Black Holes are Misunderstood
The scary bit about a black hole is that you can’t see it,
because it’s hiding behind its “event horizon”; the invisible sphere,
surrounding the black hole, from which light cannot escape. So you could
accidentally stray into its gravitational field without knowing it’s there,
until you suddenly feel yourself being strongly pulled towards it!
The radius of the event horizon (on formation) is very much less
than the radius of the star that collapsed to form it. While the radius of the
Sun is 7 x 108 m, that of a Schwarzschild black hole of 10 solar
masses is only 3 x
104m. It’s only when you get closer to the black
hole than the radius of the original star, that the weird stuff happens.
Distant objects are no more strongly pulled towards a black
hole than towards a star of the same mass.
When a star collapses to form a black hole, it loses mass
due to the energy squeezed out, according to Einstein’s mass/energy
relationship. (E=mc2).
The minimum mass required of a star to become a black hole
is about 6 solar masses. Less than that, it becomes a neutron star, and if much
less it becomes a white dwarf.
We could not create a black hole accidentally on Earth
because there is nowhere near enough mass in our neighbourhood to be able to do
so. The Sun contributes 99% of the mass of the solar system, and the nearest
massive objects, outside the solar system, are in the constellation Centaurus, 5 light years away.
Maybe some of the Centaurus constellation stars, at that distance, could potentially merge at some time in the distant future, and become a black hole, but at that distance would exert no bigger gravitational pull, on us, than they do now.
You can all calm down now.
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