if you travel at the speed of light?

Question

if you travel at the speed of light to proxima centauri, and it takes 4.2 light years. and in theory at the speed of light, time stops. so why dose it take 4.2 years (in time) to get there?

we can measure the time it takes at the speed of light (186,000 miles per second)from point A to B, but for the traveler time stops. why?

Answer 1

4.2 Earth years. The theory is, time would seem to stand still for the traveler and the jouney would appear to occur in the blink of an eye. Since no one has tested it conclusively, it is still a theory, relatively.

Now it takes roughly 8.5 mins for light to reach us from the Sun . . . but since light travels at the speed of light (duh) why doesn't it get here instantaneously? Maybe to the light particle, it was instantaneous. Wahoo!

Get it?
Have fun and keep thinking!

Answer 2

Because time is relative, not absolute. That is what relativity is all about. Time slows down for people traveling at high speeds, and if people could travel at light speed (which they can't), time would stop FOR THEM. But back on Earth time goes on normally. So the people go to Proxima Centauri at the speed of light (which they can't really do, but just hypothetically, if they did), visit for 1 day and return to Earth. They think they were only gone 1 day but people on Earth are 8.4 years plus 1 day older when they get back.

Why? You can ask that question forever, like a 2 year old, and not get an answer. But it is a requirement for the speed of light to always be the same, and the fact that the speed of light is always the same is proven by experiment. So is slowing time. Unstable subatomic particles are able to exist longer than they should in particle accelerators because time has slowed down for them.

Answer 3

This is not that hard to understand.. if a person is traveling at the speed of light and it takes light 4.2 years to get from point a to point b then it will take that long for the person to get to point b also.. time stops for the traveler because all the human measurments are set according to the speed of light.. 4.2 years is still 4.2 years regardless of how fast you travel.. here is an example of how time seems to slow down to space travelers.. If the wind were blowing at 40 miles an hour from the South and you were to go up in a hot air baloon.. you would not feel the wind.. why?.. it is simple.. you would not feel the wind because there would be no resistance.. you would be traveling at the speed of the wind and it would feel as though you were not moving.. the only way you could be able to tell that you were moving would be for you to focus in on a fixed object on the ground.. and you could measure from point a to point b to see how fast you were moving.. if you had nothing to focus on then you would think that time is standing still..

Answer 4

Firstly, it takes 4.2 *relative* light-years (LY). By relative, I mean 4.2 LY from an observer's perspective who is not affected by the traveler's speed. This is the basic premise of Einstein's theory of relativity. So, if hypothetically we had *instant* communication between Earth and Proxima Centauri, reports would say that the traveler should arrive to his destination in 4.2 years, however, he would have aged less than 4.2 years.

Secondly, time probably does not stop at the speed of light. Speed and gravity have been shown to warp time but not to the point of actually stopping it. Time will in fact slow by minutia for the traveler at light's speed, however, it will not stop.


btw the premise that humans cannot travel at/ or obtain light speed is highly debatable.

Answer 5

When you travel at the speed of light time stops for the traveler but not for the rest of us. It would take you no time at all to travel anywhere at the speed of light but time would still pass for the rest of us.

The reason for this is, well, the equation for this is: time for the traveler equals time for us divided by the square root of 1 – the ratio of your speed squared and the speed of light squared. This means that the closer you get to the speed of light the closer that ratio gets to one. As you know, one minus one is zero and you cannot divide by zero and get a meaningful answer. This is why you cannot actually go at the speed of light.

But, you do not have to. You could go at, say 80% of the speed of light so a ten year trip for us on earth would take you only 7.5 years. Or you could go at 99% the speed of light. Well, at least in theory.

This is called “time dilation” and it is, as the first answer says, due to relativity. Whenever you travel through space you also travel through time. The rate at which you travel through space is calculated by using the equation v = d / t. When you travel through time the equation is a little more complicated. But, make not mistake, the faster you travel through space the slower you travel through time.

The actual effects of this are not noticed until you travel at very large speeds. Speeds that are attained by the satellites that transmit your cell phone calls or your GPS system in your car, or even the electrons that travel in your TV or computer CRT. If the engineers who designed these systems did not take into account that time really does slow down for the electrons that transmit the information in your TV/computer CRT they would not work. They must also take relativity into account in the GPS systems and in our cell phone systems or they, too, would not work.

Answer 6

We can't compare light itself to objects like spaceships. Spaceships have mass but photons of light have no mass. They *do* have a kind of rest mass, but under normal circumstances photons of light are never at rest, so no mass.

If we could accelerate a spaceship--something with mass-- up to, say, 90% the speed of light time aboard the spaceship would move along at the *same* rate as usual. However, and here's the tricky part, if someone left behind stationary with respect to the spaceship could watch a clock on the spaceship it would show that relative to them time is moving more slowly.

Answer 7

Relativity dictates that as you approach the speed of light, time slows down.

For someone observing the traveler, time doesn't slow down.

If you want to understand WHY that is so, check the link below (but be prepared to take some college courses first :))

Answer 8

There were so many good answers.
I would like to mention 'john t's answer was that it gave general relativity theory as an answer. No, it would be special relativity theory.
'Quantum P' was correct, your clock is tick,tick, and tick. To you, it records time honestly. But to an observer outside traveler's reference frame, these tick, tick, tick seems slower. It took longer than one second for another tick to occur.
Probe A and Probe B were two experiments conducted to prove the relativity theory.(Stanford University, physics dept.)

Answer 9

Motion through time multiplied by motion through space = c [or the speed of light]. So, the faster you go through space, the slower you go through time relative to an observer outside your frame of reference. Even though your watch would still tick off a second and another and another, etc accurately from your point of view, it would be ticking more slowly from the viewpoint of someone outside your frame of reference.

Answer 10

1) time stops for the traveler RELATIVE to the observer.
2)Probably because the normal energy state changes occur at a slower rate if at all. ( I have not found anyone who can explain it any better or at all so far.......)