https://en.wikipedia.org/wiki/Schwarzschild_radius
Their gravity isn't special, compared to a really large star (which is what most of them started as)....it's still just gravity.
Quote from: Testy Calibrate on March 13, 2017, 04:32:49 PMhttps://en.wikipedia.org/wiki/Schwarzschild_radiusThis is a good description, but it only describes what a black hole is in theory (and it's not the best description I've seen.....Ty, you understand the concept of escape velocity? It's simply how fast something needs to be going to escape the gravitational pull of a large mass, like a planet or star. The escape velocity of earth is about 11 km/s. Once something gets big and dense enough that the escape velocity is equal to or greater than the speed of light, it becomes a black hole The math isn't terribly difficult as a first approximation, but it's also not really that important. Now, Black holes only 'grow' when they suck in more matter, because it adds to the effective mass of the black hole. However, it's not just a simple matter of matter falling into a black hole like an object falling to earth. Because of the tremendous forces involved, matter gets accelerated, heated, and generally fucked about such that only a portion of the matter approaching the black hole actually 'goes in'. Much of it is turned to high energy plasma and goes jetting off into space. (This is how we can actually see most black holes). And black holes in the absence of immediate matter to 'feed' on hypothetically can 'evaporate' (for lack of a better term) via Hawking radiation. And keep in mind, the only reason black holes are 'scary/ is because they are so small, relatively speaking. Their gravity isn't special, compared to a really large star (which is what most of them started as)....it's still just gravity.
Would it be accurate to say that black holes are actually bodies, and not regions? Also, given the nature of the black hole's propensity to just grow and grow, will the universe eventually just be black holes that haven't collided with each other (yet) or would heat death occur before black holes can absorb everything?
Quote from: tysixtus on March 14, 2017, 06:49:10 AMWould it be accurate to say that black holes are actually bodies, and not regions? Also, given the nature of the black hole's propensity to just grow and grow, will the universe eventually just be black holes that haven't collided with each other (yet) or would heat death occur before black holes can absorb everything? The appearance of a collapsed star (the singularity) is black because gravity is so strong even light is bent so hard it can't be viewed anymore. It's not a hole, that's just a description. It's a very strong gravity region, because a large star is compressed down to the size of slightly larger than an atom. (theoretical, nobody actually knows the size)The region where light can not escape is considered the size of the "hole".And yes, eventually the entire Universe will be black holes, but even they emit radiation (Hawking radiation) so they will eventually disappear as well, leaving a cold nothing for all eternity. (theoretical)This will happen a very long time after everybody is dead, so don't worry too much about it.
Also, if a black hole presents a region so strong that nothing can escape, how can anything radiate from it, or how can plasma jet from it?
But to press further, there is an object in there somewhere, right? It sounds like "Black Hole" describes a collection of things: an object of incredible density, surrounded by a region from which nothing can escape because of gravity. Is this correct?
Cool. But to press further, there is an object in there somewhere, right? It sounds like "Black Hole" describes a collection of things: an object of incredible density, surrounded by a region from which nothing can escape because of gravity. Is this correct?
Is there a good book on all of this I can read, that is not too over-the-top?
Quote from: tysixtus on March 14, 2017, 08:33:19 AMIs there a good book on all of this I can read, that is not too over-the-top? E=mc2 is a fun and very interesting book, that covers black holes as well as almost everything else involving E=mc2https://www.amazon.com/mc2-Biography-Worlds-Famous-Equation/dp/0425181642
Quote from: F X on March 14, 2017, 07:37:15 AMQuote from: tysixtus on March 14, 2017, 06:49:10 AMWould it be accurate to say that black holes are actually bodies, and not regions? Also, given the nature of the black hole's propensity to just grow and grow, will the universe eventually just be black holes that haven't collided with each other (yet) or would heat death occur before black holes can absorb everything? The appearance of a collapsed star (the singularity) is black because gravity is so strong even light is bent so hard it can't be viewed anymore. It's not a hole, that's just a description. It's a very strong gravity region, because a large star is compressed down to the size of slightly larger than an atom. (theoretical, nobody actually knows the size)The region where light can not escape is considered the size of the "hole".And yes, eventually the entire Universe will be black holes, but even they emit radiation (Hawking radiation) so they will eventually disappear as well, leaving a cold nothing for all eternity. (theoretical)This will happen a very long time after everybody is dead, so don't worry too much about it.Cool. But to press further, there is an object in there somewhere, right? It sounds like "Black Hole" describes a collection of things: an object of incredible density, surrounded by a region from which nothing can escape because of gravity. Is this correct?
You are welcome! My copy is falling apart, I have read it a dozen times. I hope you enjoy it.
The problem with that is, a lot of narrators are pretty good and put me right to sleep, and I end up missing half the book.
Quote from: F X on March 14, 2017, 09:13:52 AMYou are welcome! My copy is falling apart, I have read it a dozen times. I hope you enjoy it.Most of my "reading" is now done via audiobook, at least leisure reading. I spend about 2.5 hours a day commuting, but I can't read in a moving vehicle (train, plane, bus, you name it). I get immediately sick. So I have to listen to everything. The problem with that is, a lot of narrators are pretty good and put me right to sleep, and I end up missing half the book.