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I What would happen if I were 1 ly from a black hole merger?

  1. Jun 26, 2017 #1
    I was reading about the latest black hole merger discovered by LIGO.


    The article states that the deflection of the arms over 4km was 1×10^-18 meters for an event 3 billion light years (ly) away. If I assume that gravitational waves follow the inverse square law, then at 1 ly the deflection would be 9 meters over the same 4km. More importantly to me, it would be about 4mm over my 1.8 meter height. I would think that would be highly unpleasant!

    Worse, at 0.1 ly the effect would be 100 times greater so I would stretch 0.4 meters. Not going to survive that!

    So, is my math correct?
  2. jcsd
  3. Jun 26, 2017 #2


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    Staff: Mentor

    That's an interesting question. If I understand things correctly, this "compression" and "expansion" are opposed by the molecular bonds making up your body, explaining why the LIGO experiments often talk about the strain of their detectors. Alas I'm not actually sure what would happen. Perhaps curling up into a ball would help?
  4. Jun 26, 2017 #3
  5. Jun 27, 2017 #4
    How much is eardrum deflected by 1 db sound?
  6. Jun 27, 2017 #5

    stefan r

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    Gold Member

    If space time is distorted would the pitch oscillate? For instance "middle a" tone would shift to A sharp and A flat/G sharp? The change might be too fast to register in the brain.

    Temperature is based on vibrations in molecular bonds. I would expect a distortion oscillation of space could alter the effective temperature. I am not sure that hot cold and back to normal at light speed would change anything. Just speculation but maybe something that was super cooled and ready to freeze or super heated and ready to boil might make the phase transition. Might also effect the activation energy for some chemical reactions. The probability of tunneling events?
  7. Jun 28, 2017 #6
    Will it be isotropic ? Or concentrated in the merger plane ??
    Be nasty if there's a planar jolt plus a polar outburst...
  8. Jun 28, 2017 #7

    stefan r

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    My post was wrong. If time and space oscillate the both the hairs in the cochlea and the sound wave will oscillate. The hair(s) that registers the note "A" will still resonate in all parts of the gravity wave. Would not hear anything odd.
  9. Jun 28, 2017 #8


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    I seem to recall that the deflection follows a 1/r relationship, not the 1/r2.

    Oh -you have already noted that in #3
  10. Jun 29, 2017 #9
    I extrapolated to 1 million km and got 28 mm for LIGO and about 13 micrometers for me. Clearly I am pushing the math here not to mention ignoring General Relativity. But still, the amazing thing is that 2 solar masses were converted to gravitational energy and the effect is so small. Gravity truly is weak!
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