Post by MugiwaraBlair on Oct 22, 2016 6:43:06 GMT
I Love Science
Posted: March 31, 2012 07:09 by MugiwaraBlair , 4 votes
Mind Screw In Space ( Working Title )... Greetings ! In this story we're gonna talk about..no wait, I'm gonna talk, you just listen. So I'm gonna talk about black holes, because I love black holes ( that came out wrong ). I'll try to make this coherent, intelligible and kept simple, maybe even too simple at times, but no matter because obvious statements are funny ( or at least mine should be ). For those who don't know me ( or not too well ), I'm not an astrophysicist, I'm not even a professional scientist, what I do am ( that sounds funny ^^) is a donut baker, who happens to be a pretty damn smart bookworm. So, to start off ( and in my effort to make this intelligible to the most people possible ) we'll go over how black holes form in the 1st place, from stars, so I'll begin with stars before going into black holes. It's gonna start for real now.
Stars work by atomic fusion, which means they fuse atoms together ( duh#1 ). How do they do that ? By being hot, literally hot, not smexy hot. Why are they hot ? Because they're formed by gas clouds being compressed by gravity, which makes the atoms rub together and heat up from the friction. That extreme heat inside stars make the atoms move around really fast and they fuse when they hit another atom. How does that work ? Heat is the kinetic energy of moving particles, which means hotter=faster, and stars are so hot that the atoms inside them move too fast to repel each other with electromagnetic repulsion ( that same stuff that stops matter from phasing through other matter, i.e. makes stuff feel solid *ask in a comment if you want details on that* ). The particular kind of atom stars fuse is hydrogen, why hydrogen ? Because it's very common and being the lightest element, is also the one it's most easy to start fusion with. When 2 hydrogen atoms fusing together makes a lot of energy and an helium atom. We can do it too ! It's how nuclear plants ( and atom bombs ) work, except we need a big bunch of structures and loads of money and stars only need their own mass. While "alive" , stars keep themselves stable with 2 things : the energy from fusion pushes outwards and gravity pushes inwards, basically it's like they're trying to explode and implode at the same time, and it cancels out. The astute reader might see an eventual problem with all this : Stars don't have infinite hydrogen, so what happens when they're out ? Answer in paragraph 3.
Helium being heavier than hydrogen, the core of the star compresses further, which increases pressure, which results in more friction, which means more heat, until it's hot enough to fuse helium into heavier elements, like carbon ( little parentheses, note that only the core does that at 1st, the outer shell(s) still fuses hydrogen, and in doing so accumulates enough kinetic energy to expand away from the core, this results in a red giant ) and then the same happens to carbon, core compresses, heats up, heavier atoms fuse into even heavier ones in a vicious cycle until the core becomes iron. Remember when I said fusion *makes* energy ? Well it doesn't if the atoms are too heavy, and that "too heavy limit" is at iron,beyond that it uses energy instead of making it. So now that the core doesn't produce energy anymore what happens ? The star's energy came from gravity originally, so gravity will give it energy now right ? If it's massive enough yes, but let's put that on hold for now ( keeping the best for last ). What happens if it's NOT heavy enough ? Well then that depends. If it was a really "light" star, it won't ever even become a red giant, it's outer shell will compact into the core instead of expanding, thus becoming a blue dwarf, in theory. In practice it would take such a star hundreds of billions of years to reach that point, and the universe only being about 13.7 billions years old, that theory isn't quite completely verifiable yet. If it was a "medium" star ( like the sun ), it does go red giant, and then then outer layers shed off and become planetary nebulas when the core has become iron. It can't support itself with fusion because it's not massive enough for gravity to give it the necessary input, so it compresses into a white dwarf ( previously mentioned blue dwarfs will eventually cool down to this state ) which itself will cool down into a black dwarf ( big iron sphere floating in space lol ) after trillions of years. For the curious, yes, those are very dense, like a cup=the himalaya kind of dense. If the star is really massive though, it exhausts it's hydrogen much faster ( because more mass=more pressure=more heat=more fusion ). When it's core has turned into iron, the star has become a red supergiant ( or hyper giant if it was even more massive ) and it has multiple strates ( shells on top of shells ) made of the about first 25 elements. At this point the core is so hot that even those can fuse ( it was massive enough for gravity to give it the energy ). As you might have cleverly deduced, this results in further and further loss of energy. So when the core is making really heavy elements like gold ( yes, your jewelry was made from an agonizing body, still like it ? ) or bismuth, it continues to compress and take more mass, because it's not expanding by producing energy, it's collapsing to gain energy. If it has over 1.4 times the mass of the sun ( known as the Chandrasekhar limit ), the core compresses into a neutron star and the shells go supernova, because electron degeneracy pressure broke down. That means electrons now cling to the nuclei of atoms instead of orbiting it, which makes matter ridiculously dense, like the dwarfs from before. We call that degenerate matter. At THIS point, the star's weight is held up against neutron degeneracy pressure. If the star has 2 or 3, maybe 4 but not over 5 for some reason, beats me ( btw that's called the Tolman-Oppenheimer-Volkoff limit ), then you guessed it, neutron degeneracy pressure goes bye bye too. Another theoretical bit again, there could be quark stars, held up by quark degeneracy pressure ( btw quarks are what sub-atomic particles are made of ), maybe that's what the "over 5 suns" limit is for ? Time for another new paragraph.
