5 ms·

Total (unqualified) spitballing, but wouldn't a black hole "bullet" that hit the Earth experience effectively 0 frictional losses? By definition it won't be pus

Total (unqualified) spitballing, but wouldn't a black hole "bullet" that hit the Earth experience effectively 0 frictional losses? By definition it won't be pushing stuff out of the way, so it seems like an inbound black hole would punch right through the Earth. Local gravity is probably going to be quite nasty during the transit, but beyond that, it seems like a fairly survivable event.

nine_k 7y ago
Won't it pull some of the matter it passes through under the event horizon? The extremely curved spacetime will likely turn rock to dust in near vicinity. Then, as the mass grows, so would the gravitational pull, while the speed relative to the planet being punctured would lower due to conservation of momentum. If the tiny bullet-class black hole makes it through a planet, it could gain significant additional mass, and leave quite an exit wound.
- neuronic 7y ago
  If a random PBH of 9mm traveled at near light speed through Earth, would it even pull anything into the event horizon that is not within close range of that 9mm diameter? For example, it travels through Earth and then leaves a 9mm hole throughout the planet.
  - Enginerrrd 7y ago
    No it wouldn't, but I'm thinking it would be able to transfer some kinetic energy to the earth which would be a very very bad thing.
  - perl4ever 7y ago
    I'm not good at physics, but it seems to me if this 9mm object had the mass of earth, then at a distance of about 6400 km it would exert 1G, and at minimal distance, it would exert about a zillion Gs. So even assuming it didn't pull in matter per se, the gravity and tidal forces ought to destroy earth about as effectively as colliding with a regular earth sized planet.
- Retric 7y ago
  An earth’s mass black hole has a ~1cm sized event horizon. It would suck up matter several times that, but it’s not enough to gain significant mass relative to it’s size on a single pass. This stays true as you scale things down. Something in the 10^12 kg range is going to have an atomic scale event horizon so it’s not picking up significant mass as it shoots through the earth.
deeviant 7y ago
Well, do you know how we "see" black holes? The "body" of a black hole is nothing but darkness, but we see the radiation given off by the mass accelerating toward the black hole event horizon that can often reach significant fractions of c. Given the high mass density of a planet compared to space, a massive amount of hard radiation will be released. Also the relative velocities of earth and the black hole is extremely important. Depending on the relative velocities, it's possible that the blackhole simply gets lodged in the earth's core and we're 100% dead, another 100% dead scenario is if it plunges in, out the other side, but then "falls back" for another pass and so on.

nine_k 7y ago

Won't it pull some of the matter it passes through under the event horizon? The extremely curved spacetime will likely turn rock to dust in near vicinity. Then, as the mass grows, so would the gravitational pull, while the speed relative to the planet being punctured would lower due to conservation of momentum. If the tiny bullet-class black hole makes it through a planet, it could gain significant additional mass, and leave quite an exit wound.

neuronic 7y ago
If a random PBH of 9mm traveled at near light speed through Earth, would it even pull anything into the event horizon that is not within close range of that 9mm diameter? For example, it travels through Earth and then leaves a 9mm hole throughout the planet.
- Enginerrrd 7y ago
  No it wouldn't, but I'm thinking it would be able to transfer some kinetic energy to the earth which would be a very very bad thing.
- perl4ever 7y ago
  I'm not good at physics, but it seems to me if this 9mm object had the mass of earth, then at a distance of about 6400 km it would exert 1G, and at minimal distance, it would exert about a zillion Gs. So even assuming it didn't pull in matter per se, the gravity and tidal forces ought to destroy earth about as effectively as colliding with a regular earth sized planet.
Retric 7y ago
An earth’s mass black hole has a ~1cm sized event horizon. It would suck up matter several times that, but it’s not enough to gain significant mass relative to it’s size on a single pass. This stays true as you scale things down. Something in the 10^12 kg range is going to have an atomic scale event horizon so it’s not picking up significant mass as it shoots through the earth.

deeviant 7y ago

Well, do you know how we "see" black holes? The "body" of a black hole is nothing but darkness, but we see the radiation given off by the mass accelerating toward the black hole event horizon that can often reach significant fractions of c. Given the high mass density of a planet compared to space, a massive amount of hard radiation will be released. Also the relative velocities of earth and the black hole is extremely important. Depending on the relative velocities, it's possible that the blackhole simply gets lodged in the earth's core and we're 100% dead, another 100% dead scenario is if it plunges in, out the other side, but then "falls back" for another pass and so on.