Known Dark Matter Isn't Enough
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Known Dark Matter Isn't Enough
1–10 of 19 posts
Re: Known Dark Matter Isn't Enough
#2I like the idea of black holes being more common. If there is one close we could visit it someday and yet it doesn't pose any danger to us, since there is no chance that it is in our solar system.
Given the ratio of one black hole per 1000 stars, which is the best we can guess right now, the average distance to the closest black hole is 36 lightyears.
Re: Known Dark Matter Isn't Enough
#3Nice survey of dark matter candidates. I had not heard about the primordial black hole option.
Re: Known Dark Matter Isn't Enough
#4I like the idea of black holes being more common. If there is one close we could visit it someday and yet it doesn't pose any danger to us, since there is no chance that it is in our solar system. Given the ratio of one black hole per 1000 stars, which is the best we can guess right now, the average distance to the closest black hole is 36 lightyears.
There's a chance one might pass through, which seems very alarming to me. It also seems like we'd have observed interactions between such black holes and other stars pretty frequently.
I don't know if we'd have expected to have seen lensing effects from our whole-sky surveys, but it seems to me that this would also be probable.
Finally, if you send a line through our galaxy, you'd expect it to pass near a lot of these black holes -- and thus you'd expect to see a lot of microlensing effects which the article states don't seem to occur nearly often enough.
Re: Known Dark Matter Isn't Enough
#5I like the idea of black holes being more common. If there is one close we could visit it someday and yet it doesn't pose any danger to us, since there is no chance that it is in our solar system. Given the ratio of one black hole per 1000 stars, which is the best we can guess right now, the average distance to the closest black hole is 36 lightyears.
There's a chance one might pass through , which seems very alarming to me. It also seems like we'd have observed interactions between such black holes and other stars pretty frequently. I don't know if we'd have expected to have seen lensing effects from our whole-sky surveys, but it seems to me that this would also be probable. Finally, if you send a line through our galaxy, you'd expect it to pass near a lot of the…
I wouldn't worry myself with that. Since a black hole behaves exactly like a normal star at a large distance, the chance is very small, even if there are many of them. For example, when our galaxy merges with Andromeda there will be only ~1 star collision.
Normal black holes are really small, much smaller than a planet, which we can barely detect now. And those planets must be orbiting a star and in the correct inclination to be detected.
Re: Known Dark Matter Isn't Enough
#6I like the idea of black holes being more common. If there is one close we could visit it someday and yet it doesn't pose any danger to us, since there is no chance that it is in our solar system. Given the ratio of one black hole per 1000 stars, which is the best we can guess right now, the average distance to the closest black hole is 36 lightyears.
Black holes are relative. Inside you there is a black hole at your center of mass (its just that your event horizon is very far inside you). To things moving at relativistic speeds in relation to you, your mass is huge (to them), and you look like a black hole.
Re: Known Dark Matter Isn't Enough
#7Earlier quoted context omitted.
There's a chance one might pass through , which seems very alarming to me. It also seems like we'd have observed interactions between such black holes and other stars pretty frequently. I don't know if we'd have expected to have seen lensing effects from our whole-sky surveys, but it seems to me that this would also be probable. Finally, if you send a line through our galaxy, you'd expect it to pass near a lot of the…
I wouldn't worry myself with that. Since a black hole behaves exactly like a normal star at a large distance, the chance is very small, even if there are many of them. For example, when our galaxy merges with Andromeda there will be only ~1 star collision. Normal black holes are really small, much smaller than a planet, which we can barely detect now. And those planets must be orbiting a star and in the correct incli…
Stellar mass black holes are small in size, but supermassive black holes can be larger than our solar system. Fortunately for us they only exist in the centers of galaxies. The closest supermassive black hole to us is 30,000 light years away.
Re: Known Dark Matter Isn't Enough
#8I like the idea of black holes being more common. If there is one close we could visit it someday and yet it doesn't pose any danger to us, since there is no chance that it is in our solar system. Given the ratio of one black hole per 1000 stars, which is the best we can guess right now, the average distance to the closest black hole is 36 lightyears.
Black holes are relative. Inside you there is a black hole at your center of mass (its just that your event horizon is very far inside you). To things moving at relativistic speeds in relation to you, your mass is huge (to them), and you look like a black hole.
There is not a black hole at your center of mass. Protons and neutrons (let alone atoms) are not dense enough to form a black hole. In all likelihood, your center of mass is empty space between a nucleus and some electrons.
Re: Known Dark Matter Isn't Enough
#9Earlier quoted context omitted.
Black holes are relative. Inside you there is a black hole at your center of mass (its just that your event horizon is very far inside you). To things moving at relativistic speeds in relation to you, your mass is huge (to them), and you look like a black hole.
There is not a black hole at your center of mass. Protons and neutrons (let alone atoms) are not dense enough to form a black hole. In all likelihood, your center of mass is empty space between a nucleus and some electrons.
if you don't consider the effects of quantum mechanics then all objects have an event horizon.
Re: Known Dark Matter Isn't Enough
#10Earlier quoted context omitted.
There is not a black hole at your center of mass. Protons and neutrons (let alone atoms) are not dense enough to form a black hole. In all likelihood, your center of mass is empty space between a nucleus and some electrons.
if you don't consider the effects of quantum mechanics then all objects have an event horizon.
No- if you think about a 'classical' particle (that is, ignore quantum effects), once you are inside the particle the gravitational pull is proportional to the distance from the center.
In other words, if you are outside a spherical mass the pull of gravity gets stronger as you get closer (~1/r^2). But once you are inside the mass, the pull gets weaker. Hence there is no black hole at the center of the earth, for example.