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Final project for my AP Physics class

  1. May 7, 2008 #1
    I am working on a final project for my AP Physics class and must do some research on Relativity. I just have a few questions and was wondering if anybody could answer them for me. It would be greatly appreciated!

    1. Assuming that traveling at the speed of light were possible, "time" would stop. Does that
    imply then, that while traveling at a speed greater than light "time" would reverse?

    2. If the answer to question one happens to be yes, then what would happen when "time"
    reached zero for the moving observer? Would he cease to exist or continue to move
    back in time living with two realities?

    3. In the Twin Paradox, would the "younger" twin be physically younger, or just have
    perceived a smaller time lapse?

    If these could be answered, it would be awesome! Thank you in advance!

    -Matt
     
    Last edited by a moderator: Jan 7, 2014
  2. jcsd
  3. May 7, 2008 #2

    Dick

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    1. No. 2. That's a weird question. Now you can see why the answer to 1 is no. 3. Physically younger. "Perceived smaller time lapse" can be obtained by taking a nap on a plane flight. This is physical.
     
  4. May 7, 2008 #3
    Thank You!
    But then, I have another question...

    What would happen to "time" if observer A were to move faster than light?
     
  5. May 7, 2008 #4

    Dick

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    You are talking about "relativity" as in the "theory of relativity", right? Observers DO NOT move faster than the speed of light. That leads to causal paradox. Aside from the mundane fact that it would take an infinite amount of energy for an observer (who must have nonzero rest mass) to even reach the speed of light. There are a lot of interesting issues that you can actually talk about that can be addressed without delving into metaphysical "what if's" that the theory has no power to address. If this is a question for AP Physics, you might want to concentrate on those. For example, the "twin paradox". Why is it called a "paradox". Why is it actually not a paradox at all? If you can understand that, then you will have learned something worth reporting on. Good luck! You can do it.
     
  6. May 7, 2008 #5

    Dick

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    If stuff like this really obsesses you could also research the "pre-big-bang" in string cosmology. It hypothesizes that the universe before what we think of as the big-bang was contracting and inflationary, and that the big bang was not a true singularity (thanks to stringy effects). And the big bang was really a 'big bounce' into an expanding phase. What were the merits of the theory? What were it's drawbacks? Why is it less popular than it used to be? I can give you some pointers. I wrote some papers in that field. But I'll warn you, it'd probably be more technical than you want.
     
  7. May 8, 2008 #6
    Yes, I am talking about the "Theory of Relativity". My question, though, was based on the hypothetical. I realize that as speed approcahes that of light, relativistic mass increases as well, ultimately resulting in an infinte amount of energy being required for any object with mass to move at the speed of light. I was directing my question more to the thought behind speed, not the actual application. Thank you for your input for a more relative area of research, but my questions were in the area I desired, not the Twin Paradox.
     
  8. May 8, 2008 #7
    Look up Tachyons. With their definition you should be able to see why traveling faster than Light makes you "go back in time".
     
  9. May 8, 2008 #8
    Thank You!
     
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