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Heliocentrism and geocentrism

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The VLT Survey Telescope at ESOs Paranal Observatory in Chile has captured this richly detailed new image of the Lagoon Nebula

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Question: If 2 black holes get near each other, can they then gravitationally pull matter out of the other black hole & back into “normal” space?

The short answer is no.

A black hole (in the traditional sense) is defined as an object that has collapsed so that its radius is equal to, or less than, the Schwarzschild of the object.

What does this mean?

Every object has a Schwarzschild radius; this is the point at which an object’s mass is so compressed that the gravitational influence overpowers the other forces of nature and it collapses to a singularity.

Of course, not every object is massive enough to collapse to its Schwarzschild radius. The Earth’s Schwarzschild radius, for example, is about the diameter of a small marble. If you were to apply enough energy to the Earth and compress its mass to that size, it would collapse to form a black hole. The same is true for humans, except I’d need to compress you to a point some 10-million times smaller than a marble in order to turn you into a black hole.

So, what is special about the Schwarzschild radius? This is the point at which the escape velocity for the object is equal to the speed of light. Obviously, since you can’t travel ,or faster than, the speed of light you can’t get out of a black hole neither can another black hole pull you out.

It’s important to realize that, outside of the Schwarzschild radius (also known as the event horizon), spacetime is normal. You can interact with a black hole in the same ways you interact with any other object of mass.

Image credit: NASA/CXC/A.Hobart

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Hedyphane

Varying from white to yellowish with occasional reddish or green specimens, it was named after its discovery in Sweden in 1830 from the Greek words for ‘appearing beautiful’. It is a rare critter, only forming in manganese or zinc ore deposits that have been metamorphosed by heat and pressure deep within the crust, or when intruding granites bake the surrounding rock. It is a part of the apatite group (see http://bit.ly/2akYWkg)and includes lead and calcium combined with arsenic and oxygen in its composition, being an analogue of another pretty mineral called mimetite (see http://on.fb.me/1zo1vvI).

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Moments after this photo was taken, Sean and Michael McQuilken were struck by lightning.  Both boys survived.