Special Relativity: Crash Course Physics #42
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Date: 2022-04-04
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Comments and reviews: 10
Gin
I have something bugging on my mind for so long regarding the theory of relativity.
Every single video about the theory of relativity explains it using the same analogy. Alex is inside a train, moving really fast (let's say half the speed of light, and Bill is watching from a station.
Now, both of them shoot a laser beam to a mirror one meter in front of them, horizontally. Because Alex is moving, Bill would see Alex's beam moving diagonally instead.
Therefore, Alex's beam must travel a longer distance to reach the same meter, but because the speed of light must always be constant, time slows down for Alex instead.
My question. Idk if I visualize it wrong.
So, if Alex's time has slowed down, and Alex is punching his face inside the train, Bill would see Alex punching his face really slowly, even tho Alex is travelling faster in space?
Now, let's say Bill is als punching himself in the face, and Alex is watching from the train, he would see Bill punching himself really quickly? Why is Bill moving quicker than Alex even tho Alex is the one moving at half the speed of light?
Isn't that different from what we see in movie scenes with speedsters? Like in X-Men Days of Future Past, Quicksilver is the one moving really fast, and the other people are the ones stopping in time.
Time dilation explains the opposite. If Quicksilver is moving really fast and he obeys the special relativity, he would see the other people around him moving faster instead.
Or, am I wrong at understanding this? Please tell me why. I'm soooo confused.
No one has answered this question for me, and now my brain is fried.
reply
I have something bugging on my mind for so long regarding the theory of relativity.
Every single video about the theory of relativity explains it using the same analogy. Alex is inside a train, moving really fast (let's say half the speed of light, and Bill is watching from a station.
Now, both of them shoot a laser beam to a mirror one meter in front of them, horizontally. Because Alex is moving, Bill would see Alex's beam moving diagonally instead.
Therefore, Alex's beam must travel a longer distance to reach the same meter, but because the speed of light must always be constant, time slows down for Alex instead.
My question. Idk if I visualize it wrong.
So, if Alex's time has slowed down, and Alex is punching his face inside the train, Bill would see Alex punching his face really slowly, even tho Alex is travelling faster in space?
Now, let's say Bill is als punching himself in the face, and Alex is watching from the train, he would see Bill punching himself really quickly? Why is Bill moving quicker than Alex even tho Alex is the one moving at half the speed of light?
Isn't that different from what we see in movie scenes with speedsters? Like in X-Men Days of Future Past, Quicksilver is the one moving really fast, and the other people are the ones stopping in time.
Time dilation explains the opposite. If Quicksilver is moving really fast and he obeys the special relativity, he would see the other people around him moving faster instead.
Or, am I wrong at understanding this? Please tell me why. I'm soooo confused.
No one has answered this question for me, and now my brain is fried.
reply
Oliver
Hi. I believe that one of your examples is incorrect. At 6: 36 you say, -We already know that time moves faster for you than for Bob. Whilst 666 nS has passed for Bob, only 577 nS passed for you. - These two sentences are contradictory. If -time moves faster for you than Bob-, then the amount of time elapsed for you (person on the platform) must be greater than for Bob. The time elapsed for the observer on the platform should be 769ns, not 577ns. This is also consistent with the twin-s paradox and the idea that -a moving clock runs slow-. From the twins paradox, we expect the observer on the fast moving object (in this case, the train) to age less than the stationary observer (person on platform. Thus, time elapsed for Bob on the train must be less than for the person on the platform. From, -a moving clock runs slow-, we also anticipate that Bob-s recorded time will be less than that recorded from the platform. To summarise, if Bob records 666 nS from the train, you record 769 on the platform. Happy to be corrected, but I believe that this is correct.
reply
Hi. I believe that one of your examples is incorrect. At 6: 36 you say, -We already know that time moves faster for you than for Bob. Whilst 666 nS has passed for Bob, only 577 nS passed for you. - These two sentences are contradictory. If -time moves faster for you than Bob-, then the amount of time elapsed for you (person on the platform) must be greater than for Bob. The time elapsed for the observer on the platform should be 769ns, not 577ns. This is also consistent with the twin-s paradox and the idea that -a moving clock runs slow-. From the twins paradox, we expect the observer on the fast moving object (in this case, the train) to age less than the stationary observer (person on platform. Thus, time elapsed for Bob on the train must be less than for the person on the platform. From, -a moving clock runs slow-, we also anticipate that Bob-s recorded time will be less than that recorded from the platform. To summarise, if Bob records 666 nS from the train, you record 769 on the platform. Happy to be corrected, but I believe that this is correct.
reply
education
If rocket is traveling at 95%seed of light and going away from earth. light will take more time to travel from rocket to earth. let's say after one hour of traveling observer will see location of photon one hour late from its actual location just as when we observe star in sky we receive light that traveled many years and reached earth. so if we find a way to teleport instantly star will not be there. It was there years ago when light was emitted.
