If you take a laser pointer and point it at the moon and move the laser pointer fast enough across the face of the moon, wouldn't you be able to get the point of light shown on the moon to travel faster than the speed of light across the moon given the distance the moon is from Earth and the time it would take to flick your wrist?
2007-07-11 11:38:52 · 10 answers · asked by Anonymous in Science & Mathematics ➔ Physics
There are various phenomena that travel faster than the sped of light or c, but are not violations. You named one. The laser spot can move faster than c.
There are others. Suppose a wave hits a beach at an angle. The point at which the wave hits the beach has a velocity depending on the speed of the wave and its angle to the beach. As the wave becomes more parallel to the beach the speed increases. If the wave is exactly parallel to the beach, its speed is infinite, so what.
In the early days of radio, engineers discovered radio waves bouncing off the ionosphere. When they realized the waves were not actually bouncing but refracting they had a problem. The radio waves were already traveling at the speed of light. In order for them to refract, part of the wave has to travel faster than c. Finally it was discovered that the group velocity (the part of the wave that carries information) still wasn't traveling faster than light, only the phase velocity.
So, can anything real ever travel faster than light? Some subatomic particles can travel faster than light can in some mediums like water. When they do, they give off radiation known as Cerenkov radiation which slows the particle.
If you were falling into a black hole, at the point you reach the event horizon, as far as you could tell, you would be traveling at the speed of light. How fast would you be falling once inside the black hole. There are differing opinions about that, but I believe that to you, all the physics experiments you could perform would indicate you were traveling faster than c.
2007-07-11 16:37:44 · answer #1 · answered by jgreimer@sbcglobal.net 2 · 3⤊ 0⤋
Yes, the point of light can travel arbitrarily fast.
However, the point is just the intersection of a beam (a stream of photons) with the surface of the moon. There is no individual particle that travels faster than the speed of light.
This is not just "legalism": The point about the upper limit being c is that you can't communicate a signal faster than the speed of light. And even though the light spot travels from point 1 to point 2 arbitrarily fast, this is not controlled by anyone on the moon, so this is not a signal. (If you make the axis of flicking your wrist controllable by someone on the moon, you have to include the time to signal from the moon to your wrist as part of the signal time. You then lose whatever you thought you had gained.)
2007-07-11 20:59:59 · answer #2 · answered by ? 6 · 1⤊ 0⤋
The light is moving from the laser pointer to the moon. The light isn't actually traveling across the surface of the moon. Think of the light beam as a stream of photons (or even ping pong balls).
2007-07-11 18:42:37 · answer #3 · answered by Intrepyd 5 · 3⤊ 0⤋
Once the laser pointer is pointed at the moon and you move it, it would take time for the light to reach the new part of the moon you're pointing it at.
Just like the person above said, imagine a turning while holding a flame thrower. The flame lags where you change direction to.
2007-07-11 18:44:46 · answer #4 · answered by schlouey 3 · 1⤊ 1⤋
the lazer moves at the speed of light, and nothing more. There is no possible way to auctually 'see' it hit the moon, because the laser would spread too much, and not even be visible any more. Its hard to get a laser to show up 100 yards away, let alone a million miles
2007-07-11 18:49:37 · answer #5 · answered by God! 1 · 0⤊ 1⤋
If you are able to out-smart relativity, then by formal logical hyper math
if a zerba has stripes
if stripes are black
zerbas have black stripes
you, therefore are smarter than einstein.
I'm afraid but your logic is flawed. If you wish to make the assertion that you have outsmarted einstein, then please create a msypace account.
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Yahoo answers does not gain any value, when people dilute this encyclopedia of forthrightitude with trivial christianity.
2007-07-11 21:42:26 · answer #6 · answered by Voltaire's book Candide 3 · 0⤊ 0⤋
No. If you did that, and could see the point on the moon, you could measure the lag time and find that it is in keeping with the speed of light.
2007-07-11 18:48:08 · answer #7 · answered by Anonymous · 0⤊ 1⤋
Just because the spot can move at superluminal speed does not mean that light can travel at superluminal speed. The light travels from the pointer to the moon. Nothing is traveling with the spot.
2007-07-11 18:53:03 · answer #8 · answered by Anonymous · 4⤊ 2⤋
Yes. But an image is not an actual object, so it cannot transfer information. So it does not violate relativity.
2007-07-11 18:41:21 · answer #9 · answered by SAN 5 · 3⤊ 0⤋
Yes, but nothing physical or carrying information is really exceeding 'C`.
2007-07-11 18:43:53 · answer #10 · answered by Irv S 7 · 3⤊ 0⤋