Simultaneity - Albert Einstein and the Theory of Relativity
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Video Description:
Imagine two observers, one seated in the center of a speeding train car, and another standing on the platform as the train races by. As the center of the car passes the observer on the platform, he sees two bolts of lightning strike the car - one on the front, and one on the rear. The flashes of light from each strike reach him at the same time, so he concludes that the bolts were simultaneous, since he knows that the light from both strikes traveled the same distance at the same speed, the speed of light. He also predicts that his friend on the train will notice the front strike before the rear strike, because from her perspective on the platform the train is moving to meet the flash from the front, and moving away from the flash from the rear.
But what does the passenger see? As her friend on the platform predicted, the passenger does notice the flash from the front before the flash from the rear. But her conclusion is very different. As Einstein showed, the speed of the flashes as measured in the reference frame of the train must also be the speed of light. So, because each light pulse travels the same distance from each end of the train to the passenger, and because both pulses must move at the same speed, he can only conclude one thing: if he sees the front strike first, it actually happened first.
Whose interpretation is correct - the observer on the platform, who claims that the strikes happened simultaneously, or the observer on the train, who claims that the front strike happened before the rear strike? Einstein tells us that both are correct, within their own frame of reference. This is a fundamental result of special relativity: From different reference frames, there can never be agreement on the simultaneity of events.
Tags for this video: Albert EinsteinTheory of Physics Relativity Science Simultaneity
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| Comments for this video on YouTube |
| First of all, ... ( 1 week ago by Neithax) |
| First of all, please and I mean please refer a speed to something. Speed with respect to what? The moon, Proxima Centauri? Second of all, no observers arise in REAL physical experiments as laser tests which proove the isotropy of light in the inertial frame earth. Third of all there is no proof for time dilation and there will never ever be. Don't come with the muon because it is clearly that the decay rates change. And length contraction has never been observed and never ever will be. |
| To which example ... ( 1 week ago by Neithax) |
| To which example are you referring? Give me physical examples, not thought experiments. |
| I am not a physics ... ( 1 week ago by heatmourning33) |
| I am not a physics expert so I don't know all the experiments that have been done or the basis behind them. I just know what I've read and thought I understood in textbooks. I dont know what you mean by there are no observers, you need something to detect what you are measuring in your experiment. A detector can create a signal in response to some physical property and an observer can view this signal. |
| Would this ... ( 1 week ago by heatmourning33) |
| Would this experiment do? In empty space two rockets consider themselves to be at rest Rocket A and Rocket B. Both rockets have identical clocks aboard which are synchronized. A accelerates to a constant speed 0.5c wrt B and proceeds like this for a certain period of time then stops and turns around before accelerating again to 0.5c until it meets B again where it stops. When the clocks are compared will they still be synchronized? It may be a thought experiment but it is definitely a doable one |
| As for experimental ... ( 1 week ago by heatmourning33) |
| As for experimental basis try searching "Experimental Basis of Special Relativity" on google. The first result cites lots of papers some old and some new on experiments derived to test SR. Do not attack me on my understanding of these papers because I have not really read any of them and probably wouldnt understand many if I did. Anyways these papers are published in real physics journals where they can be discussed and repeated by the rest of the scientific community. |
| I know. The only ... ( 1 week ago by Neithax) |
| I know. The only valid tests are the ones who prove the isotropy of light speed in our inertial frame earth. Which they then herald as proof for Einstein's very vague postulate. But outcomes or predictions of the special relativity are NONE. The physics community lost their objectivity a long time ago. The only thing that matters in the world of today is money. If you can obtain research grants by saying a lot of absurd stuff then people truly lost their senses. |
| First of all which ... ( 1 week ago by Neithax) |
| First of all which type of clock are you talking about? Well any clock in the rocket A will show discrepancies in their time measuring because A accelarates. Because of its acceleration an actual force is applied on the physical system which tries to produce stable periods of oscillations. Since that system is affected by force, it won't present time decently. Clocks never do anyway because they temselves are subject to the motion of particles which govern the tick rates. |
| In order to produce ... ( 1 week ago by Neithax) |
