Existence

The detector has not moved in the driver's reference frame. It's velocity is zero in that reference frame. You are the one adding the velocity of the Salt Lake Flats to the velocity of the light, causing it to curve backwards. This is a violation of postulate #2 by your own criteria.

The driver

Hi ICANT, You don't know what you are talking about. Perhaps you should do some research into how lasers emit pulses of light. I warned you that the details mattered mattered, but you still spouted off some nonsense about how laser pens work without looking it up. I'm not doing the homework for you because it does not matter to the discussion.But here's a clue. No, a laser diode does not work by turning electrons into photons. When electrons leave the battery an equal number of electrons return to the battery. Instead the potential energy of the electrons leaving the battery is used to generate light and lower energy electrons are returned to the battery.Is this really something you'd choose to argue with an electrical engineer about? I suppose it is a little better than insisting that positrons are involved.

To the pen laser and observer. They are all in the same inertial frame of reference. The velocity at which the Salt Lake Flats is speeding by is irrelevant to the calculation since none of the pieces are in the Salt Lake Flat's inertial frame. The driver will observe the light pulse hit the detector with no deviation no matter what the relative velocity is between the driver and Salt Lake Flats.

Hi Taq, I can agree the car with the laser pen and pole attached to it are not moving distance relative to the driver.The problem is when the pulse is created and released external to the car the pulse is traveling at c relative to the laser pen where it was emitted and will travel in a straight line from that point.Also since the car is traveling at 0.5 c horizontaly relative to the Salt Lake Flats and the Pulse is traveling at zero horizontaly to the Salt Lake Flats and is traveling c verticle at a 90 angle relative to the Salt Lake Flats the pulse will miss the detector.God Bless,

ICAN'T,Let's add a treadmill to the mix. We will put this huge treadmill on the Salt Lake Flats and under the car. We then rev it up to 0.5c so that the treadmill is rushing by the car at 0.5c. So what does the driver observe now? Does the pen laser hit the detector dead on, or does the light take on the velocity of the treadmill rushing by at 0.5c and violate postulate #2 in the same way that you insist it does for the Salt Lake Flats?

Um...but you said... Message 847How can this be when now you say... Which is it?? You cant have it both ways??

Then their velocity is zero, not 0.5c. The observer's reference frame does not stop at the car. It extends to infinity in every direction. In this reference frame the pen laser and detector have zero velocity. This is where you are making the mistake. Mark the point on the Salt Lake Flats 90 degrees below the pen laser at the time point where the light pulse starts. Now draw a line from that same point to the position of the detector when the light pulse hits it. That angle is not 90 degrees. That is where you are making the mistake.Added by edit:Let's also make another observation. Instead of firing the laser at a target above the car, let's fire the laser at the Salt Lake Flats. So, fire the laser down and mark the spot on the Salt Lake Flats where the laser hits. Measure the angle between that point and the position of the detector at that instant. It should be a 90 degree angle, should it not? The point on the Salt Lake Flats where the laser strikes should be directly below the detector, should it not?Edited by Taq, : No reason given.

Hi ICANT, Then you assume wrong. I prepared them during the time I prepared the text for the post the drawings appear in.Further, I have no idea what causes your confusion. There aren't any mirrors in the drawings. The only thing present in the drawings are sets of coordinate axes and photons. No ICANT. There are no photons or photon paths depicted in that picture. The only thing pictured in the A/B illustration are the x and y coordinate axes (with labels) for two different reference frames. The diagrams are perfectly well described in the text. Your comments and objections to the drawings make absolutely no sense. Edited by NoNukes, : No reason given.Edited by NoNukes, : No reason given.

Nicely said. This is exactly the point I attempted to make with those coordinate system drawings.Intentionally or not, ICANT is espousing some version of an aether theory in which the salt flats frame or whatever local earth point is involved is absolutely determining of what constitutes zero velocity. We know from experiment that this isn't how things work in our universe without marmalade skies and girls with kaleidoscope eyes.Physics works the same in all inertial reference frames. There are no inertial frames in which a light beam directed vertically in that frame by an observer at rest in that frame travels backwards.And how does ICANT justify his position? By reading postulate #2 without having an understanding of what an inertial reference frame is. Because he does not understand that, he cannot understand what it means to measure the speed of light in a vacuum in any inertial reference frame.

Not exactly,Length contraction does affect what that different angle is, but the angles would be different even without the SR effects. The difference in angles for the path of a light beam as observed in different reference frames is due to the speed of light not being infinite. The effect is present even under a newtonian/galilean coordinate transform and applies to the path of any object.The universality of this principle is one of the things that makes ICANTs rejection of it more difficult to understand; until you realize that ICANT does not understand inertial coordinate systems. Your remarks in Message 908 capture the principle perfectly.

Yeah, you are right. The more I thought about it the wronger (hehe) it sounded.

I brought this up as well. This is why I used a treadmill in one of my thought experiments. For some reason, ICAN'T thinks that there is something special about the Earth's reference frame, as if the whole universe has adopted the Earth's reference frame in order to determine where light goes. It gets even wierder when talks of reference frames being within other reference frames.From my own personal experience I know that there was a "lightbulb" moment when relativity made sense. I think that ICAN'T is purposefully avoiding situations where this lightbulb could be turned on. I have seen it happen with other topics as well. It's like leading a horse to water only to have it run away just as its nose is about to touch the water. Completely agree.

The photon doesn't miss the target.If the vehicle and apparatus was accelerating, you would be correct, and the photon would miss the target (towards the back of the vehicle).
If the vehicle and apparatus was deccelerating, you would be correct, and the photon would miss the target (towards the front of the vehicle).
However, the vehicle and appartus are not accelerating (either positive or negative)... therefore, the photon hits the target dead-centre.If you were right, if the photon actually missed the target (towards the back of the vehicle), only under velocity and no acceleration/decceleration... then can you understand that this would cause the photon to actually hit the target if the vehicle was under a certain amount of decceleration??Can you understand that this makes no sense at all?
Think of it... you're in a car, moving forward at a constant speed, you toss an apple in the air... all of a sudden the brakes slam on... and the apple doesn't slam into the windshield??? You actually catch it just fine in your hand again? Are you serious?You're not even wrong about a complicated aspect of physics. You're wrong about the simple parts...
Light is not different from anything else in this simple aspect... it's different in the difficult areas that you're just surrounding the example with to make it seem like you're arguing a "higher level" point... but you're not... you're wrong and arguing about the simple physics point that is very basic.It's just so simply shown to be a wrong way of thinking about the reality of physics...

Why is the Salt Lake Flats reference frame so special that it should intrude on the car's reference frame?What about the fact that the Salt Lake Flats is located on Earth, which is moving relative to the Sun's reference frame? And what about the fact that the Sun is moving relative to the reference frame of the Milky Way galaxy?If in fact the light pulse does miss the detector even though the emitter was pointed dead center at it, haven't you created a way to determine if you're in a moving reference frame from inside the reference frame? For instance - couldn't you use such a emitter-detector device to determine whether you were moving, or something was moving past you?And doesn't that, therefore, violate relativity? If you could build such an intrinsic motion detector, wouldn't that disprove Einstein's notions of relativity? How do you square that with the observation that our universe is relativistic?