6 ms·

If a black hole has the mass of the earth it's Schwarzschild radius would be about 9mm. If it was disturbed from an orbit well past pluto it would have quite a

by sliken 7y ago

If a black hole has the mass of the earth it's Schwarzschild radius would be about 9mm. If it was disturbed from an orbit well past pluto it would have quite a velocity when it hit earth. The good news is it would pass effortlessly through the earth and not go to the earth's core and stay there. After all where is the resistance going to come from? Now if the blackhole was brought to rest at the earth surface it wouldn't reach escape velocity (11.2 km/sec), but anything coming from way past pluto would likely have a much larger velocity. The bad news is that having an earth skewer the earth at high speed is going to cause some pretty crazy gravitational interactions. Also some of the matter falling into the black hole from earth would be consumed, but some of it would radiated out, no idea if that would be worse than the physical disruptions or not.

ehsanu1 7y ago
The collision case is screaming for a "What If"-style exposition, as in https://what-if.xkcd.com/ https://what-if.xkcd.com/
IvyMike 7y ago
To paraphrase Neal Stephenson, "The earth blew up without warning and for no apparent reason."
Zardoz84 7y ago
and wildy change Earth orbit
KiwiJohnno 7y ago
>crazy gravitational interactions Thats putting it very mildly. Its actually quite an interesting thought exercise - As this black hole approached earth its gravity would counteract earth's gravity, meaning everything near where it "touched down" would experience near zero-g as it approached. The opposite side of the earth would experience greatly increased gravitational pull... Then while the black hole was inside the earth, everything would be experiencing close to 2G, then zero G for a bit for the poor souls on the side of the earth where it exited. Because of the fantastic amount of momentum it would have, and it would certainly be travelling at well over earth escape velocity I would expect it would travel straight through earth and keep going, not even coming close to stopping inside earth. The affects on earth would be very... bad. I'd imagine it would trigger devastating global earthquakes, as well as epic rock slides from the changing gravitational forces. Not to mention the tsunamis from the oceans sloshing around like water in a giant bath, as well as all the rockslides both above and below water. It would be a mess. Assuming this object would be travelling at 100km/sec, and the gravity would maybe begin to badly affect us when it was 50,000 km out from the surface of the earth (?) then it would take about 16 hours to travel from this distance, impact the earth and then reach this distance out the other side. I'm not sure how much energy would be released by the matter being consumed by the black hole - It might not be very much, after all its total gravitational pull wouldn't be very high, but would be travelling at probably at least 50+ km/second - certainly more than 11km/sec (earth escape velocity) The matter in front of the black hole might simply be swallowed up without much fuss, or if there is any "resistance" to this matter falling down past the event horizon I'd imagine it would be like a continuous series of nuclear bombs going off as matter was flash heated to the point of spontaneous nuclear fusion before it passed the event horizon. The one good point to note in all of this is it would be extraordinarily difficult to disturb this object from its object so it fell into the inner solar system. After all, it has the same mass as earth, and we don't have to be worried about random stuff disturbing earth's orbit.
- debatem1 7y ago
  This would be an extraordinary sci-fi story and I would pay good money to read it.
  - kyralis 7y ago
    Not quite the same thing, but you might be interested in _The Forge of God_ by Greg Bear.
    - KiwiJohnno 7y ago
      I second that. Great book. The sequel, anvil of stars is pretty good too, but its a different setting
  - sliken 7y ago
    Same here, maybe even write a simulation or two to help pin down some of the side effects. I did do a super simple simulation trying to explore if you could escape from beyond the event horizon where time dilation becomes so extreme that even very rare events become common. One of those extremely rare events could be when a galaxy collides with a second galaxy and the black holes at the center end up merging. Turns out you could escape from falling into a particular black hole if you had a second black hole to counteract the gravity. Unfortunately even while you are at zero acceleration, you end up inside an even larger event horizon formed by the two black holes. Your choices would be to fall into the first black hole, fall into the second, or wait for them to collide. Even the waiting isn't a particularly good option. While being outside the event horizon of a very large black hole minimizes the spagetification problem, there's no such protection inside the event horizon. In any case if interested in reading sci-fi based on black holes check out https://en.wikipedia.org/wiki/Black_holes_in_fiction https://en.wikipedia.org/wiki/Black_holes_in_fiction
  - kevin_thibedeau 7y ago
    David Brin's Earth deals with a black hole stuck orbiting inside the planet. Also predicted Google glass backlash.
- 7y ago
intarga 7y ago
The point stands, it's not any more dangerous than an earth sized object of the same mass, in fact it's less. It isn't any easier to divert from it's orbit, it is not any more likely to collide with the earth if diverted (in fact less so on account of its small size), and it would be no more destructive on collision.
- sliken 7y ago
  If you drop the earth into the sun, the sun won't care. If you drop a black hole into the sun, the sun dies. Seems a wee bit more dangerous to me.
lumberingjack 7y ago
I read this book once.