And there we are finally, the meat of it, the actual ob<x>ject of this story, Black Holes. There's no degeneracy pressure of any kind now, which means particles can be at the exact same place at the exact same time, so the core collapses down to a single point ( which we call a singularity ) of infinite density, because density is mass divided by volume and black holes are...well, holes. They Divide By Zero !!!! RUN !!!! ( Also, scientific proof of what dividing by 0 does, sinkholes in reality >
If you thought the couple preceding lines were mind-screwy, I'm just getting started, black holes are peculiar things. First off, there's the event horizon, which is defined as follows : "the boundary separating points in space where there are paths pointing away from the singularity from points in space where there are none" , or alternatively, "the area where all paths pointing away are in the past". This means that inside the event horizon, things like "away" and "outwards" don't exist, a black hole doesn't have an escape velocity like other cosmic objects do ( escape velocity is the speed needed to exit the gravity of a given object, for example the earth's is 11km/s ) the event horizon does, but the singularity is inescapable because there is literally no direction in which to escape, once you pass the event horizon, the singularity is all around you, in every direction and it can only get closer. Actually, that's not quite exact, there ARE directions that point away ( or are parallel, because yes, you can't go parallel to the singularity either ), but you couldn't use them because they're in the past. That's because "inside" the event horizon, Time is a physical dimension alongside length, width and depth. This also means that in there, moving forward in time equals moving forward in space too. To make this easier to grasp, imagine you're inside a bubble, it's shrinking, and moving in any way ( even spinning in place ) makes it shrink faster. And if the borders touch you it rips you apart at the sub-atomic level.
If that wasn't enough, time slows down near it. For the sake of explanation, let's say you're falling in one and I'm watching you ( watchu want me to do ? ). Due to relativity, you won't notice time slowing down, but I will see you slow down. You would also see everything get bluer while I would see you get redder, because radiations ( light, radio, x-ray, etc ) are propagating from an area of strong gravity ( near the black hole ) to an area of weaker gravity ( not near the black hole ) relative to me and the opposite relative to you ( again, ask in a comment for details on how that works ). So, I would see you slow down more and more as you get closer to the event horizon and I would see you stop outright at the edge because since you're slowing down as you get closer, from my point of view you will take infinite time to reach it. After passing that point, well you know what would happen, singularity everywhere, no escape and all. That's supposing you're still alive though, in actuality you'd just spaghettify ( that's the real scientific term ) because the part of you going in 1st would feel more attraction than the opposite of you. This happens in all gravitational fields, like say, astronauts returning to earth, but the gravity isn't strong enough to stretch anything considerably. Black holes on the other hand will stretch you into spaghetti, hence the term. Not just you either, meteors, planets and stars stretch too, even atoms deform. On top of that, the previously mentioned blue shifting means that all radiation are energized as their frequencies increase, which makes them deadlier(er). Another odd thing is if you were orbiting a black hole ( which itself invokes yet another oddity, things orbiting them HAVE TO, they're not just attracted, space is deformed so any moving object will orbit if caught regardless of it's mass ) you could see your backside.
