wespe
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ram1024 said:wondering if you guys have eyes...
no wonder we are having communication problems.
we can't even agree on something as simple as this.
ram1024 said:wondering if you guys have eyes...
so speed is distance over time
poke a pen on the center of emissions in picture 2. no relative motion is made towards the locations of the sources. indeed the locations of the sources seem to be traveling down the tracks. what's with that?
i'm not talking about the red dots. ignore the red dots completely.
poke your pen in the centers of the expanding spheres.
picture 1 = movement towards expanding sphere to the right
picture 2 = no movement towards expanding sphere to the right.
so what's going on?
ram1024 said:poke your pen in the centers of the expanding spheres.
picture 1 = movement towards expanding sphere to the right
it SHOULD not be moving. which means MOTION of the train should bring the train closer to it.
in the second image the train and the two sources/centerpoints move together.
i'm talking about moving relative to the tracks, just like the train is moving.
no no no hurkyl. the second picture is not the train stationary
what would be the point of comparing a moving train to a stationary one?
they both move in both pictures,
they're both supposed to get relative views of "what happens"
the problem is. in picture 1, the train makes definate relative movement towards the emitter to the right.
in picture 2 there is no movement towards it.
i can only conclude that the picture is somehow interpretting the data incorrectly OR, someone fudged the calculations intentionally.
Well here's the thing, and its a catch-22 for you: your definitions of words like "simultaneous," "reality," and "perception" aren't the definitions science uses. So even if you are correct that perception does not equal reality (you're not), you still have to stipulate to it for the purpose of examining what the theory says. Otherwise, you're arguing that the sky is orange and defining orange to be the color between green and indigo. You won't get very far in science with that approach.ram1024 said:see that's the thing, if simultaneity can be real at a single point, then simultaneity MUST be able to be real at a distance. not "according to an observer" but according to "reality".
to say it doesn't happen is like saying "no two things in the universe EVER happen at the same time"
whether or not they happen "at the same time to you" is merely a matter of perception and is NOT reality
what if you don't know your distance between the two distant clocks. In that case, if the signals reach you at different times, how can you figure out if the signals are simultaneous in another reference frame? (Hint: you can't.)
ram1024 said:no no no hurkyl. the second picture is not the train stationary, it's supposed to be the vantage point from the train IF the train was stationary.
what would be the point of comparing a moving train to a stationary one?
they both move in both pictures, that's the exercise, they're both supposed to get relative views of "what happens" to the same even viewed from two vantages.
the problem is. in picture 1, the train makes definate relative movement towards the emitter to the right.
in picture 2 there is no movement towards it.
i can only conclude that the picture is somehow interpretting the data incorrectly OR, someone fudged the calculations intentionally.
ram1024 said:so speed is distance over time
left light travels 1 full distance in 1/2 the time the right light.
left light is comparatively twice as fast.
what happened to relatively constant?
The two animations are different views of the same thing. In both animations, the sources are fixed (attached) to the track. Animation #2 takes the view of someone on the train (thats why the train doesn't move). The sources (red dots) certainly move. The centers of the light spheres never move in either animation: that's what "invariant speed of light" means--any observer will see the light moving in a perfect sphere from wherever and whenever it started according to him. The speed of the light has nothing to do with the speed of the source.ram1024 said:that's why source is in "parenthesis"
in picture two we're NOT making relative motion towards "the source (geometric center"
in picture one we are.
I'm not sure what calculation you are trying to do. If you are calculating the speed of the light: remember the speed of light is constant relative to you the observer. The animation shows this pretty well.let's assume that "the source" was an explosion and the physical source no longer exists.
how would you perform your calculations in picture 2?
remember the speed of light is constant relative to you the observer. The animation shows this pretty well.
Think of the source as emitting a single pulse of light and then shutting off. So, from an observer's view in describing how the light emanates from the source--all I care about is where the source was at the instant it flashed (according to me).ram1024 said:not if you take out the physical sources. basically you're saying that sources moving towards a stationary body and emitting photons simultaneously is exactly the same thing as sources stationary from a stationary body but emitting light non simultaneously.
Please do play "where's the photon"! It's very instructive. Just be aware that relativity (and reality) insist that photons always travel at speed c with respect to the observer.the difference is where reality would agree with it. I didn't want to resort to it, but play the "where's the photon" game with both pictures. unless you're going to tell me the location of the photon is "relative" as well it's pretty closed case.
ram1024 said:the difference is where reality would agree with it. I didn't want to resort to it, but play the "where's the photon" game with both pictures. unless you're going to tell me the location of the photon is "relative" as well it's pretty closed case.
wespe said:Ram, I understand what you mean: you want to run the two animations in parallel (you would have to move one of them manually to keep the trains aligned), then you want to see the egde of the spheres at the same positions all the time. But they won't be. If that was the case, there would be a common reality agreed in both frames. But, do you remember there was an animation I posted the link for. There were two frames skewed relative to each other in the time dimension. If we could run these animations skewed like that (instead of just parallel), you would see it makes sense. Maybe I could make such animations in flash.. But.. I'm not sure you would be convinced anyway.. In post#204, Hurkyl unbelievably bothered to make measurements on those animations for you, but you just ignored.. Nothing we say will convince you if you don't want to learn how this works..
is CLEARLY not listening to what we're saying. He's just glazing over the posts to find errors so he can get HIS point across. Then he wonders why all of our answers are different depending on the frame we are in!ot if you take out the physical sources. basically you're saying that sources moving towards a stationary body and emitting photons simultaneously is exactly the same thing as sources stationary from a stationary body but emitting light non simultaneously.
the difference is where reality would agree with it. I didn't want to resort to it, but play the "where's the photon" game with both pictures. unless you're going to tell me the location of the photon is "relative" as well it's pretty closed case.
