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1) Is there any proof that indicates that the sizes of objects actually change size as the objects travel at speeds approaching c (the speed of light)?

2) If an object would travel at a speed close to c, then slow to a stop, would the object retain its original size?

Please explain length-contraction, I don't understand it!

2007-11-19 03:21:20 · 5 answers · asked by Michael n 2 in Science & Mathematics Physics

5 answers

"Proof" means logical deduction from simple axioms. Yes, it is proven that length contraction is a logical deduction from the axiom that the speed of light is constant in all reference frames. If c is invariant, then length contraction must be true.

"Verification" would mean doing an experiment to observe length contraction. Unfortunately, it is impossible to accelerate a macroscopic object to speeds required to observe this.

But time dilation is easy to observe, and is observed on a daily basis in particle accelerators and it too is an immediate conclusion from the constancy of c. So is the General Relativistic bending of light rays around the Sun, and a myriad of other observed phenomena. The speed of light itself is also easy to measure and is always c. Many attempts have been made to disprove Relativity, and none have ever succeeded. If Relativity is correct, then length-contraction must be true. Therefore, length-contraction is just as certain a phenomenon as time-dilation.

The object's length is frame-dependent. The object doesn't change length in its own reference frame at all, so if you go into its reference frame (by making it appear at rest somehow, by slowing it down or speeding yourself up) it will appear its rest-length.

2007-11-19 04:05:26 · answer #1 · answered by ZikZak 6 · 1 0

I'm not a physicist, and haven't read up on this in a while....my instincts say that length contraction is sort of a corollary to time dilation (the whole theory, after all, says that time and space aren't distinct); because time is passing differently for you than stationary observers, distance and length also change concomitantly. That is, an object will appear, TO THE MOVING OBSERVER, to have changed size, but to a stationary observer there will be no change. So when the moving observer slows down and stops, the object will retain its "original" size, as the moving observer will now be an inertial observer with the stationary observer. The perception of changes in size is only relative, just as changes in perception of time. This all may be talking out my ***, however.

2007-11-19 03:35:24 · answer #2 · answered by fleepflawp 4 · 1 0

I do not know about proof that the size of things change but there are measurements made of the effect on time. Experiments have been done comparing the timing of two different atomic clocks, one which is moving rapidly with respect to the other. I believe these measurements agree well with the theoretical predictions.

If I understand the theory, an object would return to it's original dimensions.

One aspect of this that is difficult for me is the issue of the speed of light being universal, i.e., independant of reference frame. If your reference frame is the earth, light is traveling away from the earth at the speed of light. One could say that, from the reference frame of that photon of light, the earth is travelling away from it at the speed of light.

There is a good reason why the study of theoretical physics is complex. good luck

2007-11-19 03:33:49 · answer #3 · answered by Gary H 7 · 0 0

first of all, the "s" in your image should be a "t" for traveler and then use s for the stationary guy at the station. ok... if the train is traveling perpendicular, from right to left, then yes the observer will see the same thing as the traveler..... for every degree AWAY from the observer the train and tracks "rotate" the "degree" of contraction expands, exponentially, in an asymptotic curve towards infinity.. When the train is traveling DIRECTLY way from the observer ALL perceived motion stops. So in a sense you are both right... there is ONE condition where the observer and the traveler share the experience of simultaneous light beams returning... perpendicular travel, at 90 degrees to the field of vision... But under MOST of the orientations as the train travels away, the apparent length contracts and the distant observer sees a distorted image of what REALLY occurs. That is the heart of Einsteins theory. The DISTANT OBSERVER cannot accurately say what occurred without using some VERY ugly math.

2016-05-24 04:48:39 · answer #4 · answered by ? 3 · 0 0

There can be no observable proof of this because the original length returns when the object comes back to ordinary speed. It is a difficult concept to grasp. We accept it because Einstein says it is so,

2007-11-19 04:22:01 · answer #5 · answered by johnandeileen2000 7 · 0 1

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