kkris1

This original Einstein's "thought experiment", which is somewhat different to your interpretation: "When we say that the lightning strokes A and B are simultaneous with respect to the embankment, we mean: the rays of light emitted at the places A and B, where the lightning occurs, meet each other at the mid-point M of the length A —> B of the embankment. But the events A and B also correspond to positions A and B on the train. Let M' be the mid-point of the distance A —> B on the travelling train. Just when the flashes 1 of lightning occur, this point M' naturally coincides with the point M, but it moves towards the right in the diagram with the velocity v of the train. If an observer sitting in the position M’ in the train did not possess this velocity, then he would remain permanently at M, and the light rays emitted by the flashes of lightning A and B would reach him simultaneously, i.e. they would meet just where he is situated. Now in reality (considered with reference to the railway embankment) he is hastening towards the beam of light coming from B, whilst he is riding on ahead of the beam of light coming from A. Hence the observer will see the beam of light emitted from B earlier than he will see that emitted from A. Observers who take the railway train as their reference-body must therefore come to the conclusion that the lightning flash B took place earlier than the lightning flash A. " Einstein maintained that because middle point M inside the train was moving towards the front flash as well as receding from rear flash, both signal will not arrive in the midpoint at the same time. BUT BOTH FLASHES HAVE OCCURRED AT THE SAME TIME IN RESPECT TO THE TRAIN!!! Just the signals from both ends will not meet in the midpoint M.This obvious contradiction to his own theory. Einstein's explanation of time dilation is also seriously flawed. In his explanation the light was reflected from the mirror on the ceiling inside boxcar travelling in horizontal direction in regard to stationary observer. It was concluded that even if the light was emitted perpendicular to the mirror, for external observer it would appear to be travelling on angle. Because speed of light is constant, therefore time would have to be longer. But what if there are two light rays , one vertical and one directed towards the back of the boxcar on such angle that external observer would perceive it as vertical, emitted simultaneously.For external observer the vertical ray (in his frame of reference) would travel longer, than slanted ray. Another illogical paradox:the twin paradox. Einstein's reasoning was that the twin brother which stayed at home would age more than the travelling one.Somebody pointed out that because there is no absolute reference frame, we could say that the brother which stayed at home was actually travelling in reference to the astronaut twin. Some scientists argue however that the travelling brother would have to accelerate, deccelerate and turn around,therefore his situation would be entirely different. Now let's imagine there are triplets instead of twins and two of them started their journey towards the star. After reaching cruising speed one of them decided to return to the Earth.He would undergo the same acceleration, deceleration and change in direction as the other one which has completed his journey. Now how would you explain him ageing more than the one who went to the star? There are also some more points, like theory of light which can be explain differently, (the light could be explained using wave theory; I can prove that exponentially decaying wave has its total energy proportional to its frequency).

The second animation is not reflecting the truth of the Einstein's "thought experiment" He stated clearly: "two lightning bolts strike simultaneusly both ends of the boxcar leaving the marks on the car and on the ground". If the strikes occurred at the same time, detectors at both ends of the boxcar would record the same time of the strikes. The animation is quite nice but totaly untrue, it does not reflect the "thought experiment" devised by Einstein. He said that the boxcar will be "hastening"towards the signal from the front, while "receding"from the signal from the back. That was the contradiction to his own postulate that the speed of light is constant, regardless of the frame of reference On your first animation the flash reaches the front and the back of the boxcar at the same moment. The detectors at both ends would be activated exactly at the same time. If they were emitting the light, say one red and one blue, both red and blue rays should reach the middle of the boxcar simultaneusly. The second animation shows entirely different scenario, it is just not from the same experiment.

If you look closely at your animation, you will see that the flashes at both ends of the boxcar are simultaneus. So two observers will record the same time for the flashes close to them. (If say there is the screen in the middle blocking the flash from the far end, and the two observers have to compare their recorded times) Also according to your animation, there will be an observer somwhere past the middle point, to whom both signals will arrive at the same time. He is still in the same reference frame, but will strongly disagree with the guy in the middle

Now consider the situation: observers at both ends of the boxcar can measure the time of the strike at their respective ends If the transition time can be neglected, they can compare the recorded time and state indeed that the event were simultanous. If they measure the time the signal has arrived from opposite end of the car, their statements would be, according to Einstein's reasoning, totaly different. For the observer at the end of the boxcar, the boxcar will be "hastening" towards the light from the front flash. The observer at the front will be receding from the signal from the back of the boxcar. So the observer from the back of the car will record the interval between two flashes being shorter than observer from the front of the boxcar. But they are both in the same inertial frame and should get the same results.

