Special Relativity Part 3: Length Contraction

33 thoughts on “Special Relativity Part 3: Length Contraction”

1. Good lecture sir

2. Hi mga stem students ahahahahha

3. So if someone started from the moon and another person started from the earth, traveling in the same direction at the same speed, would their time dilations be different due to the fact that their inertial reference points were different thresholds for 0?

4. Thanks alot for such informative video.
   I just want to ask you, does this length contraction works only at the speed of light??
   The explanation today you provided has any relationship to that we see a aeroplane flying at a 25000ft??
   We can also observe the speed of aeroplane is slower compare to speed inside the aeroplane???
   Can you explain. Or it's just our biological effect of our eyes???

5. Is delta T zero the dilated time? I'm very confused? Very

6. May I embed your video in my blog ?

7. My mind does not have the capacity to process this!!!!

8. Would the astronaut's measuring tape also be dilated? How would they actually measure the ship as being 100M?

9. May I ask what is the value of c in the c^2? Every time I put (3.0×10^8)^2 in C^2 in the length contraction formula, it always ends up getting 1.

10. Unless I'm misunderstanding something, this seems to conflate length (difference in position between two parts of an object, which are at the same time wrt the observer, but might not be the same events for all observers), which does contract, and distance (change in position between two fixed events, which might not be at the same time wrt the observer even if they are for other observers), which dilates.

11. The formula for the first comprehension problem is actually incorrect. It should read Lo= L (square root 1-v^2/c^2) or gamma. Anyhow, if you are finding the length of the observer from the earth, that is the proper length which is Lo.

12. Thank you for this because when my teacher explained it, it went right above my head lmao. you're a life saver <3

13. I'm lost?

14. Wait so in the comprehension, why is L0 now shown as the length as seen from the astronaut’s view when you previously stated that in this scenario, L0 would be from the earth viewer’s perspective?

15. 한국인 있을까…

16. thank you! totally helpful, especially on 4:21

17. so, when you move at speed of light, your length should become zero? is that what happens with photon? But how your length can be less than plank length which is fundamental shortest length?

18. How about for the point view of photon it self. Length become zero because of length contraction. This is redicilious, we know photon need time to travel long distance, like from sun to earth they need 8 minute.???

19. 5:20 shouldn't the result be 100 / 0.527 instead of 100 * 0.527 according to how the value of a letter is found in math?

20. @Professor Dave Explains so does light have to travel a shorter distance due to length contraction because it its just apparent right?

21. I messed up….

22. Thank you so much Professor Dave. I have been struggling for the special relativity theory for a while, and thanks to your explanation; I'm good now.

23. so a person on Earth receives the spaceship as being 52 long while the person on the spaceship perceives it as being 100 m long but there must be some absolute length for the spaceship right so if the person on the spaceship where to get out a tape measure and to measure it would not come out to 52 meters long or when it come out to a hundred meters long?

24. Does length contraction and time dilation happens at the same time?

25. Well, I guess we guys are dodging the question about our size with almost the speed of light then, since our "spaceship" seems so much longer to us than to a female observer.

26. That checking comprehension problem can't be right…how is length measured by someone on Earth contracted?

27. explain why does this happen.
    what are you doing bro?
    only video editing?

28. the guy in the ship will measure contracted length right? then why did the length of ship appear increased in the solved example in the end?

29. Nice

30. For you time is what clock shows right.?.

31. I want to draw your kind attention that I do not understand the length contraction in checking comprehension part…can u solve my problem…u say that person on earth measures the correct lenght and it expresses by L not so how can the magnitude of L not is lesser than L i.e. the lenghth measures by an astronaut . here always L < L not…..pls explian me sir ???

32. Somehow I understood time dilation

    But I think this is a step too far, relatively speaking

33. How do I know when to use L0 vs L ?

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