twice of the speed of light???

[Moontanman]

All this talk about the view point of the observer and the observed has made me think of what a person actually traveling near the speed of light would see as their own speed. It seems to me if a person traveling close enough to the speed of light to have a time dilation of 1/10 would see themselves as traveling ten times the speed of light. At the very least their experience of the trip would seem to be faster than light, ten light years in one year.....

[Janus]

Originally Posted by Moontanman

All this talk about the view point of the observer and the observed has made me think of what a person actually traveling near the speed of light would see as their own speed. It seems to me if a person traveling close enough to the speed of light to have a time dilation of 1/10 would see themselves as traveling ten times the speed of light. At the very least their experience of the trip would seem to be faster than light, ten light years in one year.....

Actually, they would see themselves moving at 0.995 times the speed of light. The reason they make the trip in 1 year by their clock is because, due to length contraction, the distance has shrunk to 1 light year from their perspective.

[Moontanman]

Originally Posted by Janus

Actually, they would see themselves moving at 0.995 times the speed of light. The reason they make the trip in 1 year by their clock is because, due to length contraction, the distance has shrunk to 1 light year from their perspective.

I understand the whole length contraction but they wouldn't be able to see that contraction would they? To them it should be like they are traveling faster than light, or is it both? Or neither?

[Janus]

Originally Posted by Moontanman

I understand the whole length contraction but they wouldn't be able to see that contraction would they?

Why not? Imagine there is a measuring tape stretching across that 10 ly distance marked off in meters. They fly along side it. They take a "snapshot" of one of the meter marks as they pass and compare them to a meter stick they have on board. They note that the "meter" marks on the tape are only spaced 1/10 of meter apart according to their stick. They count the number of marks they pass, divide by ten and get a number of meters traveled equal to 1 ly.

[Elena]

I have a question...
If you were in a car travelling at the speed of lightand then you turn the carlights on, would you see them?
I got this question from a comedian and was thinking this is actually a good question, and so was wandering if there was an answer.

[Moontanman]

Originally Posted by Elena

I have a question...
If you were in a car travelling at the speed of lightand then you turn the carlights on, would you see them?
I got this question from a comedian and was thinking this is actually a good question, and so was wandering if there was an answer.

Well, since a material object cannot travel at the speed of light lets say the car was traveling at .999999% of the speed of light. From the occupant of the car's point of view the head lights would shine just like they would at regular speed.

[CraigD]

Originally Posted by Janus

Actually, they would see themselves moving at 0.995 times the speed of light. The reason they make the trip in 1 year by their clock is because, due to length contraction, the distance has shrunk to 1 light year from their perspective.

Relativistic length contraction gets really fun when you consider that, from the point of view of an observer watching the fast moving spaceship or whatever, it is the length of the ship, not the distance it is traversing, that is contracted, leading to weird, but entirely explicable thought experiments like the ladder paradox. This thought experiment provides a great illustration of another important feature of special relativity: not only clocks and yardsticks, but simultaneity, too, is relative.