Thread: Is gravity always attractive?

I have read that gravity is always attractive.

However, frame dragging, or the gravitational effects of spinning matter, is used to explain jets of energy/particles that shoot out of spinning black holes and quasars.

If gravity is always attractive, then why do these jets shoot out from the black hole?

It seems that the spin of the black hole is negating the black hole's massive gravity, and allowing the jets to escape.

Can anyone explain this?

Thanks,

Dedo

Very interesting question. I hope someone knows more about this.


My best guess is that it has to do with the black hole's momentum. Gravity is always attractive, but it there's also something called the "slingshot" effect, where an object can pull on you with its gravity, and then move out of the way before you hit it, thereby catapulting you past it.

This effect is used by NASA to send satellites into the outer reaches of the solar system. They send the satellites initially inward toward Mercury and Venus at just the right trajectory so the planets will slingshot them outward toward Saturn, Jupiter, Neptune, and etc.

Originally Posted by dedo

I have read that gravity is always attractive.

However, frame dragging, or the gravitational effects of spinning matter, is used to explain jets of energy/particles that shoot out of spinning black holes and quasars.

If gravity is always attractive, then why do these jets shoot out from the black hole?

maybe the mass is exceeeding the speed of light and that is why it escapes?

or perhaps the hole ideology is a weeeeeee bit off. (i like your point, keep the tinker tinking)

It seems that the spin of the black hole is negating the black hole's massive gravity, and allowing the jets to escape.

Can anyone explain this?

Thanks,

Dedo

well we know it aint centripedal nor centrifical (ie... hubble observance of the mass in the arms, is moving too fast (see 'mass curve' (Keplerian))

or just read the physics
http://astro.physics.uiowa.edu/~rlm/...k%20matter.htm


ie....... the physics behind your question and in reality the hole ideology uses not a one of the funny forces often found in classroom across the hall

for example; one minute NOTHING can escape the event horizon (not even light) the next a black hole is going poopy and spitting out vast amounts.........


hence your question; "is gravity always attractive?"

[quote="Bishadi"]

Originally Posted by dedo

for example; one minute NOTHING can escape the event horizon (not even light) the next a black hole is going poopy and spitting out vast amounts.........


hence your question; "is gravity always attractive?"

Wrong, as usual.

The jets that appear to come from a black hole are due to the acretion disc, Nothing is coming from the other side of the event horizon.

some point:

First off frame dragging is only one of two possible mechanisms posited to explain relativistic jets. The other involves magnetic fields.

Nothing leaves the event horizon. The jets are formed from material falling in from the accretion disc and redirected outward before it reaches the event horizon.

Both mechanisms get the required energy to form these jets from the rotation of the Black hole. The particles gain energy at the expense of the black hole's rate of rotation.

Originally Posted by kojax

Very interesting question. I hope someone knows more about this.


My best guess is that it has to do with the black hole's momentum. Gravity is always attractive, but it there's also something called the "slingshot" effect, where an object can pull on you with its gravity, and then move out of the way before you hit it, thereby catapulting you past it.

This effect is used by NASA to send satellites into the outer reaches of the solar system. They send the satellites initially inward toward Mercury and Venus at just the right trajectory so the planets will slingshot them outward toward Saturn, Jupiter, Neptune, and etc.

O.K., so nothing can get past the event horizon.

So if gravity is always attractive, how could Frame dragging pull material from the accretion disk to make relativistic jets moving away from the black hole?
Is frame dragging ever repulsive?

Or could there be some sort of "sling shot" created by the spinning black hole or its associated magnetic fields?

Originally Posted by dedo

Originally Posted by kojax

Very interesting question. I hope someone knows more about this.


My best guess is that it has to do with the black hole's momentum. Gravity is always attractive, but it there's also something called the "slingshot" effect, where an object can pull on you with its gravity, and then move out of the way before you hit it, thereby catapulting you past it.

This effect is used by NASA to send satellites into the outer reaches of the solar system. They send the satellites initially inward toward Mercury and Venus at just the right trajectory so the planets will slingshot them outward toward Saturn, Jupiter, Neptune, and etc.

