Nutshell

Hi,

I have heard AND seen in movies that if you move at light speed or at least very very fast in space, and when u come back to earth, all other people will be much older than you do. Sounds scary.....is this true?

Einstein

Very true
http://www.google.com/search?hl=en&n...=time+dilation

shtarker

http://www.cprogramming.com/cboard/s...threadid=14138

Shiro

>I have heard AND seen in movies that if you move at light speed
>or at least very very fast in space, and when u come back to
>earth, all other people will be much older than you do.

This is known as the twin-paradox and not true.

shtarker

No the twin paradox was that from the Earth's point of view you have aged less, but from your point of view the earth has aged less.
In reality if a person travels near the speed of light, they will age much slower then normal. So yes, planet of the apes (the original) is possible.

Nutshell

that movie is cool

i was just wondering that'll be pretty scary if you gone out to space and come back and find that everything u familiar wif is gone.....

incognito

As seeing as a guest of this board chose the username Einstein, now I have a question, do you think that he would be interested in Programming if he was alive?

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Nutshell

I think he would want to know it, but wouldn't stick to it, he might use it as a tool to help him invent more things.

opengl15

The reason for this is you can be in space and running around the earth at high speed but that dont mean anything because the earth will still spin at its normal speed it allways has done. So its like a basketball spinning on the floor and your running around it really fast. that doesnt means the basketball is going to spin faster too. So all im saying it the earth will still be normal but if the earth was spinning really fast then that is something totally different.

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Shiro

>No the twin paradox was that from the Earth's point of view you
>have aged less, but from your point of view the earth has aged
>less.

Yes, that was what Nutshell said.

If I climb into my rocket on earth and launch myself and approach the speed of light, fly some day around in space and return back, then from my point of view, the time on earth went faster. From earth's point of view, my time went slower. Or: from my point of view, my time went slower and from earth's point of view, their time went faster. It's just which position you take.

>In reality if a person travels near the speed of light, they will
>age much slower then normal. So yes, planet of the apes (the
>original) is possible.

Normal? In relativity there is no "normal", since everything is relative.

And in reality a person can't travel near the speed of light, since his/her mass would become infinite. If you use Lorenz transformation to calculate the new mass

m = m0 / sqrt (1 - v^2/c^2)

then you can see that if your speed approaches c, then

v^2/c^2

will approach 1, so

1 - v^2/c^2

will approach 0, and

sqrt (1 - ~1)

will also approach 0 and dividing by a very small number is the same as multiplication with a very large number, so m would become really, almost infinite.

This is the theoretical part. Now the practical part. If I want to accelerate, then I need energy to do this. The amount of energy which is needed to accelerate depends on the mass. If the mass is almost infinite, then also the amount of energy is infinite. By the way, energy should come from somewhere. As discussed in a different thread, mass can be turned into energy. So I need to carry mass with me to turn it into energy.....

[EDIT]
This is how I remember it from university. If things are incorrect, or new research resulted in new theories, please correct me.
[/EDIT]

shtarker

>>then from my point of view, the time on earth went faster

No that is what the twins paradox is talking about. From the earth's frame of referance, the space ship is moving while they remain more or less stationary, causing the space ship to expirance time dilation.
However from the space ship's point of view it is the earth moving away from them, causing a time dialtion in the earth's frame of referance.
Relativity proves that both these observations are correct, thats where the paradox occurs.

xlnk

physics and programming can go together, you know...

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stevey

it is true according to Stephen Hawking and his book "a brief history of time". he's supposed to be one of the top brains arround, so it must be true !!!!
his next book "universe in a nutshell" is also good i'd recommend it.

heres a poser, light travels at light speed(obviously), and so it must have no mass, or as stated its mass would be infinite at that speed.
so why does gravity affect light (it bends it), if it has no mass ?????

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Steve

shtarker

Its all relative:
http://math.ucr.edu/home/baez/physic...oton_mass.html

stevey

thats a good link, i had read that on the other thread you replied on.
doesn't quite explain it for me though.
in fact the fact that gravity bends light is a poser for far greater brains than ours, since light has no measurable mass it shouldn't be affected by gravity.
the common explanation is that mass bends the space-time continuum, ie the classic ball sat on a 2d sheet thing.
but thats beyond me frankly.

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