| In order to produce a light beam you need a source which generates emission points (x0) which send way beams of light (x) which will be recorded by a detector. Now what is the distance f between the detector (xd) and the emission points in any physical experiment: it stays the same. (xd - x0)2+(yd-y0)2+(zd-z0)2=(ct)2=f2. The time it will take to do its round trip is the same for any physical inertial system: (2*f)/c. That is true galilean invariance. No humans inserted. |
| Ok fair enough, ... ( 1 week ago by heatmourning33) |
| Ok fair enough, clocks arent perfect. But there are equations proposed to predict the differences in time for A and B. If this experiment was done at a high enough speed the time differences predicted by the equations would not be trivial. If these were within an accepted uncertainty of the meausred time. would this not be proof? It could be done over and over with different accelerations. |
| Also to say that ... ( 1 week ago by heatmourning33) |
| Also to say that the physics community is insane believing that SR have been supported by many experiments and that they are only driven by money is absurd. The way it works in the real world is if a paper published in a scientific journal is obviously wrong it is removed from the literature. If it was as simple as misintrepretation of emmision points this would have happened ages ago.I was posting on this video because I wanted to learn more about the subject.you seem to just spew conspiracies. |
| Neithax, Did you ... ( 1 week ago by fredw93) |
| Neithax, Did you notice that the video shows the lightening striking the moving train, and the lightening moves from left to right along with the moving train? And when the video shows the embankment observer's point of view, the video has to stop the train so the embankment observer can see both flashes at the same time. These oddities are not in the original thought experiment, but they must be in the video to try to get things to work out "right". |
| You're living in a ... ( 1 week ago by Neithax) |
| You're living in a fantasy world. In other branches of physics objectivity does exist though. But SRT is to theoretical physicists what christianity is to the Roman Vatican. It is sacred. SRT got everything to do with Maxwell equations in Gibbs notations. The notation Lorentz adopted. Lorentz, the guy who came up with a static ether. Special relativity was the "cure" for that electrodynamical model. It is too difficult to point that out in youtube. |
| Yea, yea, yea. Spot ... ( 1 week ago by Neithax) |
| Yea, yea, yea. Spot on. It is true it isnot the original train thought experiment. That is in another video. |
| The thing with ... ( 1 week ago by Neithax) |
| The thing with Einstein is that he doesnot consider that his origins are not the same in his two moving frames. Although he does give you hints in his original paper that he does though. Because in one of his equations he states that x' has to be infinitesimale small (so that the origins are really close together). So his SRT is only valid for very very small velocities. Einstein really fudged alot with his parameters. There are other nasty critters in his SRT |
| Neithax, then when ... ( 1 week ago by fredw93) |
| Neithax, then when we see the train observer's point of view in the video, the train is moving left to right, relative to the embankment, and so are the lightening flashes. This movement of the lightening flashes and the stopping of the train for the embankment observer are not in the original thought experiment. This video uses tricks to try to force the thought experiment to appear to be correct. The video is a hoax, and the original thought experiment contains errors. |
| Well you haven't ... ( 1 week ago by heatmourning33) |
| Well you haven't convinced me. Don't worry about it though. Christianity also doesn't have articles published in scientific journals so that analogy is a very bad one. Anyways the postulates that Einstein made make more sense to me now having read more about them so I guess commenting did help in some way. |
| That's nuts. Uh, ... ( 1 week ago by JusticeLeague9) |
| That's nuts. Uh, the good nuts. |
| That was interesting ( 1 week ago by rocketagent47) |
| That was interesting |
| that is true. but ... ( 5 days ago by Catrillis2) |
| that is true. but when it all boils down. the time frame is the same whether you are in the train or not. the example with the space ship and the flashes of light is false. they incorrectly represent mathematical properties in illustrating addition when multiplication should be administered. in other words. if there were a pair of twins, one went up on a space ship and the other stayed home. no matter what happened theyh would stay the same age. nothing can change that |
| that train was ... ( 5 days ago by DaBigEgg) |
| that train was moving :) |
| No the twin that ... ( 4 days ago by Hamburgler55) |
| No the twin that went on the spaceship would be slightly younger, assuming it was moving at high speeds for a long period of time. For more detail look up the "Twin Paradox". |
| that was a mindFUCK ... ( 3 days ago by Spektator100) |
| that was a mindFUCK! crazy interesting tho! |
| from whose point of ... ( 1 day ago by Catrillis2) |
| from whose point of view. from the twin in the spaceships point of view, the twin on earth is moving. so HE would be slightly younger. and vice versa. it cant happen. thats why its called a paradox |
| The train does not ... ( 5 hours ago by fredw93) |
| The train does not stop in the real thought experiment. See Chapter 9 of Einstein's 1916 book. And in his original thought experiment, the two lightening strikes hit the ground, not the front and rear of the train. And they don't move left to right with the train. This animation is not correct. |
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