Now considering this observer on earth will see time on ship getting slower as it goes away n faster if it comes towards earth. plz correct me if I'm wrong. we know light travels in straight line same goes for photon so when ship moves ahead and our clock moves photon after first reflection should collide with side wall to maintain its straight line as at rest. I have seen many videos on this topic but there is no video that explains why there is change in direction of traveling photon it should be going straight up
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If rocket is traveling at 95%seed of light and going away from earth. light will take more time to travel from rocket to earth. let's say after one hour of traveling observer will see location of photon one hour late from its actual location just as when we observe star in sky we receive light that traveled many years and reached earth. so if we find a way to teleport instantly star will not be there. It was there years ago when light was emitted.
Now considering this observer on earth will see time on ship getting slower as it goes away n faster if it comes towards earth. plz correct me if I'm wrong. we know light travels in straight line same goes for photon so when ship moves ahead and our clock moves photon after first reflection should collide with side wall to maintain its straight line as at rest. I have seen many videos on this topic but there is no video that explains why there is change in direction of traveling photon it should be going straight up
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LoveAndNuance
I don't understand the bit about the two flashes of lightning occuring at a different time when you're on a moving train. I understand that you won't see them at the same time, because it takes a while for the light to reach you, but you can calculate how long it would take the light to reach you to see how long ago the lightning strikes actually did occur. Like when I observe a star, based on how far away the star is, I know I'm really observing the star from a million years ago.
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I don't understand the bit about the two flashes of lightning occuring at a different time when you're on a moving train. I understand that you won't see them at the same time, because it takes a while for the light to reach you, but you can calculate how long it would take the light to reach you to see how long ago the lightning strikes actually did occur. Like when I observe a star, based on how far away the star is, I know I'm really observing the star from a million years ago.
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Eliir
5: 10 this part can be a bit confusing. If the observer at the train station see's the lightning hit both ends of the train at the same time, then the observer on the train will see lightning strike the front first, then the back; this is true.
IF however, the observer on the TRAIN see's lightning strike on both sides of the train, then the observer at the train station will see lightning hit the BACK first, then the front.
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5: 10 this part can be a bit confusing. If the observer at the train station see's the lightning hit both ends of the train at the same time, then the observer on the train will see lightning strike the front first, then the back; this is true.
IF however, the observer on the TRAIN see's lightning strike on both sides of the train, then the observer at the train station will see lightning hit the BACK first, then the front.
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David
Absolute simultaneity is a meaningful concept if you adopt a Lorentzian interoperation of relativity, which supposes a privileged ether frame. The time dilation and length contraction are merely reflections of distortions of the instrumentation, not in the actual objects themselves.
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Absolute simultaneity is a meaningful concept if you adopt a Lorentzian interoperation of relativity, which supposes a privileged ether frame. The time dilation and length contraction are merely reflections of distortions of the instrumentation, not in the actual objects themselves.
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David
The finite math of a given perceived observation of reality lies within the ratio of 1: 2, that ratio being the finite math decimal subset between -. 1 through. 9-, the finite space holding infinite mass is merely the subsequent infinite decimal subsets of -. 1111, .12222, .-
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The finite math of a given perceived observation of reality lies within the ratio of 1: 2, that ratio being the finite math decimal subset between -. 1 through. 9-, the finite space holding infinite mass is merely the subsequent infinite decimal subsets of -. 1111, .12222, .-
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Murray
-Please HELP-
Surprisingly, I can understand the content of this video. (Given light has a speed limit) where I struggle is knowing with 100% absolute certainty that light has a speed limit. How do we know that our tools to measure the speed of light aren-t flawed?
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-Please HELP-
Surprisingly, I can understand the content of this video. (Given light has a speed limit) where I struggle is knowing with 100% absolute certainty that light has a speed limit. How do we know that our tools to measure the speed of light aren-t flawed?
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MeltingWax
At 4: 37, shouldn't the 'T zero' be the time in the moving reference frame (dilated time) and 'T' be time for stationary reference frame to make more sense. Correct me if I am wrong. Studying for A-level physics and was just wondering.
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At 4: 37, shouldn't the 'T zero' be the time in the moving reference frame (dilated time) and 'T' be time for stationary reference frame to make more sense. Correct me if I am wrong. Studying for A-level physics and was just wondering.
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Ana
Min 4: 35, is it right? gamma>1 and this means t>t0. and according to her labels. the observer who's travelling measures the greates time and that's wrong. maybe there is a mistake. t0 usually means the proper time.
Thanks.
reply
Min 4: 35, is it right? gamma>1 and this means t>t0. and according to her labels. the observer who's travelling measures the greates time and that's wrong. maybe there is a mistake. t0 usually means the proper time.
Thanks.
reply
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