The discussion centers on the effects of Lorentz contraction on perceived distances at near-light speeds, particularly in the context of different frames of reference and the implications of acceleration. Participants explore theoretical scenarios involving moving objects and the measurement of distances in special relativity.
Participants do not reach a consensus on the effects of Lorentz contraction and acceleration on perceived distances. Multiple competing views remain, particularly regarding the implications of acceleration and the distinction between visual appearance and measured distances.
The discussion highlights the complexity of applying special relativity concepts, particularly in non-inertial frames, and the potential for misunderstanding the relationship between visual perception and physical measurements.
Length contraction is not about what you see visually, it's about what you measure using rigid rulers and clocks at rest relative to yourself (and only non-accelerating objects can remain rigid in relativity, so it's problematic to talk about what is 'observed' in this non-visual sense by a non-inertial observer). See this thread for more on the difference between measurements and visual appearances in SR. In fact, visually the length of a moving object appears exactly the same as the same object at rest--see this thread.duordi said:If I am the one who accelerated then the ship would appear to be closer just after the acceleration?
No, as I said, Lorentz contraction is not a matter of what is seen visually. Anyway, in this case neither the apparent visual difference nor the actual distance in my frame would change before and after the acceleration (assuming the acceleration was instantaneous).duordi said:Suppose a distant star was traveling 99% the speed of light away from me and it slowed down to 90% the speed of light. Eventually when the light reached me the lorentz contraction would decrease and the star would appear farther away.
No, that's definitely wrong.duordi said:As the distant star was slowing down it would appear to be accelerating away from me.
Am I right in this?
duordi said:So there is a lot of distortion and delay due to light travel.
Forget the camera, bad idea.
Suppose a distant star was traveling 99% the speed of light away from me and it slowed down to 90% the speed of light. Eventually when the light reached me the lorentz contraction would decrease and the star would appear farther away.
As the distant star was slowing down it would appear to be accelerating away from me.
Am I right in this?
If you accelerate, you're no longer an inertial observer. All the standard equations of SR, like the time dilation equation and length contraction equations, only apply in inertial frames. There is no standard definition of the "frame" of a non-inertial observer--distances and times in inertial frames are defined in terms of rigid rulers and clocks at rest in that frame, but rulers cannot remain rigid when they accelerate.duordi said:JesseM you lost me.
The two ships are 1 foot and 10 light years away from me and traveling 95% of light velosity away from me.
Now I accelerate to 95% light speed toward them.
Our velocities are identical, in my frame of reference.
No LorenTz contraction, the furthest ship must be farther away then it was before the distances between the ships were contracted before.
Are you claiming the universe will visually appear to contract, or are you claiming that in the coordinate system where you remain at rest throughout the acceleration, the rest of the universe will contract in that coordinate system? If the first I don't think that's correct, if the second, then see what I said above about the fact that there's no standard definition of the "frame" of a non-inertial observer, you could pick a variety of different coordinate systems where you're at rest and which disagree about what happens to the distance to other objects.granpa said:in the frame of the moving star light spreads outwards evenly in all directions. so when its contracted in the frame of a moving observer its light appears to mostly go outward perpendicular to its motion.
if you accelerate to 95% of c then the whole universe will appear to contract.
JesseM said:Are you claiming the universe will visually appear to contract, or are you claiming that in the coordinate system where you remain at rest throughout the acceleration, the rest of the universe will contract in that coordinate system? If the first I don't think that's correct, if the second, then see what I said above about the fact that there's no standard definition of the "frame" of a non-inertial observer, you could pick a variety of different coordinate systems where you're at rest and which disagree about what happens to the distance to other objects.