Existence

Except that it can't be independent of the car and the motion of the car, but somehow not independent of the salt flats and the motion of planet Earth, and not independent of the motion of the Sun though the galaxy, and not independent of the motion of the galaxy through the universe, and so on.What is so special about the car's reference frame that its motion is uniquely not imparted to the photon when it is created? Well, try this:

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Suppose you are moving toward something that is moving toward you. If you measure its speed, it will seem to be moving faster than if you were not moving. Now suppose you are moving away from something that is moving toward you. If you measure its speed again, it will seem to be moving more slowly. This is the idea of "relative speed."

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Before Einstein, scientists were trying to measure the "relative speed" of light. They were doing this by measuring the speed of starlight reaching the Earth. They expected that if the Earth were moving toward a star, the light from that star should seem faster than if the Earth were moving away from that star.

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They noticed that no matter who performed the experiments, where they were performed, or what starlight they used, the measured speed of light in a vacuum was always the same.[1]

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Einstein said this happens because there is something unexpected about distance and time. He thought that as the Earth moves through space, our clocks slow down (ever so slightly). Any clock used to measure the speed of light is off by exactly the right amount to make light seem to be moving at its regular speed. Mentally constructing a "light clock" allow us to see exactly how to explain this remarkable fact.

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Also, Einstein said that as the Earth moves through space, our measuring devices change length (ever so slightly). So, any measuring device used to measure the speed of light is off by exactly the right amount to make the starlight seem to be moving at its regular speed.

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Other scientists before Einstein had written about light seeming to go the same speed no matter how it was observed. The idea that made Einstein's relativity so revolutionary is that light does not just seem to go the same speed, it is always going the same speed no matter how an observer is moving.

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http://simple.wikipedia.org/wiki/Special_relativity

The connection is that an inertial observer - any inertial observer - will observe the speed of any light in any reference frame to be c. What says nothing? Please be specific. Which words? Please be specific.

ICANT,Have you ever ridden a train? Almost everyone who has, has had this experience: you're sitting there in your seat, waiting for the train to depart, and there's a train on the tracks right next to you. Slowly, you start to see the windows of the other train slowly slide past yours, and you think "oh, finally, we're on our way at last." You even feel the motion of the train under you and you sink into your seat a little deeper, it seems, as the train you're on accelerates towards the end of the platform - when suddenly, you pass the end of the other train and you see that you've not moved at all! It was the other train leaving and you've been stationary the whole time. Your sensation of movement was an illusion caused by your inaccurate interpretation of what you were seeing. You could only see that one train was in motion past another; you were not able to correctly determine which train was at rest relative to the station.That is why we say that driver observes the track moving past him; since motion is relative, that's identical to saying that the driver is moving past the tracks. The only difference in those statements is that they imply different reference frames. Taq's diagram and description of motion is accurate within the reference frame of the driver.

Because you could make observations of a third reference frame - the road and buildings around you, which you assume to be "stationary". That's an intelligence-based way to privilege a reference frame. But if you could not see those buildings and the road, you would have no way to determine if cars were driving past you, or you were driving past them, or some combination of the two. That's because there is no physics-based way to privilege a reference frame.When two cars pass each other, it's as equally correct to say that Car A passed Car B as it is to say that Car B passed Car A. There are no privileged reference frames. You've never had the experience, so you don't know. You'll just have to take my word that the illusion is so strong, you're made to feel the "acceleration" of the train even though the train is stationary. It's roughly the same effect as you might feel in a flight simulator, or more accessibly, one of those 3D video amusement park "rides" that don't actually go anywhere.If you've really never ridden on trains like this, or gone to an amusement park, your sheltered life is going to make it somewhat difficult to try to explain things to you since you won't have any of the obvious referents. Maybe you should stop posting here and get out more? That's just stupid. Distances are reciprocal - if A is a certain distance from B, B by definition must be the same distance from A. How could it be otherwise?You've clearly made an incredibly stupid blunder, here. Would you like to take it back and try again? No, it is exactly accurate in reality, which is why relativistic physics models are so adept at explaining reality, compared to your idiosyncratic "models" which would necessarily lead to being able to determine one's absolute location in the universe by means of a flashlight, which obviously nobody is able to do.

I think ICANT believes that a force is acting on a constant-velocity, moving car because it is moving; that is, ICANT has Aristotle's understanding of motion where force is necessary to maintain motion.In other words most of ICANT's problems here come from the fact, as you've identified previously, that ICANT rejects not only relativistic physics, but Newtonian physics as well. The rest of us understand that there is no net force acting on the car because it is not accelerating.

