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Insights Does Gravity Gravitate? Part 3 - The Wave - Comments

  1. Sep 27, 2015 #1

    PeterDonis

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  2. jcsd
  3. Sep 27, 2015 #2
    Wonderful series!
     
  4. Sep 28, 2015 #3
    Excellent summary of a subtle and somewhat non-intuitive issue. Well done :)
     
  5. Sep 29, 2015 #4

    BiGyElLoWhAt

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    I thoroughly enjoyed all 3 articles thus far. More to come? =D
     
  6. Sep 29, 2015 #5

    PeterDonis

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    Yes, but the first three were already written, since they were blog posts on the old PF blog facility. I'll actually have to write the next one. :wink:
     
  7. Sep 30, 2015 #6
    Well get to it :-)
     
  8. Oct 4, 2015 #7
    Loved ur post. Why do u think gravity can't be simulated in a lab? If we solve gravity and accurately find a graviton, do u think we then could produce gravity in a lab?
    Thanks for your help.
     
  9. Oct 4, 2015 #8

    PeterDonis

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    It doesn't have to be "simulated". We can measure the gravity of ordinary objects with very precise tools. Google for "Cavendish Experiment".
     
  10. Oct 4, 2015 #9
     
  11. Oct 4, 2015 #10
    I thought cavendish failed his peer review? So it was determined that he didn't demonstrate gravity.
     
  12. Oct 4, 2015 #11

    PeterDonis

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    Um, what? Cavendish did his original experiment in the late 1700's. There was no "peer review" then.

    Quite the contrary; Cavendish's results were accepted, because they could be used to calculate an accurate value for Newton's gravitational constant, and that value could then be plugged in to Newtonian models of the solar system and shown to match observations.
     
  13. Oct 4, 2015 #12

    PeterDonis

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    Also, Edriven, when you quote someone's post, you can put your reply in the same post, as I did in post #11 of this thread in reply to you; you don't have to put it in a separate post, as you did with posts #9 and #10 in this thread.
     
  14. Oct 4, 2015 #13
    http://www.public.iastate.edu/~lhodges/Michell.htm. I know of the Cabendish experiment. I have tried to find information on the actual experiment but find conflicting data. An experiment like this, would not seem practical to me personally. We all know that we are: rotating at 10,000mph, orbiting the sun, have barometric pressure, have seismic activity, have oceans that pull toward the moon, etc.
    This is a lot of natural forces to shield against. So from my perspective, the Cavendish experiment does not prove the force of gravity.
     
  15. Oct 4, 2015 #14

    PeterDonis

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    Can you give some specific examples?

    The experiment has been repeated multiple times with modern equipment. There is no doubt at all about the results. Here is an example of a modern setup:

    http://www.phys.utk.edu/labs/modphys/Pasco Cavendish Experiment.pdf

    All that just means you need to do the experiment under controlled conditions in a lab; that is easily done with modern equipment. It can even be done by a lay person nowadays; for an example, see John Walker's description, "Bending Spacetime in the Basement":

    https://www.fourmilab.ch/gravitation/foobar/

    You are entitled to your perspective, but that doesn't make it correct. I strongly advise looking into this in more detail before you jump to the conclusion that modern physics is wrong.
     
  16. Oct 6, 2015 #15
    Thank you for help on this topic. I don't think modern physics is wrong. I am trying to question it only to understand it further. Do you thing gravity could be particles, like neutrinos, that orbit an object with mass?
     
  17. Oct 6, 2015 #16

    PeterDonis

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    No. If you want to learn about our best current theory of gravity, I suggest taking the time to work through a good GR textbook. Sean Carroll's online lecture notes aren't a bad start:

    http://arxiv.org/abs/gr-qc/9712019
     
  18. Oct 6, 2015 #17
    Thank you for the reference
     
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