Posted: March 31, 2012 07:09 by MugiwaraBlair , 4 votes
Mind Screw In Space ( Working Title )... Greetings ! In this story we're gonna talk about..no wait, I'm gonna talk, you just listen. So I'm gonna talk about black holes, because I love black holes ( that came out wrong ). I'll try to make this coherent, intelligible and kept simple, maybe even too simple at times, but no matter because obvious statements are funny ( or at least mine should be ). For those who don't know me ( or not too well ), I'm not an astrophysicist, I'm not even a professional scientist, what I do am ( that sounds funny ^^) is a donut baker, who happens to be a pretty damn smart bookworm. So, to start off ( and in my effort to make this intelligible to the most people possible ) we'll go over how black holes form in the 1st place, from stars, so I'll begin with stars before going into black holes. It's gonna start for real now.
Stars work by atomic fusion, which means they fuse atoms together ( duh#1 ). How do they do that ? By being hot, literally hot, not smexy hot. Why are they hot ? Because they're formed by gas clouds being compressed by gravity, which makes the atoms rub together and heat up from the friction. That extreme heat inside stars make the atoms move around really fast and they fuse when they hit another atom. How does that work ? Heat is the kinetic energy of moving particles, which means hotter=faster, and stars are so hot that the atoms inside them move too fast to repel each other with electromagnetic repulsion ( that same stuff that stops matter from phasing through other matter, i.e. makes stuff feel solid *ask in a comment if you want details on that* ). The particular kind of atom stars fuse is hydrogen, why hydrogen ? Because it's very common and being the lightest element, is also the one it's most easy to start fusion with. When 2 hydrogen atoms fusing together makes a lot of energy and an helium atom. We can do it too ! It's how nuclear plants ( and atom bombs ) work, except we need a big bunch of structures and loads of money and stars only need their own mass. While "alive" , stars keep themselves stable with 2 things : the energy from fusion pushes outwards and gravity pushes inwards, basically it's like they're trying to explode and implode at the same time, and it cancels out. The astute reader might see an eventual problem with all this : Stars don't have infinite hydrogen, so what happens when they're out ? Answer in paragraph 3.
Helium being heavier than hydrogen, the core of the star compresses further, which increases pressure, which results in more friction, which means more heat, until it's hot enough to fuse helium into heavier elements, like carbon ( little parentheses, note that only the core does that at 1st, the outer shell(s) still fuses hydrogen, and in doing so accumulates enough kinetic energy to expand away from the core, this results in a red giant ) and then the same happens to carbon, core compresses, heats up, heavier atoms fuse into even heavier ones in a vicious cycle until the core becomes iron. Remember when I said fusion *makes* energy ? Well it doesn't if the atoms are too heavy, and that "too heavy limit" is at iron,beyond that it uses energy instead of making it. So now that the core doesn't produce energy anymore what happens ? The star's energy came from gravity originally, so gravity will give it energy now right ? If it's massive enough yes, but let's put that on hold for now ( keeping the best for last ). What happens if it's NOT heavy enough ? Well then that depends. If it was a really "light" star, it won't ever even become a red giant, it's outer shell will compact into the core instead of expanding, thus becoming a blue dwarf, in theory. In practice it would take such a star hundreds of billions of years to reach that point, and the universe only being about 13.7 billions years old, that theory isn't quite completely verifiable yet. If it was a "medium" star ( like the sun ), it does go red giant, and then then outer layers shed off and become planetary nebulas when the core has become iron. It can't support itself with fusion because it's not massive enough for gravity to give it the necessary input, so it compresses into a white dwarf ( previously mentioned blue dwarfs will eventually cool down to this state ) which itself will cool down into a black dwarf ( big iron sphere floating in space lol ) after trillions of years. For the curious, yes, those are very dense, like a cup=the himalaya kind of dense. If the star is really massive though, it exhausts it's hydrogen much faster ( because more mass=more pressure=more heat=more fusion ). When it's core has turned into iron, the star has become a red supergiant ( or hyper giant if it was even more massive ) and it has multiple strates ( shells on top of shells ) made of the about first 25 elements. At this point the core is so hot that even those can fuse ( it was massive enough for gravity to give it the energy ). As you might have cleverly deduced, this results in further and further loss of energy. So when the core is making really heavy elements like gold ( yes, your jewelry was made from an agonizing body, still like it ? ) or bismuth, it continues to compress and take more mass, because it's not expanding by producing energy, it's collapsing to gain energy. If it has over 1.4 times the mass of the sun ( known as the Chandrasekhar limit ), the core compresses into a neutron star and the shells go supernova, because electron degeneracy pressure broke down. That means electrons now cling to the nuclei of atoms instead of orbiting it, which makes matter ridiculously dense, like the dwarfs from before. We call that degenerate matter. At THIS point, the star's weight is held up against neutron degeneracy pressure. If the star has 2 or 3, maybe 4 but not over 5 for some reason, beats me ( btw that's called the Tolman-Oppenheimer-Volkoff limit ), then you guessed it, neutron degeneracy pressure goes bye bye too. Another theoretical bit again, there could be quark stars, held up by quark degeneracy pressure ( btw quarks are what sub-atomic particles are made of ), maybe that's what the "over 5 suns" limit is for ? Time for another new paragraph.
