Brigade XO wrote:So....what is the smallest a Black Hole can be? Or, to ask it differently, how large does a mass have to be to initiate the effect of gravity caused by said mass to collapse the matter involved into a Black Hole and what would be the diameter of said hole?
As tlb answered, any mass can be a black hole, so long as all of it is contained within the Schwarzschild radius of that mass.
So your question is just how one can put that much mass inside that tiny radius. The discussion above was about using energy density and E=mc² to do that, but we currently don't have technology to create such a BH.
The other way is that those were created during a very early age of the Universe, when the density was almost uniformly sufficient. Because it was uniform, it didn't collapse everywhere into a BH. But tiny variations in density could have created tiny BHs that would survive until this day: primordial black holes. This theory is sound, but no such PBH has ever been observed. In fact, we've been able to rule out many mass ranges for them, because if they had been there, we'd have seen them.
Finally, there's the traditional way of creating a BH: just too much mass packed together. The minimum mass for that is wel-known (if not precise): the
Tolman–Oppenheimer–Volkoff limit. The current best estimates are of right about 3.0 solar masses.
Does the formation of a Black Hole create a giant sucking effect in every direction like turning on a star sized vaccume cleaner?
No. If the Sun were replaced by a BH of the same mass (see above how creating such would be difficult), we'd all die, but only because we suddenly lost our best source of energy. But if we had a way to generate energy ourselves and still feed ourselves, we could live on. The orbit of all the planets and asteroids would be undisturbed.
A BH of a given mass has the exact same gravitational attraction as any other body of the same mass, at the same distance. The difference is that a BH is so small that you can get far, far closer to it, than any other body. And close by it, things get really freaky, like frame dragging: a rotating BH can drag spacetime outside the event horizon.
And why, pray tell, have various story universes use "singularities" as their power sources? I thought that was another term for Black Hole (at least in popular usage) and how would it power anything since what it does is pull EVERYTHING into itself- how do you get "power" out of it unless you have an equivalent of a turbine being spun by the movement of matter/light/whatever from the outside to the event horizon.
Not accepting "artistic license" as an explination. Big Smile
A BH is expected to produce energy, called the Hawking Radiation. That is nowadays accepted as fact, even though we have yet to measure it in any known BH. The power it produces is inversely proportional to the square of its mass, so the larger the BH is, the less it produces of power. The smallest known BH, at 3.04 solar masses, would be producing power in the 10^(-29) W range. There's no way we could see any effect of that.
However, if you make them smaller, much smaller, then you can extract useful energy from them, within practical time periods. The sweet spot would be in the range of one billion tonnes: such a BH would produce 356 MW of power and would last for 1.4 trillion years before it evaporated completely. And you can keep it alive indefinitely if you feed it mass.
All of this is within our known bounds of Physics.
Sci-Fi usually takes this much further. Most singularity drives aren't simple power generators. Singularity drives (often Artificial Quantum Singularities, AQS) usually exhibit properties that our physics don't account for, including the ability to somehow go FTL, travel between universes or dimensions, etc.