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News Breakthrough Prize

  1. Nov 10, 2015 #1

    OmCheeto

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    This is kind of neat.

    I watched the video by the student, and although it was very good, I still don't understand relativity. :redface:
    There are a bunch of https://www.breakthroughjuniorchallenge.org/finalists#winner [Broken] by other students. I got 1/3 of the way through one of the other 4 finalist's video, and decided it was also over my head. Good god these kids are smart! :oldsmile:

    I thought that was very nice that the winning student got $250,000 for university, and his high school received a $100,000 lab, and one of his instructors received $50,000.

    And the $3,000,000 won by some of the pros was probably appreciated, also.

    "belief"?
    pfft!!!
    google: Brian May
    :oldbiggrin:
     
    Last edited by a moderator: May 7, 2017
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  3. Nov 10, 2015 #2

    Borg

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    Thanks OM. I'll have to check out the student's video and see if I can learn anything new. :oldsmile:
     
  4. Nov 10, 2015 #3

    bcrowell

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    https://www.washingtonpost.com/news...eins-theory-of-relativity/?tid=pm_local_pop_b

    I thought this was pretty well done, for a pop-sci presentation. He has an interesting argument for time dilation based on Einstein's 1905 postulates of SR. As presented it's pretty hand-wavy, but it's an interesting idea, is different from anything I've seen before, and could conceivably be made more rigorous.

    He was awarded a pile of prize money for himself, his school, and his teacher.
     
  5. Nov 11, 2015 #4

    OmCheeto

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    I also thought it was pretty well done, for someone in high school. I was still perfecting "picking my nose" at that age.
    Have you watched any of the 15 other videos in https://www.breakthroughjuniorchallenge.org/finalists#winner [Broken]?
     
    Last edited by a moderator: May 7, 2017
  6. Nov 11, 2015 #5

    Borg

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    I did actually learn something. At the 5 minute mark - "The speed of light is constant as long as you are measuring it from a reference frame moving at a constant velocity". However, I'm not sure how it changes if your reference frame is accelerating. This is probably why I can't explain the twin paradox very well.
     
  7. Nov 11, 2015 #6
    250K for a non-mathematical presentation of introductory special relativity?! Wth!!
     
  8. Nov 11, 2015 #7

    mfb

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    It becomes unclear how to measure "speed" while accelerating.
    You don't need accelerated reference frames for the twin paradox. You just have to accept that spacecrafts can switch reference frames.
     
  9. Nov 11, 2015 #8

    Borg

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    Interesting. I would have thought that something like that would be understood and was just beyond my mathematical abilities. I will have to think on that one.
    I will keep that in mind the next time I review an explaination of the twin paradox.
     
  10. Nov 11, 2015 #9

    bcrowell

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    It's possible to explain the twin paradox without reference to any frame of reference whatsoever.

    If you do want to use frames of reference, then there is nothing compelling you to switch frames. A frame of reference is not a physical object like a spaceship. The traveling twin's motion is noninertial. Similarly, if I throw a ball, the ball's motion is noninertial, but that doesn't compel me to adopt the noninertial frame tied to the ball.
     
  11. Nov 11, 2015 #10

    OmCheeto

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    Way beyond my mathematical abilities.
    There are about 70,000 threads devoted to the subject at PF alone.
    I skimmed through 6, and couldn't understand a single one of them.

    From an uber-layman standpoint, I doodle pictures in my head, as to what is going on.
    I really have no idea if they are correct or not.

    In the following image, Einstein and Euclid, sitting where you and I are, get messages from George and Fred, positioned at points A and B, regarding the time stamp that it took photons to get from points A and B.
    Euclid sees the blue line between A and B, and determines that the time stamps indicate light didn't move fast enough.
    Einstein, with all his "woo woo" mathy stuff, sees that light still traveled at "c".



    relativity.light.star.jpg
     
  12. Nov 11, 2015 #11
    Well light is just moving along a geodesic, and locally, the 2nd postulate of SR holds. It's just that Euclid would think a "straight line" is a geodesic, but Einstein would think otherwise.

    That's the shortest way I could put it.
     
  13. Nov 11, 2015 #12

    OmCheeto

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    This is probably why the kid won. You've used terms grandmama would have not known, or would have misinterpreted.

    Geodesic? That's that Fullerian dome thing. I didn't know that Buckminster and Albert were even friends.
    Locally? Like my next door neighbor?
    2nd Postulate? Was that Peter or Paul?

    Sometimes, the shortest way, is not the best way.

    ps. Please don't try and explain the terms to me. I know how to google. I was just trying to make a point, that not all people know what the "Sagnac effect", nor "Born rigid spaceships", are. And the terms, are endless...... I hope next year's kid gets a million dollar scholarship.
     
  14. Nov 12, 2015 #13

    mfb

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    You cannot even introduce the paradox without using a reference frame in some way.
    You do not have to switch reference frames, but then some questions (mainly related to the view of the travelling twin) stay without an answer.
     
