system
Given the following post, respond as if you're commenting on Reddit:
human
If I had a spaceship and traveled in a straight line - would I hit a black hole sooner or later? Would I be even able to detect if I am not flying straight into one?

Let's assume that time is not important and that my speed is very high. We can imagine it as some sort of a "space jump" like in Star Trek - how would the spaceship even know if it is not flying straight to death? Is the universe so big that it has enough black holes so that the ship would hit a black hole sooner or later?

b) How could I even detect that I am not flying straight into a black hole - I know most of them can be detected because they are eating up stuff, but are there real "black" black holes?

c) part of this question is changing the black hole for a star -> obviously a star can be seen and detected easily; but is the universe so vast, that a spaceship flying straight through it would hit a star sooner or later?

I also know that flying straight in space can be pretty hard, but let's assume that my spaceship can do this.
gpt
No, in fact it's almost incomprehensibly unlikely that you'd hit a black hole. Black holes are very rare and very tiny.

In fact it's incredibly unlikely that you'd ever hit anything at all.

This gets into something called "Olbers' paradox." It's a simple proposition: If the universe is infinite, doesn't every possible ray drawn from any point eventually intersect the surface of a star?

The answer is no, because of how geometry works. If the universe were *Euclidean,* in which the distance between points is a function of nothing but the coordinates of those points, then yes, eventually all rays would intersect a star. But the universe isn't Euclidean. The distances between points are a function both of the coordinates of the points *and of time.* In particular, the distances between points *increase* with time uniformly throughout the universe.

If you *froze time* and considered the universe as a "snapshot," then yes, any ray you might draw from a chosen point would eventually intersect a star. But you can't freeze time in reality. In reality, the metric of the universe is expanding, meaning a ray that propagates away from a point at the speed of light will almost certainly *never* intersect a star.

As for the other question about how you'd notice a black hole, you'd be able to see it from light-years away. Black holes found in nature are surrounded by luminescent infalling matter that emits a ton of radiation in the X-ray band. Because of these accretion discs (as they're called), black holes tend to shine like beacons in the night.