Wouldn’t time dilation govern a speed limit?

Swerdna, you're completely correct... but note that dilations happen BECAUSE of the speed limit, not the other-way around.

 

Dilation starts effecting things at any velocity. The effects are very small until you get close to C. This is the factor by which things are dilated (time and space):
http://en.wikipedia.org/wiki/Lorentz_factor
Graph it on your calculator with C = 1; as V -> 1 (becomes the same as C), the lorentz factor approaches infinity; thats the speed limit.

I'm not sure what math level you're at, but the derivation for that formula isn't too complicated - you just have to assume that the speed of light is constant, then do some clever geometry, i think the wikipedia article links to a derivation.

 

Time dilation only takes effect on objects that are moving relative to the observer. A stationary observer will see no effect on the clock because the clock is not moving relative to the observer, regardless of how fast it is moving relative to anything else.

 

I think time dilation of accelertion is slightly better picture. Say you have a missile that is capable of accelerating to 0.8c before it burns up all its fuel. Say the missile is placed on a mother ship that accelerates to a speed of 0.8c relative to you before firing the missile. When the missile is fired from the mother ship the fuel is burned up slowly due to time dilation and the missile accelerates much more slowly and only reaches a top speed of about0.976c relative to you or 0.176c faster than the ship it was fired from.

The equation used to calculate the additive speed (0.976) is the relativistic velocity addition equation v = (u+w)/(1+u/c*w/c) where u is the velocity of the ship and w is the velocity of the missile.


Earlier you asked "if you reached the speed of light would you stop due to time dilation?". It would be slightly better to say that as you aproach the speed of light relative to another observer your acceleration relative to the other observer tends towards to zero no matter how much fuel you burn up. Of course, to you onboard the ship it would look like you were always accelerating at the same rate and your onboard accelerometer would indicate that. However, because no physical object can get exactly to the speed of light your relative acceleration would never reach exactly zero.

 

i posted this in another forum but want feed back please help, and thx for your time! I've been told that as a person approaches the speed of light, time relative to others being viewed slows. when you make the speed of light ( if possible, I’m aware of distance change and mass increase and of the immense amount of energy needed to possibly reach this speed to push that mass) time for others stops and past the speed of light time goes back wards. Does this huge mass increase make an objects gravitational force so immense that it drops through space time and can continue traveling at higher speeds then light? Such could be possible in the even of a star becoming too heavy and dropping through space time to create a black hole. BUT what happens as you slow down? As in all the particles in your body slow down to absolute zero, where your temperature and kinetic motion would be zero. Would this result in forward time travel? Does mass decrease?

 

Hi Campal,
you've been told wrong. All motion is relative, and there's no absolute velocity. So it does not make sense to say ' as a person approaches the speed of light' unless you say who is measuring them. Relative to someone in a distant galaxy you may be travelling at a huge velocity, but it makes no difference to you, you are stationary in your own frame.

M

 

THE OBSERVER IS TRAVELING AT LIGHT SPEED WATCHING A SYSTEM TRAVELING AT SPEEDS WE NORMALLY TRAVEL AT. but if you alter the E+MC(^2) EQUATION and sub in the rate of time won't you find that as velocity increases to the constant of "c" (the speed of light), the rate of time pasage (for others, not moving at your speed) decreases and if light speed was acheived their time would no longer pass, and if you passed the speed of light their time relative to you would go backwards?

 

If you imagine a particle traveling at twice the speed of light its time dilation factor would be [tex]1/\sqrt{(1-v^2/c^2)} =1/\sqrt{(1-(2c)^2/c^2)} = 1/\sqrt{-3}[/tex]

The square root of a negative number is an imaginary number. That tells you are not looking at a real physical situation. We can only "imagine" it. Some mathematical models in physics involve intermediate imaginary numbers in the calculations, but they only have physical significance if the imaginary parts cancel out and a real answer is obtained.