Kind of an odd thing to wonder about I guess, but if you had a little black hole sitting in front of you, (and it wasn't sucking you in because that's no fun at all) could you exert any force on it? If you throw something at the hole, or as the title suggests, poke it with a stick, will it absorb Kinetic energy and begin to accelerate towards whatever direction the thing you hit the hole with was travelling? :-?

Well, if it didn't have any gravitational effect on you it really wouldn't be much of a blackhole. I guess, that if you could somehow turn off gravity for a while and get in close to a blackhole, you really wouldn't be able to see it, since a blackhole's singularity is a point particle.

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"Most editorials are written by people that love to argue but got kicked off debate team for not making any sense." -Seanbaby

Your question seems to be "Is it possible to exert a force on a BH?" I would think not but maybe some one else of greater knowledge can speak to that.

To address the other aspect of your question: With a very small black hole, one with mass small enough to create an event horizon a few centemeters in diameter, you could, concievably, be within a few feet and not be sucked in. The point of no return with a BH is the event horizon, where the escape velocity excedes 'C'. as long as you're safely distant from the event horizon you could use a broom stick or fishing pole to try to push the BH. Whatever part of your pole passes the EH will be gone forever. No warrenty, no return.

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A black hole is a mass just like anything else. If there were some way to exert a force on it, it would move. For example, a black hole will orbit the center of the Galaxy, due to the Milky Way's gravity. A BH in binary system orbits the other star.

Also, you could dump lots of electrons into one. It will gain a negative charge, and you could tow it around with an electromagnet. Really.

BA writes
Larry Niven used this trick in his story 'The Borderland of Sol'.

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I was just thinking of that Mike. I dreamt upon a Quark BH.. -Colt

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I just became curious as to another question.

Is there a minimum or maximum size for black holes?

Can we make a little one in 'the lab'?

Would a 'granddaddy' take out the universe?

I think I will post this in the "Black Hole FAQ" sticky thread as well.

http://www.badastronomy.com/phpBB/vi...=139757#139757

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Towing an electrostatically charged body around with an electromagnet? I don't think the magnet is significant. The chared body will attract any uncharged body, magnetic or not.

I beg to differ.

Magnets attract electrons to their south pole and protons to their north (or is it the other way?)
I remember learning it in school during motor dynamics. I no longer have the books to prove it, but I am sure I am not far off the mark.

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'Sir........, I don't like these numbers.'
'Then hire somebody that can change them!'
("`-/")_.-'"``-.,,
\. . `; -._( );, `)
(v_,)' _ )`-. \ ``'`
_.- _..-/ /((.'
((,.-' ((,/

Are you talking about the Lorentz force on moving electrons in a magnetic field? But in our case, I don't consider the electrons moving.

I guess I should have stated positive and negative charges, as opposed to electrons and protons.

A magnet doesn't care where the charge comes from, but it still either attracts or repels it.

That may be why it is the strongest large force in the universe.

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'Sir........, I don't like these numbers.'
'Then hire somebody that can change them!'
("`-/")_.-'"``-.,,
\. . `; -._( );, `)
(v_,)' _ )`-. \ ``'`
_.- _..-/ /((.'
((,.-' ((,/

Apologies to the real astronomers among you, but perhaps I could just answer Pinemartin:
(by all means correct me where I am wrong)
Is there a minimum or maximum size for black holes?
Can we make a little one in 'the lab'?
Would a 'granddaddy' take out the universe?

A tiny black hole would evaporate in a fraction of a second; any mass it contained would be liberated in the form of energy.
The smallest size possible would be a black hole 1 planck length in diameter (all diameters are across the event horizon; the singularity is assumed to be a dimensionless point).

if you have a slightly larger one it will still be evaporating, but it will be much smaller than an atom, and the energy coming out would push infalling matter away, so nothing could get in anyway.
A 1000 tonne black hole would last ~200 seconds, give off 1000 tonnes worth of pure energy, be smaller than a proton and look like a billion H-bombs going off.
As Black holes get bigger, the evaporation gets slower, untill you have one the mass of a medium sized asteroid, which is sucking stuff in as fast as it is irradiating energy.
This is about the size of a golf ball.

None of the above black holes have ever been seen, but it is possible the smallest ones may be manufactured one day, but these smallest ones will last just a tiny fraction of a second.

Bigger than that, they are stable, and actually start to increase in size as they suck more mass and energy in from ordinary space;

most of the black holes we know about are
EITHER formed from collapsing stars, and are about 3x as massive as the Sun (or more),
but only ten miles or so across the event horizon;
there are several objects in the sky which can best be explained as being black holes of this size;

OR formed in the early universe; each one weighs millions or billions of times the mass of the sun, and is perhaps fifteen million kilometers across- the diameter of a large star.

You could fly into a galactic black hole and hardly notice you had crossed the event horizon; but you would never get out again.

The maximum size for a black hole would have to be one which contains all the matter in the universe; thanks to the acceleration of the expansion of our universe I would have to say no, it could never happen.
But who knows?

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