Possibly. According to this article https://www.forbes.com/sites/startswithabang/2020/02/15/ask-ethan-could-gravitational-waves-ever-cause-damage-on-earth.

I want to add on to this question - would the answer to the above be different if the black hole had no accretion disk?

I did the math a while back- you have to be crazy close, like 100s of km, to a merger for the gravity waves to affect you directly. /u/StandardSudden1283 Even a 'cold' pair of BHs (no accretion disk) would kill you from tidal forces at a much greater distance.

The article/u/kanrith links to suggests the waves could cause earthquakes or something on the planet you're on, and so indirectly hurt you, but its not verry convincing.

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In an expanding universe things like distance and speed become ambiguous at large distances, with several sensible definitions that all give the same results under normal circumstances suddenly disagreeing. When it comes to distance, this is due to the expansion of space changing the scale of the universe while light is traveling towards us, so effectively changing things in the middle of our measurement. When it comes to speed, it is due to the difference between things moving apart because of their own motion, or things moving apart because new space appeared between them.

As a rough analogy for the former, imagine two ants separated by a piece of string they can walk along, but they're currently standing still. Now someone cuts the string and splices in a much longer piece of string between the ants. The ants didn't move, but now the distance between them (along the string = through space, in this analogy) is much longer. Does that mean the ants had a huge relative velocity when the splicing took place?

It's up to you, really, but I think most of us would prefer to factor out the expansion part and only include the moving part in the definition of velocity. In cosmology, this definition of speed is called peculiar velocity, and would not be particularly lage for two objects on opposite sides of the observable universe.

All of these complications go away if you only look at nearby objects. It's relative speed between two objects close to each other that's limited to 299792 km/s.

Firstly, 8±3 doesn't mean "it's definitely between 5 and 11". It just means "it's 68% likely that it's in that range", and then it's 95% likely that it's in the range [2:14] and 99.7% likely that it's in the range [-1:17] (really [0:17] in this case, since it can't be negative).

Secondly, why do I say that it's likely to be lower than 8% rather than higher, given that the error bars go both up and down? That's because we're looking at extreme value statistics. Put simply, we're not looking at a random data point, we're looking at the data point with the highest value. That means we're much more likely to see a positive noise fluctuation than a negative one, because a positive noise fluctuation makes a data point more likely to be the highest one while a negative noise fluctuation does the opposite.

Here's a concrete example. Let's say we have two sets of numbers, set A and set B, each with 1000 numbers in them. In set A, each number has a true value of 5 but ±1 in errors. In set B, each number has a true value of 0, but ±10 in errors. So in reality the numbers in set A are much bigger than in set B. But now look at what happens when we take errors into account. In set A, it's unlikely that we will see any numbers higher than around 8, since a +3 error has a likelihood of only 0.15%. Meanwhile, in set B we're almost guaranteed to see numbers higher than 20. So if we're not careful we will incorrectly conclude that B is really bigger than A.

Sorry, that didn't come out as clearly as I had hoped. If you know some simple programming, then I recommend just writing a 5-line program to test it out yourself.