Why does time stop when we travel at the speed of light?

In summary, time always continues the same when someone travels at the speed of light. Mass doesn't increase at the speed of light, and if you have mass, you can't get to the speed of light. The energy problem also applies.
  • #1
benzun_1999
260
0
dear reader,
Why does time stop when we travel at the speed of light?

Why does mass increase when we travel at the speed of light?

-benzun
 
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  • #2
For you, time always continues the same.

Mass doesn't increase at the speed of light. If you have mass, you can't get there!
 
  • #3
Basically, you are asking people to explain special relativity.

There have been whole books written on the subject!

In very rough terms, the problem is this:

Galileo, long ago, postulated that motion was "relative"- that is, that if you were in an enclosed cart, moving along a very smooth road at a constant velocity, there is no experiment you could perform that would tell you how fast you were moving (or if you were moving at all)- that is, that speed MUST be "relative to" some outside position.
Basically this is because of "f= ma": force, which is really how we "feel" the world depends on acceleration, not speed.

In the 19th century, it was discovered that a moving electron can be affected by a magnet depending on the speed of the electron (Galileo,of course, couldn't do electromagnetic experiments!). That meant that one could theoretically do some kind of electromagnetic experiment to determine an "absolute" speed.

In the late 19th century, Michaelson and Morley did exactly such an experiment using light (electromagnetic waves). They got a "null" result- their experiment showed no change no matter how they positioned their apparatus- there was no "absolute" speed. This is probably one of the most repeated experiments in history (certainly for one that reaches a null result) and always with the same result: there is no "absolute speed".

Lorentz suggested that perhaps the change in electromagnetic force in the direction of motion contracted the arm of the apparatus in that direction just enough to give an apparent null result (the kind of trick nature plays on us all the time!) and calculated what that contraction must be: l'= l sqrt (1- v2/c)

Other experiments showed that it can't be the electrons in the arm of the apparatus that do the contracting but Einstein made the extreme suggestion that it was space itself that contracted! The formulas are exactly the same as Lorentz (since they were derived directly from the Michaelson-Morley experiment) but Einstein showed that the contraction of space also implied that mass must increase:
m'= m/sqrt(1-v2/c), and time itself slow down
t'= tv2/c).

If you put v= c in those formulas, you will find that the length becomes 0, mass becomes infinite, and the time interval becomes 0.

Those are reasons why a body with mass CANNOT move at the speed of light!
 
  • #4
Nicely put.
There is also the energy problem. As your velocity increases, so does your mass, so you put in more energy and get another mass increase as well as a velocity increase. It ends up like the law of diminishing returns. You would need infinite Energy to accelerate any mass up to the speed of light (if of course it were possible in the first place, which it isn't!)
 
  • #5
t'= tv2/c)

This was supposed to be "t'= t(1-v2/c2" but got butchered!
 
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1. Why does time stop when we travel at the speed of light?

According to Einstein's theory of relativity, time is relative and can be affected by factors such as gravity and velocity. When an object travels at the speed of light, it experiences infinite time dilation, meaning time appears to stop for the object.

2. How does traveling at the speed of light affect time?

Traveling at the speed of light causes time to move slower for the object in motion compared to a stationary observer. This is due to the fact that the faster an object moves, the more energy it requires, and this energy is used to counteract the effects of time dilation.

3. Can time really stop?

Time stopping completely is a theoretical concept that is only applicable to objects traveling at the speed of light. In reality, no object can achieve the speed of light, so time cannot completely stop for any real object.

4. What is the significance of time stopping at the speed of light?

The concept of time stopping at the speed of light helps to explain the behavior of light and other particles that travel at this speed. It also plays a crucial role in understanding the concept of spacetime and how it is affected by gravity and velocity.

5. Can we travel back in time by traveling at the speed of light?

No, traveling at the speed of light does not allow us to travel back in time. It only affects the rate at which time passes for the object in motion. Time travel is still a theoretical concept and has not been proven to be possible.

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