If you see a supernova at the exact moment a dog barks, would you say the explosion of the star and the barking of the dog were simultaneous?
It's a moot issue. What's the clock for?
On the idea of time in physics-relativity
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SImultaneous events are those which an observer can assign the same clock-time to. The simultaneous space is three-dimensional, and in Minkowski 'geometry' one dimension is suppressed, so you have a hyperplane extending from the apex of the observer's nullcone.
Neddy Bate
Valued Senior Member
So you believe that macroscopic light does not behave logically. The light just "magically" reaches both observers at the same time, even though there is no way to draw a diagram of that without invoking invisible light rays.
Which specific part would you like to attempt to refute?
1. Two light beams emitted simultaneously in the train frame would reach the train observer simultaneously.
2. The train observer does not see the light to travel at any speed other than c.
3. Two light beams emitted simultaneously in the platform frame would reach the platform observer simultaneously.
4. The platform observer does not see the light to travel at any speed other than c.
How can you reconcile all of these in a single scenario? You cannot without allowing for relative simultaneity or a variable speed of light, the latter being overwhelmingly demonstrated to be false, especially by the MMX.
Could it be that your horrid misunderstanding stems mostly from your blinkered comprehension of that wiki image?
Figure 4. Expected differential phase shift between light traveling the longitudinal versus the transverse arms of the Michelson–Morley apparatus
This image you keep citing depicts what was "expected" prior to preforming the experiment, which did not demonstrate what is shown here (i.e. it was a null result).
In any case, the null result of the Michelson–Morley experiment helped the notion of the constancy of the speed of light gain widespread and rapid acceptance. -http://en.wikipedia.org/wiki/Michelson-Morley_Experiment#Special_Relativity
The constancy of the speed of light, verified by the MMX, is what makes all four points of mine accurate, and the only way to reconcile all of these is if two events observed to be simultaneous in one frame are not generally observed as such in another.
Exactly, as Syne has wonderfully shown the diagram above. If you tried to apply the logic in the TE to the MME, then the particles would not arrive at the same time, as shown above to the right. The experiment found that what actually happens is what is shown on the left. The left simulation has been shown to also be true when the experiment is considered to be in motion. So if I said the right diagram was on a train, then it wouldn't agree with experiment. But, I don't know what you mean by invisible diagrams and invisible light rays.
Time would actually have to be dilated and different in other frames so that the beams reach the detector at the same time. I don't believe in variable speed of light, and I have refuted it many times in the past. I don't know why you keep saying that I would think there is a variable speed of light.
I said, the observer on the train can assume that he is at rest. Then two beams of light are sent to him at the same time. They are the same distance away. They would then travel the same distance, at the same speed so then they would arrive at the same time. His direction of motion would not change the arrival times, because the observer on the train would measure the speed of light to be the same speed even though he was in relative motion to where the beams are sent.
It would be like saying that in the right simulation, the beams are sent from the back of the train and then one is reflected off the top of the train and the other is reflected from the front of the train. They both then meet at the bottom of the train. The right simulation is what happens in Einsteins thought experiment, the left simulation is what happens in actual experiments. The two do not agree with each other. The left simulation would be what should happen on the train! That has been what was found by actual experiments!
Layman, have you looked up relative simultaneity in a textbook yet?
Or looked at the extract I posted from Fundamentals of Physics?
Or even the Wikipedia link Neddy Bate posted?
Or are you so satisfied with your current understanding that you don't feel the need to check it against authoritative sources?
Or looked at the extract I posted from Fundamentals of Physics?
Or even the Wikipedia link Neddy Bate posted?
Or are you so satisfied with your current understanding that you don't feel the need to check it against authoritative sources?
How do you know they're sent at the same time?Layman said:
Because in the MME, they are sent from the same location from the same beam of light that is then just split with a half silvered mirror.
Have you looked up relative simultaneity in a textbook yet?
Or looked at the extract I posted from Fundamentals of Physics?
Or the Wikipedia link Neddy Bate posted?
How do you know the flashes in the train experiment are sent to the train observer at the same time?
If they were sent at different times, they would reach him at different times, right?
Or looked at the extract I posted from Fundamentals of Physics?
Or the Wikipedia link Neddy Bate posted?
That doesn't tell you anything about when the beams of light in the train experiment were sent.
How do you know the flashes in the train experiment are sent to the train observer at the same time?
If they were sent at different times, they would reach him at different times, right?
Have you looked at a laymans text that describes the MME, or other experiments that conclude that an object in motion will recieve beams of light at the same time?
In Einsteins thought experiment it assumes that the observer on the station measures the beams to be sent at the same time.
Now consider the train being in motion but assuming that it is at rest. The platform would send the two beams at the same time, and the velocity of light would not be affected by this relative motion. So then it would be like the platform of the station was in motion sending the beams at the train. If it sent the beams when the train was equidistant, then the observer on the train would receive them at the same time, as according to the MME.
