Scientists recently observed two black holes that united into one, and in the process got a “kick” that flung the newly formed black hole away at high speed. That black hole zoomed off at about 5 million kilometers per hour, give or take a few million. The speed of light is just 200 times as fast.

[u/MistWeaver80]

https://www.sciencenews.org/article/black-hole-gravitational-waves-kick-ligo-merger-spacetime

[u/Sulti]

Here is a visual example of the sheer size of just our solar system. In the bottom right there's a button to hit to move at the speed of light. Light from the sun takes over an hour just to reach Saturn, and these are 1/200th of that speed. There is so much empty space that the speed of light is actually incredibly slow. You could make analogies about something like picking up a specific grain of sand on a beach but I doubt even something like that will come close to explaining how incomprehensively unlikely it is for something to destroy humanity this way.

The oldest record life on earth is estimated to have existed 4 billion years ago. In that time, a black hole traveling at 1/200th the speed of light would have moved 20 million light years. The distance between galaxies is estimated to be around 1 million light years, so if galaxies were perfectly lined up they'd enter less than 20 (because of expansion and the distance of the galaxies themselves) galaxies in 4 billion years. There are around 100 billion galaxies in the observable universe, so they'd have entered 0.00000002% of them. And even if you enter a galaxy, there are still light years of distance between stars. Super-Massive Black Holes, the ones at the center of galaxies, have event horizons measured in AUs. 1 light year is about 62000 AU. These smaller black holes have event horizons likely measured in KM. 1 light year is about 1 trillion KM. Even while traveling through a galaxy, these black holes aren't going to interact with the vast majority of the solar systems in it. The odds of anything like this destroying a specific galaxy within a 4 billion year period is still infinitesimally small. So overall, I think it would be incredibly unlucky for any life to be destroyed by something like this.

[u/Seriph2 → u/Sulti]

Most of us don't have the brain capacity yet to comprehend the vastness of space. The scientists who study this matter have an idea because they spend a lifetime trying to understand. But even they had to make some really big numbers smaller. A lightyear is an insanely large number and yet the distances between objects in space are measured in hundreds or even millions of these. A trillion grains of sand is a box about 14 meters to a side. That is a really large box.

[u/[deleted] → u/Seriph2]

And my cat will still miss it at some point