  15. Nov 12, 2015 #14

    bcrowell

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    "The" paradox actually has many formulations. Here is an example of a formulation and a resolution that never deal with a frame of reference.

    Formulation: Twin A stays on earth while twin B goes to another solar system and returns. Since motion is relative, either twin can be said to have remained at rest the whole time. The situation is totally symmetrical. How, then, can they have unequal ages when reunited?

    Resolution: The situation is not symmetrical. Relativity distinguishes between inertial and noninertial motion. Twin B's world-line is noninertial.

    If a student introduced the "view" of the traveling twin, the first thing I would address would be that we shouldn't naively imagine that people get an instantaneous visual snapshot of all of space at a particular time.

    If the student instead phrased this in terms of frames of reference, then there are multiple ways of going with this. Some would involve discussing multiple frames for the traveling twin. Another approach would involve discussing accelerated frames of reference -- which SR can handle just fine. Or one could point out that a frame of reference is defined operationally as the end result of a sophisticated process of surveying and signaling, and explore the result of exchanges of signals between the twins.

    There are many different possible pedagogies for SR, and many ways of formulating and resolving questions such as these. In less mathematical treatments, a common method, which I don't like much, is to focus a lot on the ##\gamma## factor and time dilation and length contraction. This is a poor approach, because ultimately SR is not reducible to time dilation and length contraction -- if it were, then the Lorentz transformation would reduce to a change of units, with no observable consequences. If one does use this pedagogy, then frames of reference take on an important role, and the twin paradox is apt to be particularly confusing for students. Laurent's Introduction to Spacetime is an example of an approach in which frames of reference are barely mentioned, and the issues involved in the twin paradox basically never even arise.
     
    Last edited: Nov 12, 2015
  16. Nov 12, 2015 #15

    mfb

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    In other words, its velocity in the reference frame of Earth is 0. You used a reference frame.
    So its velocity in the reference frame of Earth is non-zero, and changes its sign at some point. Again, the description uses a reference frame.
    While that is right, you can certainly calculate where each object is at every point in time. The sudden change of this calculation result if you change your velocity can be surprising.
     
  17. Nov 12, 2015 #16

    OmCheeto

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    Ah ha!

    After about 16 perusals of different expertplainations, I think I've discovered, at least for me, why I never "got" any of the explanations.
    There are too many correct explanations.

    I recall a thread where Drakkith, Bandersnatch, and I, were all trying to explain something to a newb, but were all using different models. I'm quite sure that we all thought the other person mansplaining was quite daft.

    pfoogle, pfoogle, pfoogle

    Energy conversion in a hydroelectric dam


    I think we'll just have to work this out for ourselves.

    hmmmm.....

    John and I may be on to something.....

    Baez.and.OmCheeto.drew.the.same.conclusive.pictue.jpg

    :smile: :-p
    In all seriousness, I have no idea why John's image looks so much like mine.
    But I suspect that it would help if you and I would work out the problem one day.
    Do you want to be Stella, or Terence?
     
  18. Nov 12, 2015 #17

    OmCheeto

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    ps. In retrospect, I now hate John.......

    Pop-science treatments sometimes ask us to imagine an army of observers, all equipped with clocks and rulers, and all at rest with respect to the given reference frame. With their clocks and rulers...

    It sounds like he was describing my "Euclid and Einstein" observational post.

    I thought it was brilliant!
    grrrrrrr............

    But, anyways, back to the chalkboard. :smile:
     
  19. Nov 12, 2015 #18

    OmCheeto

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    pps.

    Never give up, trying to understand, the un-understandable:

    [ref: The water battery [pf]]
     
  20. Nov 12, 2015 #19

    bcrowell

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    Not true. The fact that twin A stayed on earth is simply a statement that twin A's world-line coincides with the world-line of the earth. This is a geometrical primitive, and I can state it even if spacetime is a plain manifold and doesn't have a metric defined on it. It's what's known geometrically as an incidence relation. Incidence relations are things like statements that a line intersects another line, a plane doesn't intersect another plane, and so on.

    Not true. In geometrical terms, the distinction between an inertial world-line and a noninertial one is that one is a geodesic and the other is not. This has nothing to do with frames of reference.

    In general, you seem to have convinced yourself that all of relativity is defined in terms of frames of reference, and that frames of reference are indispensable to it. That's just completely false. We recently had a long discussion of this: https://www.physicsforums.com/threads/are-frames-in-physics-necessary.825744/ . Although we had a lot of back and forth about how important and useful frames were (and I changed my mind myself on some points), nobody tried to argue that relativity *required* frames of reference. That would be an untenable position.
     
  21. Nov 12, 2015 #20
    If my twin brother who went into space and lived in a condition like that on earth is alive to get back down here, there is no way why I can confirm that he is younger than me; because he e.g -born in 1980 - went into space in 1995 and lived there for 20 years, now he comes back here in 2015, his age is still the same as mine (35).
     
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