Speed of Light: A universal Constant?
in [Relativity]
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From: G on 29 Apr 2005 04:34 BZ Thanks: will correct that. We know the spaceship will be seen to be going straight up from the asteriod - seen by all observers as going straight up, because the spaceship is carried along by the asteroid What about the light pulse / photon? What will it be seen to do for a moving observer? I just can't figure it out: we are in "space" with nothing to refer to .. except the stars? Given the effects will be very small for speeds very much less than c. Henri, I like to know your thoughts on this G G
From: G on 29 Apr 2005 05:02 The claim that light travels at 'c' wrt all observers is unsubstantiated and nonsensical Henri In AE's twisted universe, when you measure light , tiem and space dilates or shrinks to make the measured speed of light exactly c. It is measured by all observers as c "in their reference frame" . However this caused problems as I will show in due time See the wikipedia entry on speed of light "It is important to realise that the speed of light is not a "speed limit" in the conventional sense. An observer chasing a beam of light will measure it moving away from him at the same speed as a stationary observer. This leads to some unusual consequences for velocities" http://en.wikipedia.org/wiki/Speed_of_light G G
From: G on 29 Apr 2005 06:14 BZ I agree with your statement on doppler shifts. Why don't you do the experiment and c ? Sound is a good analogy to light where the observer is at rest WRT the medium of transmission. Using sonar (are they used to track speeding cars?) you will see relativistic effects for sound: cars will appear to contract in the direction of motion etc. Once again where the observer is at rest wrt to air, the analogy with light works because there are no medium - dependant effects: for light because it is not dependant on the medium, and for sound, the observer is stationary wrt to the air. Does the medium make a difference for the sound source? No because the speed of the source does not affect the speed of sound. What I am most interested in, and what is relevant is the pseed of the first photon emitted : when the beam of light first hits the target. Detecting individual photons is incredible: any experiments done on this: must search. Tell me , is it possible to detect c+v using a radar or lidar placed on , say a fast train moving at 300 kmh at a distance of say 3 km? What is the error margin? G
From: bz on 29 Apr 2005 06:11 "G" <gehan(a)dialog.lk> wrote in news:1114763673.568528.233850 @o13g2000cwo.googlegroups.com: > BZ > Thanks: will correct that. We know the spaceship will be seen to be > going straight > up from the asteriod - seen by all observers [on the asteroid] > as going straight up [assuming the asteroid is not rotating, things get much more complicated if it is rotating] > , > because > the spaceship is carried along by the asteroid > > What about the light pulse / photon? What will it be seen to do > for a moving observer? I just can't figure it out: we are in "space" > with > nothing to refer to .. except the stars? Given the effects will be very > small > for speeds very much less than c. > > Henri, I like to know your thoughts on this > > G > > G > -- bz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+nanae(a)ch100-5.chem.lsu.edu
From: bz on 29 Apr 2005 07:58
"G" <gehan(a)dialog.lk> wrote in news:1114769646.014073.265000 @o13g2000cwo.googlegroups.com: > BZ > > I agree with your statement on doppler shifts. Why don't you do the > experiment and > c ? I need to interest some people in getting the equipment together and running the experiment. > > Sound is a good analogy to light where the observer is at rest WRT the > medium of transmission. yes, to a limited extent. > Using sonar (are they used to track speeding > cars?) no. radar (radio direction and rangeing) and light radar (lidar) are used. > you will see relativistic effects for sound: cars will appear to > contract in the direction of motion etc. no. I don't think you can see relativistic effects (relative to the speed of sound). You CAN go faster than sound and mass does not increase as you approach the speed of sound. The analogy breaks down in many ways. > Once again where the observer is at rest wrt to air, the analogy with > light works because > there are no medium - dependant effects: for light because it is not > dependant on the medium, and for sound, the observer is stationary wrt > to the air. Does the medium make a difference for the sound source? the density of the media effects the speed of sound. Movement of the media effects the speed of sound. > No > because the speed of the source does not affect > the speed of sound. within limits, the speed of the source does NOT change the speed of sound. > > What I am most interested in, and what is relevant is the pseed of the > first photon emitted >: when the beam of light first hits the target. Detecting individual > photons is incredible: > any experiments done on this: must search. > > Tell me , is it possible to detect c+v using a radar or lidar placed on > , say a fast train > moving at 300 kmh at a distance of say 3 km? What is the error margin? first approximation light goes 300,000 km/s or 1.079e9 km/hr 300 km/hr divided by c = 2.79e-7 or so, IF doppler shift was all due to variation in speed of light. Light takes 1e-5 seconds to travel 3 km We need to be able to resolve a difference of (3*km/c)- (3*km/(c+300km/hr))=2.7e-12 seconds or 2.7 pico seconds. Since a train is difficult to control and reproduce, I want to use a spinning disk. I want to take an optical fiber from a laser mounted at the center of the disk and run it to the edge of the disk, there glue it so it launches the laser beam tangential to the edge of the wheel. I want to spin my wheel(in a vacuum) so that the source of the beam is going above the speed of sound in air. Say 600 km/hr. Spin the wheel the other way and you have -600 km/hr I then want to hit two detectors along a path and measure the time of flight of the photons between the two detectors. I expect to see over 1 ps difference over a 1 km path IF BaT is valid. -- bz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+sp(a)ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap |