Sooo...

It's a one-way kamikaze mission to take out a stationary (relative to Earth) outpost whose inhabitants who have the will and the means to destroy Earth but strangely do not have the ability to detect my ship until it's too late (relative to the outpost, of course). Oh, and my spaceship has inertial dampeners and instant communication stones. And anything else I haven't thought of yet will be handled deftly with my magical powers (And no, I will not simply wipe out the outpost by zapping them with my magical powers. Why? Because I choose to do it this way. Why? Because my god-like powers have made me rather eccentric).

Does that help?

As JesseM pointed out, you should state whose perspective it is when you state a distance but since you also stated a speed and there are only two perspectives mentioned, it would be reasonable to assume that you were assigning the distance from the same perspective as the speed was assigned and if it had to be one of those two, then that would make it from the Earth rest frame and my answer previously given in post #3 would apply.