SDK wrote:We can't make it too small though - it is going to be absorbing material on its journey through the Earth, and any material it does absorb will slow it down equal to that material's momentum. So it's got to be big enough that it can actually have enough speed to reach the other side.
And you do need it to absorb material, because if you don't, you have an impact. I'm not sure that's even possible (to avoid an impact by absorbing material as you approach), but if you don't avoid impact, all your kinetic energy is lost to the resulting explosions.
Or is it just the case that black holes cannot impact anything in the traditional sense since explosions can't leave the black hole anyway? Is that what I'm missing?
I think mainly what you're missing is how much denser a small black hole is compared to anything familiar.
A 1 cm2
hole through the Earth contains about 7000 tonnes of material. A black hole that size has a radius of 10-20
meters. Its gravity at a distance of 5mm is 0.01g
, so it won't actually be pulling in anything that far away. It won't even pull in everything it affects with stronger gravity than Earth's, because at that size other forces greatly outweigh gravity. But even if we assume it sucks in everything from the region where it's gravity is higher than 1g
, that's only 1/100th of the mass of the black hole itself, so it won't have a significant effect on its speed. Start it off about 1% higher than escape velocity and it'll have about escape velocity when it comes out the other side.
Unless stated otherwise, I do not care
whether a statement, by itself, constitutes a persuasive political argument. I care whether it's true.
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