by sliken 7y ago

ehsanu1 7y ago

The collision case is screaming for a "What If"-style exposition, as in https://what-if.xkcd.com/ https://what-if.xkcd.com/

IvyMike 7y ago

To paraphrase Neal Stephenson, "The earth blew up without warning and for no apparent reason."

Zardoz84 7y ago

and wildy change Earth orbit

KiwiJohnno 7y ago

>crazy gravitational interactions Thats putting it very mildly. Its actually quite an interesting thought exercise - As this black hole approached earth its gravity would counteract earth's gravity, meaning everything near where it "touched down" would experience near zero-g as it approached. The opposite side of the earth would experience greatly increased gravitational pull... Then while the black hole was inside the earth, everything would be experiencing close to 2G, then zero G for a bit for the poor souls on the side of the earth where it exited. Because of the fantastic amount of momentum it would have, and it would certainly be travelling at well over earth escape velocity I would expect it would travel straight through earth and keep going, not even coming close to stopping inside earth. The affects on earth would be very... bad. I'd imagine it would trigger devastating global earthquakes, as well as epic rock slides from the changing gravitational forces. Not to mention the tsunamis from the oceans sloshing around like water in a giant bath, as well as all the rockslides both above and below water. It would be a mess. Assuming this object would be travelling at 100km/sec, and the gravity would maybe begin to badly affect us when it was 50,000 km out from the surface of the earth (?) then it would take about 16 hours to travel from this distance, impact the earth and then reach this distance out the other side. I'm not sure how much energy would be released by the matter being consumed by the black hole - It might not be very much, after all its total gravitational pull wouldn't be very high, but would be travelling at probably at least 50+ km/second - certainly more than 11km/sec (earth escape velocity) The matter in front of the black hole might simply be swallowed up without much fuss, or if there is any "resistance" to this matter falling down past the event horizon I'd imagine it would be like a continuous series of nuclear bombs going off as matter was flash heated to the point of spontaneous nuclear fusion before it passed the event horizon. The one good point to note in all of this is it would be extraordinarily difficult to disturb this object from its object so it fell into the inner solar system. After all, it has the same mass as earth, and we don't have to be worried about random stuff disturbing earth's orbit.

debatem1 7y ago
This would be an extraordinary sci-fi story and I would pay good money to read it.
- kyralis 7y ago
  Not quite the same thing, but you might be interested in _The Forge of God_ by Greg Bear.
  - KiwiJohnno 7y ago
    I second that. Great book. The sequel, anvil of stars is pretty good too, but its a different setting
- sliken 7y ago
  Same here, maybe even write a simulation or two to help pin down some of the side effects. I did do a super simple simulation trying to explore if you could escape from beyond the event horizon where time dilation becomes so extreme that even very rare events become common. One of those extremely rare events could be when a galaxy collides with a second galaxy and the black holes at the center end up merging. Turns out you could escape from falling into a particular black hole if you had a second black hole to counteract the gravity. Unfortunately even while you are at zero acceleration, you end up inside an even larger event horizon formed by the two black holes. Your choices would be to fall into the first black hole, fall into the second, or wait for them to collide. Even the waiting isn't a particularly good option. While being outside the event horizon of a very large black hole minimizes the spagetification problem, there's no such protection inside the event horizon. In any case if interested in reading sci-fi based on black holes check out https://en.wikipedia.org/wiki/Black_holes_in_fiction https://en.wikipedia.org/wiki/Black_holes_in_fiction
- kevin_thibedeau 7y ago
  David Brin's Earth deals with a black hole stuck orbiting inside the planet. Also predicted Google glass backlash.
7y ago

intarga 7y ago

The point stands, it's not any more dangerous than an earth sized object of the same mass, in fact it's less. It isn't any easier to divert from it's orbit, it is not any more likely to collide with the earth if diverted (in fact less so on account of its small size), and it would be no more destructive on collision.

sliken 7y ago
If you drop the earth into the sun, the sun won't care. If you drop a black hole into the sun, the sun dies. Seems a wee bit more dangerous to me.

lumberingjack 7y ago

I read this book once.