A Bit About Black Holes

Hello all;

Today I'm going to tell you a few things about black holes that you may not know. For convenience I'm going to assume you know what a black hole is. If you don't, NASA is a good place to start.

It is certainly possible to orbit a black hole. It is possible in theory to orbit a black hole and achieve faster than light velocities.

Black holes must radiate energy. Why? Entropy. Let's say I throw a bunch of matter with a lot of different particles and energy (like an alien civilization) into a black hole. Once all that matter is in there, it is impossible to determine it's state. You can't get info out of a black hole, so it is impossible to determine the amount of entropy the matter inside has. This is the same as decreasing the total amount of entropy in the universe, which is frowned on by the Second Law of Thermodynamics. Thus, in order to keep the total entropy of the universe increasing, black holes must radiate some energy, though admittedly in very small quantities.

The enormous pressures of the big bang could have produced small, 'primordial' black holes. If any are still around, they would now be so cold it would be very difficult to detect them.

It is thought that binary black holes may exist. This is where two black holes orbit each other. If they do, the massive amounts of gravity being thrown around would produce gravity waves strong enough to detect. Currently, we have no idea if gravity waves even exist because it's very hard to find one strong enough to show up on sensors, even in principle.

Gravity travels at the speed of light. If you could accelerate two black holes to faster than the speed of light and crash them into each other, they would pass through each other and continue on their way  before gravity could pull them together. Now, it's highly unlikely that people will ever have the machinery to do this. However, in the enormous convulsions of the big bang, it is possible this may have occurred with some primordial black holes. If this ever happened it would likely leave a 'wormhole' behind.


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