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Comment by mirimir | Hacker News Reader

In the reddit AMA, DW wrote:

> Myself and one of my supervisors had a conversation about this a few weeks ago. We did some calculations which suggest that if you were in a space-ship close to the merging black holes you would feel a force which was pretty comparable to the force you feel by standing next to a loudspeaker at a music concert. You'd feel a vibration travelling through your body, but we were pretty confident it wouldn't hurt you!

Maybe the gravitational waves wouldn't hurt, but the gammas etc would be painful. I'm reminded of Greg Egan's Diaspora.

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Assuming no accretion disks, there wouldn't be any em radiation as far as I know. Where would it come from?

Thanks. I see now that it's merging binary neutron stars that create the huge gamma spikes.[0]

[0] https://www.astro.cf.ac.uk/research/gravity/tutorial/?page=4...

Edit: That tutorial also explains that black holes are very simple objects, so the chirps and ringdowns are likewise very simple. So black hole masses can be calculated very precisely. Also, amazingly:

> Just as optical radiation and radio waves, the luminosity of gravitational radiation falls off in inverse proportion to the square of the distance from the source. This makes binary black hole inspirals standard sirens: if we know what the masses of the two black holes are then we can infer the distance to the source by measuring its apparent luminosity. We can precisely measure the masses because the rate at which the frequency and amplitude of an inspiral increases depends only on the masses.

I doubt that the merger was converting all energy into GW. I suppose there might be some effects occurring at such high energy that we don't have precise simulation of what would be emitted.

In any case, that emitted energy certainly wouldn't be good for any living tissue. I don't think you could expect to witness a black hole merger from the comfort of your spaceship a few thousands of miles away.

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