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I read that gravitational waves are so tiny that we need extremely precise equipment to detect them. I am no physicist, but GR really intrigues me and I was wondering about two things:

  • How powerful would a gravitational wave have to be for an average human to notice its effects, and what would those effects look like? How would these effects change as a function of the energy of the wave?
  • What kind of cosmic event (e.g. black hole on black hole collision) could cause these gravitational waves?
knzhou
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GuPe
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    We have actually already observed gravitational waves: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102 and indeed it was colliding black holes. – aquirdturtle Jul 21 '16 at 22:01

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The gravitational waves observed recently came from the most powerful sources of such waves currently available for observations - collisions of black holes. They still were detectable with great difficulty and aid of powerful, precise equipment. Conclusion is as follows: Apparently there currently exist no gravitational waves so powerful that they could be noticable by a human. One could speculate that much stronger effects of gravity take place in interior a of black holes or very far in the past, when the universe was very hot and dense. But it doesn't seem likely that we will ever be able to observe these thing with our eyes.

Blazej
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    But in the hypothetical case there was, how big would the black holes have to be? – GuPe Jul 21 '16 at 22:57
  • You can figure it out. Assume it scales like m/r. The ones we just barely detected in 2015 were a total of 65 solar masses (total of the 2 black holes with collided), and were 1.3 billion light years away. We detected motion of about I think 1 % of a proton (look it up in wiki, I might have the order of magnitude not exactly right). I think it was like 1 part in 10^11 (please look up) stress. How much stress could you feel? It s not at light freqs, but more at sound freqs. – Bob Bee Jul 22 '16 at 05:39
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Well it depends upon size of the event, and its distance from earth. If the same event that LIGO captured, had taken place a couple of light years from earth, it would have been observed much easily, may be by human beings without any instrument. But that could have also caused other hazardous effects which is not the point here. So, it is energy, and distance to origin both are important.

kpv
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