I have not made any claim that it was. You mean to say that the laser emitter is mounted transverse to the axis of travel. Yes, I think everyone understands that (but you, apparently.) But the car is not the only thing moving .5c in that direction. The laser pen has the same velocity (as measured from the same reference frame) and, as a consequence, the velocity of the laser light being emitted from it has a vector projection on the axis of travel of .5c as well.That's not saying that the velocity of light is .5c; that's saying that if you considered only the vector component of the light's velocity in the axis of the car's motion, it would be .5c. That is why, in the reference frame of the car, the laser light travels exactly transverse to the axis of motion of the car. No, of course not. But the motion vector of the car is a component of the motion vector of the light. That is why the laser in the car hits precisely what it is aimed at, it doesn't veer off towards the rear of the car. If that was ever the case we could all violate relativity at will and determine our absolute velocity anywhere in the universe by means of flashlights, which clearly nobody is able to do. It's not necessary to add a force to the light; it's already going in exactly that direction. No, exactly wrong. The solution is that the laser pen is mounted transverse to the axis of the car's motion across the salt flat.

Firstly 3LoT states that the entropy of a pure, perfect crystal at zero kelvin is zero, not anything about perpetual motion machines. Secondly, we're assuming a frictionless car because that's a common simplification made in physics problems. Everybody knows what friction does - it turns kinetic energy into heat. (As it happens, it doesn't matter - the second law disallows even frictionless perpetual motion machines.)Thirdly there's nothing to "size up"; a body in simple constant motion in an empty universe isn't a "machine" in any thermodynamic sense.

We can certainly say that it is stationary relative to its own reference frame. Nothing is ever moving relative to itself. Sure, but it has zero velocity relative to itself. Further, since it has constant speed it is being acted on by no forces. Since no forces are acting on the light beam either, we know that the light beam will hit the detector, because in that frame of reference the only thing with motion is the light beam and we know what direction it is pointed. Relative to the emitter, the car will not move any distance whatsoever. Except to itself.

No, because the "point at which the photon was emitted" is also in motion, along with the car.

Because it is a point in a moving reference frame. Since the coordinate system is in motion, and since the definition of the location of a "point" is relative to a coordinate origin, the point is in motion.If I draw a point at 2,3 on a piece of graph paper, and then I pick up the paper and carry it across the room, I've defined a moving coordinate system and everything at rest in that system shares it's velocity. The point is in motion throughout the room. The "mechanism" is the moving coordinate system, in which the point has been defined.

Well, no. That's not what Postulate #2 says. Otherwise it would be impossible to control the direction of light, use mirrors to reflect it or lenses to bend it, etc.Postulate 2 merely states what we've been telling you throughout - your own velocity is irrelevant when you attempt to measure the speed of light. Regardless of your direction of travel or speed, when you measure the speed of light in a vacuum, it will be C. That's why the postulate is called "the invariance of C." That's a statement about the magnitude of the velocity vector of light, not its direction.

And the photon will travel at the same direction that the laser pen is pointed when the photon is emitted. When the photon strikes the road, the detector will be pointed at exactly the detector that the photon will hit.Remember that even at time=0 in this setup, the emitter is in motion. You've defined its velocity as constant. If instead the car was at rest, emitted a photon, and then accelerated to .5c, the photon would hit the detector the emitter was pointed at when the car was at rest. It has to - no forces can act on the photon after it is emitted in this setup.But the car is already moving when the photon is emitted; thus, the photon's velocity vector has the car's constant motion as a component. The most convenient way to deal with that component is to consider the photon's motion in the reference frame of the car where everything attached to the car has that velocity component and thus we can cancel it out. In the reference frame of the car, everything that wasn't attached to the car or emitted from the car has the reciprocal velocity, and that's just the track.Thus, mathematically, the photon hits the second detector because, after the photon was released from the car, the detectors were all moving towards the rear of the car at .5c Since no "unbalanced force" acts on the photon, its path cannot deviate, and thus it cannot hit the first detector which is no longer where it was when the photon was emitted and pointed at it.

In summary I'll only remind participants that the experiment of the photon and the moving car has already been performed, it's called the "Michaelson-Morley experiment". It specifically tested the trajectories of photons in a moving reference frame - the Earth's motion through space - and while most people, including the experimenters, expected that the paths of the photons would deviate relative to the apparatus as a result of Earth's motion, in over a hundred trials they did not even once observe this. Note that the apparatus used interferometry so a deviation of even a small fraction of the wavelength of light - a distance of a handful of nanometers - would have been detected. No such deviation was ever detected.This was in 1886. ICANT and his hand-picked cranks have yet to catch up to physics that is over a hundred years old. We do live in a universe where special relativity is true; the experiment that proved it has been repeated over and over again with the same result. Despite having been reminded of this perhaps two dozen times, ICANT did not at any time respond to this simple and elegant proof of SR which has withstood the test of time.