- #1
fbs7
- 345
- 37
Hello!
I had this doubt when I was 14-15 years old, and I waited for many years (I'm 49 now) to ask about it, as I always thought this to be a silly question.
In case someone can help with this, that's a thought experiment. It starts with this: if you have a sphere of gas, and then apply pressure on its surface, then the thing will heat up. Whatever gas, it will heat up, and that's because of pV = nRT, right? It doesn't matter how much time it takes - the only way that the sphere of gas under a huge pressure to have a certain volume V, is by having a high temperature.
So, if you have a sphere of any gas, if you keep putting weight on it, it doesn't matter how slow that is done, the gas will heat up and ignite a star, there's no way around that.
Now, assume I have a lot of blocks of say solid carbon, and then I slowly put them together. There will be some heating due to friction, but if I do that slow enough, the heat will dissipate, as as far as I know solid carbon under huge pressure will not be required to have a big temperature in order to have a certain volume -- it can well be at say -200F.
So, if I keep doing that slow enough, I'll accumulate a huge weight of carbon, but the center will still be cold, and therefore it will not ignite -- although I think eventually, with enough weight, the center will become some sort of degenerate matter, or even a black hole.
Is this true? That is, a huge, huge solid planet will not necessarily become a star, even if its mass becomes closer to (or perhaps even exceeds) the Sun's?
Yeah, I know, it's a silly question. I wondered about it at that age, when I was dreaming of becoming a sci-fi writer, and thought of a sunless shell planet, heated up by a small star in its very center. Yeah, that would have been a silly story, but just think of the visuals :)
I had this doubt when I was 14-15 years old, and I waited for many years (I'm 49 now) to ask about it, as I always thought this to be a silly question.
In case someone can help with this, that's a thought experiment. It starts with this: if you have a sphere of gas, and then apply pressure on its surface, then the thing will heat up. Whatever gas, it will heat up, and that's because of pV = nRT, right? It doesn't matter how much time it takes - the only way that the sphere of gas under a huge pressure to have a certain volume V, is by having a high temperature.
So, if you have a sphere of any gas, if you keep putting weight on it, it doesn't matter how slow that is done, the gas will heat up and ignite a star, there's no way around that.
Now, assume I have a lot of blocks of say solid carbon, and then I slowly put them together. There will be some heating due to friction, but if I do that slow enough, the heat will dissipate, as as far as I know solid carbon under huge pressure will not be required to have a big temperature in order to have a certain volume -- it can well be at say -200F.
So, if I keep doing that slow enough, I'll accumulate a huge weight of carbon, but the center will still be cold, and therefore it will not ignite -- although I think eventually, with enough weight, the center will become some sort of degenerate matter, or even a black hole.
Is this true? That is, a huge, huge solid planet will not necessarily become a star, even if its mass becomes closer to (or perhaps even exceeds) the Sun's?
Yeah, I know, it's a silly question. I wondered about it at that age, when I was dreaming of becoming a sci-fi writer, and thought of a sunless shell planet, heated up by a small star in its very center. Yeah, that would have been a silly story, but just think of the visuals :)