Yes! Now put the two together: the events are simultaneous when viewed from one frame, but are not simultaneous when viewed from another.ram1024 said:but if you DO know the distance you CAN.
But only if they agreed on who'se frame would be considered the universal reference rame from which to do them. Remember, by any form of relativity, there isn't one. In fact, the top-down/outside-in reference frame we're using in our thought experiments does not exist in our hypothetical 2d universe. You could call it a virtual reference frame, one in which communication is instantaneous. But regardless, it still doesn't change the fact that you received the signals at different times....and simultaneity would be the same to everyone else who did their own calculations.
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Or just imagine a device to sychronize them:
at the half way point we have a device that emits a photon to each clock, when that photon arives at the clocks they tick. This synchronises the clocks in the staionary frame, but in a moving frame one photon will have further to travel than the other so they CANNOT tick at the same time in the moving frame. As our photon device sychronises the clocks perfectly in the rest frame this must hold true for all clocks that are synchronised in their rest frame whether we use this device or not.
observer1
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Using the laser pulse to synchronized their clocks (call them A and B) in their own frame is a perfectly good method, as jcsd explained. No problem there.ram1024 said:just in case you couldn't find the post here it is again
Case #6
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Same thing as case #5 except this time the two clocks use laser light and the distance between them to synchronize. They synchronize in such a way that the light from the center hits them both at what appears to them to be the same "time"
Rather than introduce acceleration, and endless arguments about how it would affect the answer, just introduce another observer (call him Joe) who happens to be moving by. Now your once "stationary" arrangement of laser plus clocks A and B is moving according to this new observer Joe. No one will claim that anything was done to "mess up" those clocks--Joe does nothing but pass by. No one will claim that clocks A and B were accelerated: pure canonical SR. (Note that acceleration can certainly be handled, but why complicate matters?)the train is them sped up FASTER in the direction it was traveling (let's say to the right) and another light is pulsed.
In my version, it easy to see that SR predicts that clocks A and B will do exactly what they always did. Why shouldn't they? No one did anything to mess with them.SR predicts they receive light non-simultaneous now (because of clocks getting messed up) even though nothing happened that changed clock synch relative to the other clock. (True / False)
SR further predicts that measurements made by moving observer Joe will show that those laser pulses arrive at A and B at different times according to Joe[/color].
I was trying to make things easy for you. But... if you insist on accelerating the train, just be sure to do it right. Accelerate each piece of the train uniformly (according to observers on the train) so that each piece is always moving together according to observers on the train. Do this right and the train will be accelerated and the clocks will not be affected (as far as folks on the train can tell). Once you get it moving to the speed you want (with respect to something else of course), fire off that laser again. SR predicts that the light will hit the clocks A and B at the same time according to observers on the train.ram1024 said:exactly why i didn't want to introduce more observers :|
thanks for not following the rules
drawing up case #7. i'll get through to you this time...![]()
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ram1024 said:Discuss.
Original Quote by JanusThe point is that there is no preferred frame of reference. You can not absolutely say whether it is the train or tracks that are "moving". Both observers have equal claim that it is they that are stationary and that it is the other that is moving. Thus each observer will measure events as if they are the in stationary frame. In this case, the train observer sees the flash expand outward at the speed of light as a sphere from the point of emission. But the initial emitters move away from that point.
Original Quote by wespe What's there to discuss? Yes, changing the perspective will not change measurements. Maybe you should tell what you think can be wrong.
ram1024 said:Case #7
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We are watching from a frame at rest. The emitter is moving. The time it takes for light to reach the observer is distance/c (since we are at "rest" compared to them) You could say we are in the observer's frame.ram1024 said:Case #7
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ram1024 said:Case #7
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ram1024 said:Case #7
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ram1024 said:Step 4 and 5. DOES matter where the OBSERVER moves. the light will NOT hit the observer at the same time.
I'm not sure what your point is, since in your last two steps you change to a different observer! Of course different frames measure different times.ram1024 said:Step 1, 2, and 3. doesn't matter where the emitters move, the light will hit the observer at the same time.
Step 4 and 5. DOES matter where the OBSERVER moves. the light will NOT hit the observer at the same time.
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Your steps 1, 2, and 3 seem to take a view from A's frame. But steps 4 and 5 take a view from a frame in which A is moving. Of course that frame will measure different times. It should be no surprize to you by now that time measurements are frame dependent.
Alkatran said:Alright Ram, you disagree with the pictures because of the non-simultanity. But remember that picture with space distorted through time? (It was UP (ahead) in the direction of movement, and DOWN (back) the other way) Guess what that means? The train experiences certain "spaces" before an unmoving observer (the ones ahead of the train), but it also experiences certain ones AFTER (the events behind the train). Do you get how that can both perceive them as different YET??![]()