Yes, I'm familiar with the Michelson Morley Experiment, having briefly studied it at University, and read about it in books both academic and popular since.
Have you looked up relative simultaneity in a textbook yet?
Or looked at the extract I posted from Fundamentals of Physics?
Or the Wikipedia link Neddy Bate posted?
Not quite. The assumption is that the lightning strikes at equal distances from the platform observer in such a way that the flashes reaches the platform observer at the same time.
The platform observer then concludes that the strikes occurred at the same time.
Are we considering the train at rest, or in motion?
If we are considering the train at rest, then we don't know if the flashes occurred at the same time or not. That conclusion was drawn by the platform observer.
Do you agree that if the flashes were not sent at the same time according to tht train observer, then they would not reach him at the same time?
I don't really care to talk to you anymore Pete. This is turning into the same discussion of your factorization of zero. I don't want to be brought down to your level.
From an observer at rest, it assumes that the lightning hit at the same time. I don't care to get twisted in your ideas that is something somehow different. Your concluding that the TE is correct, before the things in the TE even take place and applying it to the TE before that is even derived in the TE. I don't see any type of flow of real logic here really taking place. The TE says they arrive at different times, the MME says they reach at the same time. I will leave it at that. If you can't comprehend that, then you would be the one that needs to do the looking up of these things not me.
I was saying that the train assumes that he is at rest, and the platform is actually in motion sending the beams of light. I was trying to get you too look at it in a way that according to science the beams will arrive at the same time. If the train is at rest, and the platform is in motion sending the beams of light, then it will not change the measured speed. If they are sent when they are the same distance then they will reach him at the same time since the platform doesn't change the speed.
I don't care to answer your question because it is misleading, and it takes the discussion in a direction I do not want to go in. Of course they will not reach him at the same time if they are not sent at the same time, but that doesn't bring up anything that matters. In the TE the flashes are measured to occur at the same time relative to the observer at rest, this is a condition that then brings the consequence of events not being simultaneous in both frames. To say they don't occur at the same time in either frame is just nonsense.
From an observer at rest, it assumes that the lightning hit at the same time. I don't care to get twisted in your ideas that is something somehow different. Your concluding that the TE is correct, before the things in the TE even take place and applying it to the TE before that is even derived in the TE. I don't see any type of flow of real logic here really taking place. The TE says they arrive at different times, the MME says they reach at the same time. I will leave it at that. If you can't comprehend that, then you would be the one that needs to do the looking up of these things not me.
I was saying that the train assumes that he is at rest, and the platform is actually in motion sending the beams of light. I was trying to get you too look at it in a way that according to science the beams will arrive at the same time. If the train is at rest, and the platform is in motion sending the beams of light, then it will not change the measured speed. If they are sent when they are the same distance then they will reach him at the same time since the platform doesn't change the speed.
I don't care to answer your question because it is misleading, and it takes the discussion in a direction I do not want to go in. Of course they will not reach him at the same time if they are not sent at the same time, but that doesn't bring up anything that matters. In the TE the flashes are measured to occur at the same time relative to the observer at rest, this is a condition that then brings the consequence of events not being simultaneous in both frames. To say they don't occur at the same time in either frame is just nonsense.
I am reposting this in case you missed it Prof. Layman, I am wondering what you think.
Prof. Layman to better understand your position I have supplied a simple picture that shows a moving source (the dot, which is moving at a significant fraction of c) and an expanding light sphere (the circle). This is event is being viewed from an inertial reference frame that is stationary relative to the moving source. There are 2 cases shown. I have a very simple question - which one represent what would actually happen? If you have an questions about the set up feel free to ask.
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Prof. Layman to better understand your position I have supplied a simple picture that shows a moving source (the dot, which is moving at a significant fraction of c) and an expanding light sphere (the circle). This is event is being viewed from an inertial reference frame that is stationary relative to the moving source. There are 2 cases shown. I have a very simple question - which one represent what would actually happen? If you have an questions about the set up feel free to ask.
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It concludes from measurement made with the platform assumed at rest that the bolts struck at the same time.
Beause you'd rather accept a logical impossibility?
The logic is this:
Initial setup
- The train and platform are moving past each other
- The lightning bolts strike the train at equal distances from the train observer
- The lightning bolts strike the platform at equal distances from the platform observer
- The flashes reach the platform observer at the same time
Assumption:
- The speed of light is frame invariant
From the first setup item, we conclude that:
- The train observer has moved past the platform observer before the flashes reach the platform observer
Therefore
- One flash has already passed the train observer, the other flash has not yet reached the train observer
Therefore
- The flashes reach the train observer at different times
So, the train observer concludes that the lightning struck at different times,
and the platform observer concludes that the lightning struck at the same time.
This is well covered in standard textbooks. I suggest you read one. I posted an extract earlier in the thread, which I invite you to consider.
