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PeterDonis's Recent Activity

  1. PeterDonis replied to the thread I Will a spring extend more when going at relativistic speeds?.

    A number of off topic posts have been deleted. Since the thread has run its course and the OP has expressed satisfaction with the...

    Jul 21, 2018 at 7:29 PM
  2. PeterDonis replied to the thread I Will a spring extend more when going at relativistic speeds?.

    Thread closed for moderation, since it looks like the OP question has been answered and the thread is now bogged down in an off topic...

    Jul 21, 2018 at 7:26 PM
  3. PeterDonis replied to the thread B Bell's Spaceship Paradox & Length Contraction.

    How you imagined which scenario? If you have a single long rocket that doesn't stretch, that's not the same scenario as the Bell...

    Jul 21, 2018 at 4:09 PM
  4. PeterDonis replied to the thread I Relativistic formula for motion in constant acceleration.

    Yes? How may I help you? Please speak slowly and clearly into the microphone. :wink: How are you deriving this formula? The way I...

    Jul 21, 2018 at 1:06 PM
  5. PeterDonis replied to the thread I How is Dark Matter Needed?.

    The velocity of what? Consistent with what observed data? Note that if you're calculating the velocity of the solar system around the...

    Jul 21, 2018 at 12:50 PM
  6. PeterDonis replied to the thread B Meaning of Wave Function Collapse.

    If you think someone's posts are violating PF rules, you should report it, not try to admonish them in the thread.

    Jul 21, 2018 at 11:51 AM
  7. PeterDonis replied to the thread B Do Quantum Fields Move?.

    Who said QFT was "spacetime independent"? I said it was frame independent. Big difference. You don't. And I don't think your...

    Jul 20, 2018 at 7:39 PM
  8. PeterDonis replied to the thread B Do Quantum Fields Move?.

    Neither of the points of view you describe are correct.

    Jul 20, 2018 at 5:14 PM
  9. PeterDonis replied to the thread B Do Quantum Fields Move?.

    You don't have to. You can describe a spacetime without choosing a frame of reference. You just have to write everything in terms of...

    Jul 20, 2018 at 4:47 PM
  10. PeterDonis replied to the thread B Do Quantum Fields Move?.

    Which background spacetime you assume in your model. Usually it's flat Minkowski spacetime, but you can do QFT on any background...

    Jul 20, 2018 at 4:19 PM
  11. PeterDonis replied to the thread B Are electrons virtual particles?.

    Not only that, this is a pop science book, not a textbook or peer-reviewed paper. You can't learn science from a pop science book. Even...

    Jul 20, 2018 at 1:15 PM
  12. PeterDonis replied to the thread B Bell's Spaceship Paradox & Length Contraction.

    No, because, as I'm understanding your description, both suspension points of the hammock would be at the same height in the ship, so...

    Jul 19, 2018 at 9:17 PM
  13. PeterDonis replied to the thread B Bell's Spaceship Paradox & Length Contraction.

    Again, see the FAQ entry I linked to, it discusses precisely this point.

    Jul 19, 2018 at 7:12 PM
  14. PeterDonis replied to the thread B Bell's Spaceship Paradox & Length Contraction.

    No, it isn't, it stays the same length. What shortens is the unstressed length of the thread. See the FAQ entry I linked to.

    Jul 19, 2018 at 7:12 PM
  15. PeterDonis replied to the thread B Bell's Spaceship Paradox & Length Contraction.

    This is my intepretation of the OP's intent. But you are right that in any relativity problem, it's better not to leave this up to...

    Jul 19, 2018 at 7:11 PM