So I'm kind of confused about length contractions, whenever I think about length contractions I think about the faster an object goes it will be able to impair more photons which would create an increasing length effect and I dont really get why the contraction actually happens. Is there a better way to think about length contractions xD?
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5$\begingroup$ Have you tried learning about SR from a proper SR textbook, especially preferably from a textbook covering the subject from Minkowski diagrams' perspective? $\endgroup$– naturallyInconsistentCommented Dec 15, 2023 at 2:16
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4$\begingroup$ What do you mean by "impair more photons"? $\endgroup$– PM 2RingCommented Dec 15, 2023 at 2:17
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2 Answers
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Length contraction is not an optical illusion, it's a real physical effect. The best way to think of this, or any other velocity dependent effect, is geometrically.
A "moving" object follows a path through spacetime that is rotated relative to a "stationary" object. Imagine drawing a graph with the t-axis vertical and x-axis horizontal. Then a position versus time graph of the ends of a stationary spaceship are two vertical lines. If the same spaceship is moving the lines remain parallel and the same distance apart but are rotated. The length of the moving spaceship relative to the stationary frame is found by drawing a horizontal line between the parallel (sloped) lines.
There is a complication in that spacetime geometry is Minkowskian rather than Euclidean, so this simple picture doesn't quite give the right answer. But it should give you some clue about what's happening: the length of the rocket is the distance between front and back of the rocket as measured at the same time, and different observers have different definitions of simultaneity.
answered Dec 15, 2023 at 2:28
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The length of a fast moving train as it passes through a station is the distance between the front and rear of the train at a given instant. If you get your timing wrong and, say, measure the position of the front of the train a second before you measure the position of the rear, the train will seem shorter, because the rear of the train will have moved forwards in the intervening second. That's how length contraction comes about. In two different reference frames moving relative to each other, there is no common 'now' along their direction of travel, so in a moving frame you are effectively measuring the positions of the two ends of an object at different times in its rest frame.
answered Dec 15, 2023 at 8:05