In my experience, when a question makes me uncomfortable it is a sign that I might be wrong, but don't want to admit it. It usually means I have to stop and think as objectively as I can about things that challenge my assumptions. It's not pleasant.
This is everything that matters. We now know that the MME doesn't say that flashes of light will always reach an observer at the same time - it depends on when and where they are initiated.
Consider it this way.
One lightning bolt strikes as the front of the train passes the back of the platform.
The other bolt strikes as the back of the train passes the back of the platform.
According to the platform observer, these happen at the same time, because the train is the same length as the platform.
But, the train is moving relative to the platform, so it is actually length contracted. The train's proper length is longer than the platform's proper length.
According to the train observer, the platform is length contracted, so the platform is shorter than the train.
This means that the back of the platform passes the front of the train before the front of the platform passes the back of the train.
This is the relativity of simultaneity.
With the platform at rest, the front of the train passes the back of the platform at the same time as the back of the train passes the front of the platform.
With the train at rest, the back of the platform passes the front of the train before the front of the platform passes the back of the train.
(You might recognize this as the Barn and Pole or Ladder or Train and Tunnel 'paradox')
That's what I thought when I first read about it.
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The first one, as observered from both frames. This is what is found in experiments. The secound would have to assume that the measurement of the speed of light is different in different directions. For examle, you couldn't find how fast your are actually traveling by what direction light beams arrive at different times that are the same distance away from you. All frames can assume they are at rest, and under this assumption they can all conclude that light will have the same behaivor from traveling at the same speed even if that frame is at a high velocity. Not that one frame will have beams of light going faster or slower relative to them in different directions!!!
Don't you ever get tired? Why do you have so much enthusiasm for bullshit?
Yes, then I will feel all smart logically deducing a reason why logic cannot apply to quantum mechanics. Then I would know what one of those reasons are, and have a better understanding of time dilation as a thing that actually occurs and is not just an illusion from tricks with mirrors. Only then can it then make any logical sense, the only way they can be seen to travel at the same speed at the same time is if they actually experience different degrees of the passage of time.
What I think is now may actually be a few brief moments before the time that you actually experience as now. I have already derived the proper time assuming that both observers will measure the beam of light to be at the same location simultaneously. The equation doesn't have to be different. It is just that the thought experiment wouldn't be a good tool to teach how light is actually measured to do in actual experiments. It wouldn't be a good way to develop theories. I think it was actually Einsteins ability to do math that has saved him here. I don't think this really affects the equation of the proper time or that it should be different. So then I am not saying all of physics is wrong, just this part of the mind experiment.
I suffer from delusions that I would actually end up having an intellegent conversation with someone about it. I just need to face the facts and realize that this will never happen because people like you will just say things like this even though they are wrong and reallyhave no idea about the actual facts about what they are talking about.
It is obvious that I could never show you how you are wrong about your own belief systems. So then we could never solve this problem or work on this problem together. We could only ever just throw insults at each other, and the only person I could ever be happy with working on such things would be myself. Only then could I be free of all connections that bring you to these false conclusions, and only be bothered by the actual logical conditions that present themselves that have a direct influence on what they pertain too.
What you seem to be missing here is that by choosing the first case you are going against the relativity and MME. The MME and relativity say that the speed of light is always measured as c in all frames. By choosing the first case you are saying that the stationary observer will see the light in front of the moving dot exceeding c (c + Vdot) and the light behind as moving less than c (c - Vdot).
Hopefully you can see that. Another way to look at this is to assume the time that elapsed was 1 second and look at the distance the light sphere expanded. The sphere started the expansion from the top of the drawing at the dot. After 1 second (the bottom of the drawing) the edge of the light sphere has moved more in the direction of travel than opposite the direction of travel - that violates relativity and the MM experiment.
This is the crux of your misunderstanding.
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This is where you are having problems. The behaviour will not be the same (if you like) but the speed will always be c. In the drawing I did the second choice shows the speed of light as a constant, the first choice (the one you chose) show exactly what you say cannot be, which is "one frame will have beams of light going faster or slower relative to them in different directions".
Let's try this imagine you are on a space ship that can travel at .99 c. At t=0 a light is flashed from your ship (at earth) as your ship instantly accelerates to .99c. Now for a stationary observer relative to your ship they would see that the light would reach alpha centari in 4.367 years. This must be correct because the speed of light is alway c in all frames and the distance is 4.367 ly, correct? The ship moving at .99 c would reach alpha centari in 4.41 years. This must also be correct because the distance divided by the velocity gives the time.
That would mean of course after 4.367 years of travel the light would only be .044 ly ahead of the space ship. This is case 2. The stationary observer will say that the light expanded out uniformly from it's source at earth at c. This is in complete agreement with relativity and the MM experiment. You don't actually think the the entire light sphere would move at .99 towards alpha centari!
Case 1 is also true but only for the space ship. That is because the speed of light is always measured as c from all inertal frames. So the ship will say the light sphere expanded outward from the source (the ship itself) at a uniform rate of c.