And there we are finally, the meat of it, the actual ob<x>ject of this story, Black Holes. There's no degeneracy pressure of any kind now, which means particles can be at the exact same place at the exact same time, so the core collapses down to a single point ( which we call a singularity ) of infinite density, because density is mass divided by volume and black holes are...well, holes. They Divide By Zero !!!! RUN !!!! ( Also, scientific proof of what dividing by 0 does, sinkholes in reality >
If you thought the couple preceding lines were mind-screwy, I'm just getting started, black holes are peculiar things. First off, there's the event horizon, which is defined as follows : "the boundary separating points in space where there are paths pointing away from the singularity from points in space where there are none" , or alternatively, "the area where all paths pointing away are in the past". This means that inside the event horizon, things like "away" and "outwards" don't exist, a black hole doesn't have an escape velocity like other cosmic objects do ( escape velocity is the speed needed to exit the gravity of a given object, for example the earth's is 11km/s ) the event horizon does, but the singularity is inescapable because there is literally no direction in which to escape, once you pass the event horizon, the singularity is all around you, in every direction and it can only get closer. Actually, that's not quite exact, there ARE directions that point away ( or are parallel, because yes, you can't go parallel to the singularity either ), but you couldn't use them because they're in the past. That's because "inside" the event horizon, Time is a physical dimension alongside length, width and depth. This also means that in there, moving forward in time equals moving forward in space too. To make this easier to grasp, imagine you're inside a bubble, it's shrinking, and moving in any way ( even spinning in place ) makes it shrink faster. And if the borders touch you it rips you apart at the sub-atomic level.If that wasn't enough, time slows down near it. For the sake of explanation, let's say you're falling in one and I'm watching you ( watchu want me to do ? ). Due to relativity, you won't notice time slowing down, but I will see you slow down. You would also see everything get bluer while I would see you get redder, because radiations ( light, radio, x-ray, etc ) are propagating from an area of strong gravity ( near the black hole ) to an area of weaker gravity ( not near the black hole ) relative to me and the opposite relative to you ( again, ask in a comment for details on how that works ). So, I would see you slow down more and more as you get closer to the event horizon and I would see you stop outright at the edge because since you're slowing down as you get closer, from my point of view you will take infinite time to reach it. After passing that point, well you know what would happen, singularity everywhere, no escape and all. That's supposing you're still alive though, in actuality you'd just spaghettify ( that's the real scientific term ) because the part of you going in 1st would feel more attraction than the opposite of you. This happens in all gravitational fields, like say, astronauts returning to earth, but the gravity isn't strong enough to stretch anything considerably. Black holes on the other hand will stretch you into spaghetti, hence the term. Not just you either, meteors, planets and stars stretch too, even atoms deform. On top of that, the previously mentioned blue shifting means that all radiation are energized as their frequencies increase, which makes them deadlier(er). Another odd thing is if you were orbiting a black hole ( which itself invokes yet another oddity, things orbiting them HAVE TO, they're not just attracted, space is deformed so any moving object will orbit if caught regardless of it's mass ) you could see your backside.
