relativity question (1 Viewer)

[pseudo]

just a question about high velocity space travel

if u were travelling near the speed of light then time would slow down for you relative to those outside. therefore any fuel which you were using would be used at a much slower rate

this means that a small supply which lasts a few days on the ship would last for a comparitively long time when concerning the journey from the perspective of those on earth

is this true or is my theory flawed somehow? any comments welcome

 

[...]

it can be tricky..


E=mc^2

the energy u put in to get into speed of light(or close) will be massive...
think of mass dilation, the faster u travel, the heavier ur suppose to be to the observer..so the fuel needed should be greater...

 

[pseudo]

but u r not heavier in your own frame of reference so ur mass shouldnt matter

 

[...]

thats y this is very tricky...

however, to be able to reach very high speed(close to 'c'), the current technology will still require a lot of energy to be able to reach that speed...

 

[LadyMoon]

The great Lady Moon: the cousin of Einstein by marriage
(above is bullshit, fact follows below)
Actually your theory is flawed

because the fuel tank is actually travelling with you! thus in the same frame of reference as you..thus time is not slowed for it

 

[...]

what i am thinking is..

to the traveller...the fuel will run out rather quickly..lot quicker than normal

 

[pseudo]

time is slow for the fuel tank cause it is with you at a high speed so it will only be operating for a few days like you but in reality the ship will have travelled for months to a far away place

 

[Son_e_boy]

I know what you mean pseudo...

Sometimes they talk about relativistic travel and say you can't travel at that speed because your mass will increase infinitly, but its only percieved to be heavier by people viewing a spacecraft from earth.

If the space craft was the experience the increase in mass it violates the principle of relativity; when in a inertial frame of reference you cannot tell whether you are moving or still unless if you refer to another frame of reference.

 

[CHUDYMASTER]

I'm afraid not.

The mass does not get consumed slower for occupants' frame of reference as has already been stated. An external observer will see the fuel be consumed slower ONLY because the ship will also be going slower as perceived by them.

 

[pseudo]

i didnt ,mean getconsumed slower for the people on the ship but because the journey is shorter as they percieve it they wouldnt use as much fuel

 

[CHUDYMASTER]

Ok, they WILL perceive an outside frame of reference to contract assuming it too is in an inertial frame of reference. However, it will also experience time dilation, meaning that it will appear to take longer to get there. As a result, the two cancel out and the net rate will still be the same.

 

[pseudo]

it takes longer from the outside frame of reference not on the ship there is no canceling out that occurs

also as the ship is accelerating there is no need for an outside frame of reference

 

[LadyMoon]

ok
when you are accelerating, you are not in a different frame...thus you need A LOTTA fuel to to accelerate to 3*10^8 m/s.

there is another reason why it aint possible

 

[pseudo]

it might take a lot of fuel to begin with but as you accelerate towards the speed of light times slows down and therefore fuel lasts longer

 

[ND]

Yep i think you're right. It's similar to the muon thing, theoretically (when special relativity is not considered) they should never reach the earth, but they've been detected. I also remember reading something about radioisotopes they accelerated and found that they got further than they theoretically should have (before they decayed completely).

 

[Dangar]

I agree with you too pseudo, cos once you've reached this fast speed you'll get length contraction, so the distance you travel becomes shorter therefore you consume less fuel.

but your time will remain the same... it'll only appear slower to an observer so time will have no effect upon the rate of fuel consumption.

 

[ND]

I disagree Dangar, i think it's because of the time dilation. Compare it to the radioisotopes; they travel further because time dilation means that their half-lives are lengthened. In this case, the rate at which the RI's decay can be seen as the rate at which fuel is consumed.

 

[Dangar]

hmm i don't really understand...is there somewhere i can read about these isotopes??
Going by the muon theory, they should only be able to travel a short distance, but they reach earth becos of length contraction right? In their own frame of reference their time doesn't slow, it only slows for an observer so they still only exist for a short time period according to themselves but they travel a lot further...
aah i think im getting a bit muddled, can anyone clear this up for me? plz..

 

[ND]

Actually i think the muons also are able to reach the earth because of time dilation. I don't really know anything about muons, i just remember that in a question (in some trial i think) they said that theoretically a muon shouldn't reach the earth, but they do, and then proceeded to ask a calculation of time dilation. About the RI's, try googling it, that's where i found it i think.

edit: here's a site with some info:

http://www2.slac.stanford.edu/vvc/theory/relativity.html

Go down to where they talk about time dilation for particles.

 

[Constip8edSkunk]

but isnt length contraction and time dilation 2 sides of the same coin anyway?