# Black holes with nothing left to ingest.

Nibles
If a black hole sucks everything into it that is near it, but at the same time has an event horizon, then everything between the event horizon and the black hole will get sucked it, but then there would be nothing else to suck in once it's all gone, unless the event horizon expands. Is this correct, or is it not? Thoughts?

Staff Emeritus
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1) All black holes have event horizons.

2) A black hole can certainly "suck everything in" around it. The problem you might be having is in your phrase "suck things in." Black holes don't really do that! Black holes exert gravitational forces on bodies near them, exactly as the Earth does to you, only stronger. You can orbit a black hole in your starship just as you can orbit the Earth in a space shuttle. Black holes act gravitationally just like any other massive body.

3) As a black hole captures matter and grows more massive, its event horizon expands. The radius of the event horizon is given by:

$$r_s = \frac{2 G M}{c^2}$$

- Warren

Staff Emeritus
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Welcome to Physics Forums, Nibles!

The event horizon is simply the distance around the black hole singularity at which nothing can escape. The black hole singularity and event horizon exist whether or not the black hole is actively consuming nearby material. Some current black holes are active (consuming stuff) others are not...just adrift in space orbiting the galactic center like any other star. Of course, they can become active again if something crosses their path.

chemical
black holes are weird We can't prove anything about the black holes, because they just don't work with our physics. once u enter a black hole, the speed of light will be different, etc. We can only assume that there is an event horizon, because we have no proof (apart from very distant photos) that the horizon is there or doesn't exist

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Originally posted by chemical
We can't prove anything about the black holes, because they just don't work with our physics.

The physics work just fine at a good distance from the singularity. The closer to the singularity, the weirder the physics. The singularity itself cannot be accurately described by modern physics.

We can only assume that there is an event horizon, because we have no proof (apart from very distant photos) that the horizon is there or doesn't exist

Based on the math, it should exist. (the EH is not a physical thing...it's merely a distance from the singularity)

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