O.K., so nothing can get past the event horizon.

So if gravity is always attractive, how could Frame dragging pull material from the accretion disk to make relativistic jets moving away from the black hole?
Is frame dragging ever repulsive?

Or could there be some sort of "sling shot" created by the spinning black hole or its associated magnetic fields?

The jet is composed of charged particles, so it is the magnetic field of the BH that redirects them. Where frame dragging would come in would be to transfer rotational energy of the BH to the particles so that they have enough velocity to escape the vicinity of the BH (rather than just falling back in).

Originally Posted by dedo

Originally Posted by kojax

Very interesting question. I hope someone knows more about this.


My best guess is that it has to do with the black hole's momentum. Gravity is always attractive, but it there's also something called the "slingshot" effect, where an object can pull on you with its gravity, and then move out of the way before you hit it, thereby catapulting you past it.

This effect is used by NASA to send satellites into the outer reaches of the solar system. They send the satellites initially inward toward Mercury and Venus at just the right trajectory so the planets will slingshot them outward toward Saturn, Jupiter, Neptune, and etc.

O.K., so nothing can get past the event horizon.

So if gravity is always attractive, how could Frame dragging pull material from the accretion disk to make relativistic jets moving away from the black hole?
Is frame dragging ever repulsive?

Or could there be some sort of "sling shot" created by the spinning black hole or its associated magnetic fields?

It's important to remember that a black hole's gravity extends outside the event horizon as well. The slingshot effect would only work if the whole event horizon moves out of the way before the particle reaches the event horizon. ... so I guess it's less likely, but certainly not impossible.

I wonder if it's possible for a black hole to gain an electrical charge greater than the magnitude of its gravity?

Originally Posted by Janus

Originally Posted by dedo

Originally Posted by kojax

Very interesting question. I hope someone knows more about this.


My best guess is that it has to do with the black hole's momentum. Gravity is always attractive, but it there's also something called the "slingshot" effect, where an object can pull on you with its gravity, and then move out of the way before you hit it, thereby catapulting you past it.

This effect is used by NASA to send satellites into the outer reaches of the solar system. They send the satellites initially inward toward Mercury and Venus at just the right trajectory so the planets will slingshot them outward toward Saturn, Jupiter, Neptune, and etc.

O.K., so nothing can get past the event horizon.

So if gravity is always attractive, how could Frame dragging pull material from the accretion disk to make relativistic jets moving away from the black hole?
Is frame dragging ever repulsive?

Or could there be some sort of "sling shot" created by the spinning black hole or its associated magnetic fields?

The jet is composed of charged particles, so it is the magnetic field of the BH that redirects them. Where frame dragging would come in would be to transfer rotational energy of the BH to the particles so that they have enough velocity to escape the vicinity of the BH (rather than just falling back in).

So you are saying that the effect of the rotating black hole is basically to accelerate the particles so the particles can escape.

O.K. I think I understand.

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yeah well i think it'l be great if we can switch on & off the gravity!!!!!

Yeah, but that's not the way it works in this Universe.

Feel free to make up one of your own, that has nothing to do with reality.

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Is gravity always attractive?
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[QUOTE=kojax;192331][quote=dedo]

Originally Posted by kojax

I wonder if it's possible for a black hole to gain an electrical charge greater than the magnitude of its gravity?

The electron beams that project along the rotational axis of the accretion disk would be aligned there due to a positive charge on the disk. Such orientation would account for their outward travel: mutual repulsion. Obviously, the black hole would have first grabs at these electrons, but it has limited appetite for them. Why? Because it already has had its fill of them. By that, I mean that it has swallowed so many electrons that its repulsion for an electron equals its attraction for one. However, after swallowing another bit of neutral matter, its electron appetite will have been restored and it can help itself to another electron due to having gained some weight.

Would it be disrespectful for us to suppose that under these circumstances, an electron might straggle either way along the rotational axis just short of the singularity? Such maneuvers would take exception to proclamations that nothing can escape the event horizon.