i still dont understand how someone can "escape"time by traveling faster than light.

[cameron marical]

if ive read and watched correctly, einstein concluded that you can esseintelly travel back in time, or at least ''escape'' it, by travelling at the speed of light. how? i watched a thing on the history channel were there was an astrounaught on there, who had a twin brother, and when he went in to space, he went so fast that he is now actually like .511 seconds younger than his brother now. how? can anyone help me out here?

[NowThatWeKnow]

Actually, only electromagnetic radiation (like light and radio waves) can move at the speed of light because the photon has 0 mass. All matter is restricted to speeds below this. This short power point presentation may help you understand time dilation.

http://faraday.physics.utoronto.ca/PVB/Harrison/SpecRel/Flash/TimeDilation.html

 

Also my thread in "relativity" "1G relativistic rocket ride Wheee" gets into it a lot.

[swansont]

Traveling faster than c violates causality — it's possible to get information about the outcome of an event before the event occurs, e.g. the push of a button, which means you could decide not to push the button.

 

The scenario with the astronauts is known as the Twins Paradox. It's not traveling back in time, but deals with relativity and the notion that time depends on your frame of reference (i.e. it goes at different rates in different reference frames) rather than being universal

[NowThatWeKnow]

The twin paradox: Is the symmetry of time dilation paradoxical?

http://www.phys.unsw.edu.au/einsteinlight/jw/module4_twin_paradox.htm

[cameron marical]

why cant something with mass go the speed of light? in space theres no friction, so theres nothing to stop it, ya, itd take alot of energy to get it going that fast, but i dont see why its impossible. like if you shot a gun, out of a bigger gun, and the gun shot would shoot out another gun, and they all shoot at the same velocity,just doubled of course, then the second gun shot would be twice as fast as the last. do this over and over again, itd take a while, but once your in the high numbers, itll take less and less every time{obviously}. so you might be able to then get to the speed of light. if so, then what would happen if you shot one more time? would it do the same thing as a photon would do, continue accelerating at the speed of light from wich it was sent, or, since it does have mass, would it go twice as fast as the speed of light? what would be the time like on board? and off board to people on earth{assuming the guns were spaceships, and in space}

[iNow]

why cant something with mass go the speed of light?

The faster you accelerate, the more massive you become. The more massive you become, the more energy it takes to accelerate further. As you approach the speed of light you become so massive that the energy required to accelerate you more is infinite (to keep accelerating, it would take more energy than is contained in the entire universe). The speed of light can only be attained by massless objects... i.e. Light itself.

[Janus]

like if you shot a gun, out of a bigger gun, and the gun shot would shoot out another gun, and they all shoot at the same velocity,just doubled of course, then the second gun shot would be twice as fast as the last. do this over and over again, itd take a while, but once your in the high numbers, itll take less and less every time{obviously}. so you might be able to then get to the speed of light. if so, then what would happen if you shot one more time? would it do the same thing as a photon would do, continue accelerating at the speed of light from wich it was sent, or, since it does have mass, would it go twice as fast as the speed of light? what would be the time like on board? and off board to people on earth{assuming the guns were spaceships, and in space}

 

The problem is that velocities don't add up like that.

 

For instance, assuming that the velocity of the second gun was "u" and the velocity that it fires the third gun out is "v", then the velocity that the third gun relative to the first gun won't be:

 

u+v

 

but

 

(u+v)/(1+uv/c²)

 

so if u is 0.5c and v is 0.5c then they add up to

 

0.8c not 1c

 

0.8c and 0.8c add up to

 

0.9756c

 

0.9756c and 0.9756c add up to

 

0.9997 c

 

etc.

 

The sum will never add up to c

[cameron marical]

well that sucks. are there any other theorys on "lightspeed" acheivment?

[NowThatWeKnow]

Do a google search for "faster then light speed" and you get all sorts of stuff.