A question about space travel

Hello all ..

I'm sure my question isn't worthy of its own thread and i don't
mind if the mods take it away, but if someone could u2u me
if that happens, thats cool .. oh by the way .. i did ask this question
in another thread but haven't had an answer so i thought id' do
this thread .. in fact here's my question from that thread ..

Quoting myself from a previous thread ..

"First off my knowledge of space the planets
and travel in space are very basic .. as in
school stuff and stuff read online or watched
on tv etc .. but i have had this thought for a
while now .. i read that if you could travel
at the speed of light say to Mars, by the time
you got back to Earth everyone would have
dramatically aged more than you .. i sort of
get that .. but my question is .. if someone
travelled to Mars at the same speed as the
rovers that are there would the same thing
apply if they returned ?? or does that theory
just apply to travelling at the speed of light ??
The reason i ask is because if you answered
that yes people would age more when you return
after travelling to and from Mars at the same speed
as the Mars rovers .. well wouldn't the signals we send
to these rovers at present, to make them move
, dig etc, wouldn't we be sending them back in time ??

Hang on i recon i've hurt my mind thinking
that one .. but see if you can get your head
around what i'm saying .. "

Regards

satellite1

I think that the theory that time slows with the speed we are moving was proved (or at least it was made stronger) by an experiment where they flew for some time (on an aeroplane) an atomic clock synchronised with another atomic clock exactly like the first but that stayed stationary, and when the "flying" clock returned it was a little late, when compared with the one that never left the laboratory.

I don't know if this applies to light itself (or any other electromagnetic waves), but if it does, and as light travels at the speed of light (obviously ), then time does apply to light, it's as if time has stopped.

This does not affect the receiver of the light (or electromagnetic wave), it will receive it regardless of the way time passes to the light, in the same way the people that received the "flying" clock were not affected by the fact that time passed slower to it.

I hope that helps.

reply to post by satellite1

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Time dilatation for an object with mass, according to Einstein relativistic theory (proved countless times), varies with the velocity of the object. The more the velocity approaches the velocity of light (c), the larger is the time dilatation, as well as other relativistic effects.

So, yes, a craft going to Mars would be affected by this, but since the velocity is so smaller than c, this effect can not be perceived.

EDIT: I mean, the effect could be measurable, but it's negligible.

[edit on 6-5-2008 by borek]

[edit on 6-5-2008 by borek]

reply to post by borek

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Thanks for your replies ppl ... ok .. so lets say we have a rover on Mars right now .. how long does the signal take to get to it from earth .. is this signal affected by time ?? i suppose what i'm asking is .. is anything and everything affected by time dilation ?? if this is the case then we must be sending the signal back in time .. .. oh dear .. i'm blowing my own head in with this .. lol .. do you understand what i'm saying or is it coming out all giberish .. sorry in advance ..

regards

satellite1

reply to post by satellite1

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I think I see what you mean. The answer is yes and no.

First, consider that the "message" you're sending is actually a small object with mass and v < c. The time dilation will only be perceived by a possible clock traveling with the object, on its own reference frame.

On our reference, the time taken for the "message" to reach Mars, in this case, will be the normal t = v / distance. So, for us, it would not make any difference.

For light, if you apply the equations, you can see that on the light's reference, the time dilation would increase infinitely. So, it does not make much sense to consider the "light's reference". For all the references other than the light's one, including our own and the craft on Mars, light always travel at the velocity c. So the time it takes for a eletromagnetic signal to reach Mars is just t = c / distance. No correction or time travel is involved.

So, my answer is 'yes': relativity affects everything, but 'no', since it does not make sense to consider the "light's own reference", light travels at a constant velocity c no matter what.

All this talk is not only theory: it has been measured and verified. But obviously physical interpretation of the results is always up to debate.

Thanks for your explanation ..

I don't think i should spend anymore time
thinking of this .. it hurts the mind .. although
its good to get the mental cogs working
now and again ..

Kind regards

satellite1