Independence of speed of light and velocity of source

[jartsa]

Wrong. If, in the frame in which air is at rest, the membrane center moves diagonally, the induced compression wave will move diagonally. It's wave front will be approximately horizontal, but it direction of propagation will be diagonal. Just to be concrete (I actually tried this to see if it could be verified so simply, and it can), fill a tub with water and move your hand parallel to a side but in a diagonal direction versus a perpendicular direction and you will clearly see the difference in direction of wave propagation.

There is a difference, if anytime I change the direction of the motion of the hand, I also change the angle of attack of the hand, otherwise not so much.

Edit: I meant: There is a difference, if anytime I change the direction of the motion of the hand, I also change the angle of the hand, so that the angle of attack of the hand stays the same, otherwise not so much.

If we ask a diagonally moving hand, the tub has some backwards motion, which motion is carrying the waves with it.

 

[PAllen]

There is a difference, if anytime I change the direction of the motion of the hand, I also change the angle of attack of the hand, otherwise not so much.

If we ask a diagonally moving hand, the tub has some backwards motion, which motion is carrying the waves with it.

Wrong again. You can see the difference with NO change in angle of attack of the hand. (unless your universe behaves differently from mine). Look especially at where the wave front first makes contact with the opposite side.

 

[Ilja]

If I'm in a uniformly moving spaceship, and I throw a ball up to the ceiling, it will hit a spot that is directly above me. This is because the ball has inherited the velocity of the spaceship. I thought that light does not inherit the velocity of the source. Yet if a light pulse hits the spot directly above me, doesn't that mean that the horizontal component of the light's velocity inherited the horizontal component of the spaceship's velocity?

No, you can spot the light in any direction. It may hit, starting from one point on the ground, any point on the ceiling, not only the one directly above you.

In general, I would recommend you to read Bell's paper "How to teach special relativity". His point is that starting to learn relativity using the Lorentz ether one gets much better intuitions. This confusion seems to be a point. To get the correct intuitions, I think it is necessary to understand how relativity would work if the only way to send signals would be water waves. There would be a corresponding Lorentz symmetry with the speed of water waves instead of c. An important step to understand how this works is to understand that Einstein synchronization is a nice idea if you are really at rest, but trivially fails if you are not.

 

[spacediver]

thanks for the reference. I shall read that paper once I make my way through the Feynman chapter.

 

[jartsa]

Wrong again. You can see the difference with NO change in angle of attack of the hand. (unless your universe behaves differently from mine). Look especially at where the wave front first makes contact with the opposite side.

Yeah, but that does not convince me.

EM-wavefront segments emitted by a moving antenna gain distance to the antenna at different rates depending on the direction of the propagation of the segment. That's why the motion of the antenna affects the orientation of the wavefronts.

(velocity of a segment in the frame where the antenna is moving = relativistic addition of the velocity of the antenna and the velocity of the segment in the antenna frame)

All sound-wavefront segments emitted by a speaker in a moving spaceship gain distance to the speaker at the same rate. The motion of the speaker does not affect the orientation of the wavefronts.

(calculation is exactly the same as above, velocities just happen to be non-relativistic ones)