Is lightspeed constant only to the observer?

Question

If time is relative to each observer traveling at different volocities and subject to different gavitational fields, and both observers measure the speed of light exactly the same using clocks that are running at entirely different speeds, isn't light in fact traveling at different speeds and constant only because it covers the same distance in relation to each observer's clock?

Answer 1

Light speed is a constant for all observers. As acceleration increases, both length and time are contracted (the Lorenz equations) equally, so that the speed of light is the same.

This was the very principle of Einstein's theory of special relativity.

Answer 2

Think about your question for a second. Yes light's speed is constant to an observer, but more importantly, the speed of light is constant to ANY observer! That is the point of relativity. From the viewpoint of one observer, the other observer's clocks and measuring stick will appear such that not only will they both think that they themselves measured the correct speed, but they will see the other observer measure the correct speed as well. There is no way around it, everybody will agree that the speed of light is the same and everybody will agree that everybody else measured it correctly! Amazing.
P.S. You ask if light's speed is constant only to the observer, let me ask you: Who else matters! All we have is observers, and if they ALL agree on a value for the speed of light, then that is the best we can do, that value IS the speed of light.

Answer 3

The speed of light is no longer constant, regardless of observers. It has been slowed down.

There is, of course, the question of light's speed from the perspective of light itself. If you were light traveling from the sun to the earth, you would get here instantly, whereas observers would see you get here in 9 minutes or so.

This is possible as light is both a particle and a wave... theoretically, particles propelled IN a wave.

But from the time dilation/contraction issues, we can gather that it is not the light that is wavy... but the rest of the universe =)


-D.

Answer 4

We measure the speed of light by measuring the distance it has covered in a particular interval of time.

The speed of light is measured as C by an observer who is not moving that is when he is at rest.

If a man moves with a speed of 0.8 C, then the length of objects in the direction of motion decreases by 0.6 times its original length. One meter reduces to 60 cm.
Similarly the time of one second becomes 0.6 second.

Consider how an observer at rest measures the speed of light. He finds the time taken by light to cover a distance of one meter. He measures the time as 3.3 nano second. Hence he concludes that the speed of light is 3x 10^8 m/s.

The man moving with the speed of 0.8C, also measures the speed of light.

He is not aware of the fact that in his frame the length of the meter scale is reduced and also that the time is going slow. Therefore, he will measure the time taken by the light to cover one meter as 3.3 nano second. Hence he concludes that the speed of light is 3x 10^8 m/s.

But we know that he is moving with a speed of light 0.8C. We know that the meter scale is now only 0.6m and the one second is now 0.6 s.

We will say that in his frame of reference, the light has taken 0.6 x 3.3 nano second to cover a distance of 0.6 x1m.

Therefore he measures the light’s speed as (0.6 x1) / (0.6 3.3 nano) {distance / time}
as 3x 10^8 m/s.

The amount by which the length and time decreases, depends upon the speed of the observer. But both length and time reduces by the same amount and hence the speed of light is measured constant.

Answer 5

Nope, time's speed is determined by two constants, therefore allowing no change in it.

Its strange to accept that for me too.

Answer 6

Let me mull this one over a bit, but I like the questions that make me think! Will you be my wife? lol