Hi bombus, I do not think you can prove any theory once and for good. You can have 100's of "proofs" to support a theory, but if you find one experiment which disagree with it, your theory is wrong. As for Einstein, I think he was wrong on number of occassions. Look at his reasoning regarding time dilation or simultaneity: I would like to comment on Einstein’s “thought experiment” regarding time dilation. In his explanation the light was reflected from the mirror on the ceiling inside boxcar travelling in horizontal direction in regard to stationary observer. It was concluded that even if the light was emitted perpendicular to the mirror, for external observer it would appear to be travelling on angle. Because speed of light is constant, therefore time would have to be longer. But what if there are two light rays , one red and one blue , emitted simultaneously as shown on the diagram below? (see attachement, I couldn't copy the diagrams accross) For stationary observer the light would appear to travel shorter distance (blue ray) in longer time! Also so called “simultaneity thought experiment” appears to be naïve and entirely wrong. Let’s recall the Einstein’s scenario: Quote“ UP to now our considerations have been referred to a particular body of reference, which we have styled a “railway embankment.” We suppose a very long train travelling along the rails with the constant velocity v and in the direction indicated in Fig. 1. People travelling in this train will with advantage use the train as a rigid reference-body (co-ordinate system); they regard all events in reference to the train. Then every event which takes place along the line also takes place at a particular point of the train. Also the definition of simultaneity can be given relative to the train in exactly the same way as with respect to the embankment. As a natural consequence, however, the following question arises: 1 Are two events (e.g. the two strokes of lightning A and B) which are simultaneous with reference to the railway embankment also simultaneous relatively to the train? We shall show directly that the answer must be in the negative. FIG. 1. 2 When we say that the lightning strokes A and B are simultaneous with respect to the embankment, we mean: the rays of light emitted at the places A and B, where the lightning occurs, meet each other at the mid-point M of the length A —> B of the embankment. But the events A and B also correspond to positions A and B on the train. Let M' be the mid-point of the distance A —> B on the travelling train. Just when the flashes 1 of lightning occur, this point M' naturally coincides with the point M, but it moves towards the right in the diagram with the velocity v of the train. If an observer sitting in the position M’ in the train did not possess this velocity, then he would remain permanently at M, and the light rays emitted by the flashes of lightning A and B would reach him simultaneously, i.e. they would meet just where he is situated. Now in reality (considered with reference to the railway embankment) he is hastening towards the beam of light coming from B, whilst he is riding on ahead of the beam of light coming from A. Hence the observer will see the beam of light emitted from B earlier than he will see that emitted from A. Observers who take the railway train as their reference-body must therefore come to the conclusion that the lightning flash B took place earlier than the lightning flash A. We thus arrive at the important result: 3 Events which are simultaneous with reference to the embankment are not simultaneous with respect to the train, and vice versa (relativity of simultaneity). Every reference-body (co-ordinate system) has its own particular time; unless we are told the reference-body to which the statement of time refers, there is no meaning in a statement of the time of an event. 4 “ end of quote Now let us reiterate the logic of the experiment: two lightning bolts strike simultaneously both ends of a boxcar leaving the marks on the ground and on the boxcar. For an external observer O both strikes appear to be simultaneous however for the observer O’ who is right in the middle the flash of light from the front of the car arrives faster than from the back, because the boxcar “is hastening” towards the flash. But if the event is not simultaneous for the person in the middle, it should also appear the same for everybody else inside the car since they all are in the same inertial frame and they can synchronise their watches to confirm the exact moment the lightning occurred. If we happened to have extra 2 observers, one at the back and one at the front, they could indeed record exact time of event and confirm that the two strokes happened at exactly the same moment. But there is still more to it. If the one at the end of the boxcar measured the time after which the light from the front lightning arrived to him (and knowing the length of the boxcar), he would think that either his time flows slower or the light travels faster than c. Similarly the observer at the front of the car would think (after measuring the time the light took to travel from the end to the front of the car) that the speed of light is slower than c or his time runs faster. However both front and end observers are in the same inertial frame, so if there is a time expansion or contraction, it should be the same for both of them. Time dilation.doc

Yes, I think you are right.The problem is you stopped too early. If you calculate this exponential decay you'll find out that for small attenuation of energy you can get the same equation F=GM1M2/d^2 . Check my post (attachement) regarding it. As for classic gravity theory imagine infinite row of uniform spheres of radius r/2 and mass m touching one another. You'll find out the force acting upon first sphere from infinite number of such spheres (and infinite mass) is quite finite and equals: F=(Gm^2/r^2)*pi^2/6 from which most contribution comes from second sphere. Happy calculations. Kris

Hi Tannin, Thanks for your great contribution. But I still need some clarification: In first diagram the vertical ray will hit the ceiling of the spacecraft earlier then slanted one. But from stationary observer point of view vertical ray becomes slanted forward and slanted backwards becomes vertical.Still the events order should be the same as inside spaceship. Therefore from stationary observer's point of view the slanted ray will hit the ceiling first, thus covering longer distance in shorter time. Could you explain why order of these events (rays hitting the ceiling) in your second diagram is reversed in your description?

Well, if you know you are correct that's great, you do not need to learn anything . I'm not so sure if I'm correct as well. But I still would strongly suggest read some more info. E.g on the website: http://www.phys.unsw.edu.au/einsteinlight/jw/module4_time_dilation.htm

I would suggest read about this famous Einstein's "thought' experiment and you will know what we are talking about. I'm not trying to be rude, but i can see you completely misunderstood it

I think you do not understand it. Time dilation doesn't apply to two events observed in one inertial frame, it supposedly applies to one event viewed from two different inertial frames

The length contraction is irrelevant. If time dilation is explained as straight (vertical) ray in one inertial frame becomes slanted in second "stationary" inertial frame, so slanting backwards ray in first inertial frame will become straight (vertical) in second frame. And it is not a matter of "silly" mistakes which you can choose to ignore because the result is right. Before Copernicus discovered the Earth was not centre of universe people could calculate and predict events like solar eclipses with great accuracy, even if their theories were wrong. Physics is not a religion where you have to believe established truths with no rights to question them.

But the change in direction of light is not neccesary for our discussion; so for stationary observer it would appear the slanted light would reach the ceiling when vertically travelling ray would cover,let's say 0.7 of the distance to the ceiling.Since velocity is in horizontal direction only, we can exclude any height contraction. The distance travelled vertically by both rays in relation to the spaceship should be the same in both inertial frames.

Could anyone explain this? See attachement Time dilation.doc

See attachement . It should clarify the issue Fermat_Theorem1.doc