gravitational force

[triclino]

What is the biggest gravitational force in the Universe??

[beefpatty]

By "biggest" do you mean strongest, or size-wise biggest? The biggest known gravitationally-bound structure in the universe is a mind-boggling 4 billion light years across!

 

In terms of strength, though, black holes are probably the "strongest", simply because you can get very, very, very close to their center of gravity.

[triclino]

The strongest recorded

[elfmotat]

I'm not really sure what you mean by "strongest." The "g" value (which on Earth is ~9.8 m/s²) approaches infinity near the event horizon of any black hole.

[Elite Engineer]

If by strongest "gravitational pull", it would be a blackhole(s), which has infinite mass, and gravitional pull so strong, not even photons can escape their gravitional force.

[elfmotat]

If by strongest "gravitational pull", it would be a blackhole(s), which has infinite mass, and gravitional pull so strong, not even photons can escape their gravitional force.

 

Black holes don't have infinite mass. Infinite mass would imply infinite Schwarzschild radius, so the entire universe would be swallowed up.

[Dekan]

Might the biggest force be neutrons? They have no electric charge. Yet they make protons stick to them in atoms. Could this be because the protons get pulled by the gravity of the neutrons. If so, neutrons might be the real cause of gravity.

 

That would explain why gravity doesn't seem to affect Hydrogen gas very much. It's because pure Hydrogen molecules don't contain neutrons. So Hydrogen is not susceptible to gravity - it floats about freely throughout the Universe.

[MigL]

Oh, come on !!

 

A little thinking before posting goes a long way.

[pwagen]

So Hydrogen is not susceptible to gravity - it floats about freely throughout the Universe.

Except for the times when the hydrogen pulls together to form a cloud due to gravity.

[Dekan]

Yes, but can Hydrogen really pull itself together? A pure Hydrogen atom only has 2 particles in it:

central Proton, and outer Electron. Both particles always stay the same distance apart.

They are, so to speak, satisfied. They don't push or pull each other, but relax together in equilibrium. No gravity, just peaceful co-existence. The pure Hydrogen atom always stays the same size. So shouldn't a cloud of such atoms, also stay the same size?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[pwagen]

The pure Hydrogen atom always stays the same size. So shouldn't a cloud of such atoms, also stay the same size?

No, a single atom and a cloud of atoms behave very differently. Gravity, for example, would have an effect on the cloud, but virtually none on the single atom, while the strong force would be undetectable in the cloud, but have a huge effect inside the atom.

[MigL]

So how do you assume stars form Dekan ?????

 

And for that matter, given sufficient gravity, the electrons of an atom, even hydrogen, are forced into the nucleus ( or proton ) to form neutronium. Or how do you assume neutron stars form ???

 

And have you never heard of the strong nuclear force ???

Edited April 16, 2013 by MigL

[Enthalpy]

...A Hydrogen atom has a Proton and an Electron [that] stay the same distance apart... They don't push or pull each other, but relax together in equilibrium. [...] So shouldn't a cloud of such atoms, also stay the same size?

 

It's all a matter of size. The proton and electron attract an other very strongly, but because they're waves, they can't become arbitrarily small, since a too small wave would have increasingly more kinetic energy, to the point where this increase is worse than the benefit from the particles of opposite charge being closer to an other. This is what defines the atom's volume: so to say, the nucleus and electron(s) have already collapsed together, down to the most favourable size.

 

Bigger objects like a gas cloud don't have this minimum volume resulting from their wavelength, because a wavelength the size of the cloud would mean a negligible kinetic energy. So this reason does not prevent the collapse of a cloud. Other reasons can prevent or brake the collapse, especially the central pressure; the usual theory tells that some heat radiation mechanism must allow the cloud to cool down, hence reduce its central pressure, to go on contracting despite this contraction heats it.

 

[Maybe someone will model that nuclides must be distinguished in that process, and that heavier ones can coalesce by expelling lighter ones. Or maybe I'm horribly wrong. No established science now, in any case.]

 

Under extreme density resulting from gravitation, the weak force can make neutrons out of protons and electrons; the necessary conditions differ a lot from a contracting gas cloud.

[Przemyslaw.Gruchala]

Under extreme density resulting from gravitation, the weak force can make neutrons out of protons and electrons; the necessary conditions differ a lot from a contracting gas cloud.

 

Electron capture happens in different situations.

 

Typical fusion in stars:

 

p+ + p+ -> D+ + e+ + Ve

D+ + p+ -> T+ + e+ + Ve

T+ -> He + e- + Ve

D+ + D+ -> He

e+ + e- -> y+y

Edited April 20, 2013 by Przemyslaw.Gruchala

[Dekan]

The above posts are very valuable. They seem to show that in order to explain "Gravity", we must get back to the neutron - which is not a positive particle, like the proton, nor a negative particle, like the electron.

 

The neutron is halfway between them. It joins two opposites together. A binding force, if you will.

 

Consider: suppose the Universe contained only protons. They'd all fly apart from each, repelled by their mutual positive charge. And, if the Universe contained only electrons, they'd do the same, repelled by their mutual negative charge. In either case - you'd never get "Gravity", which allows protons and electrons to cohere into atoms, and so make planets and stars.

 

So "Gravity" must be caused by a third particle. Is it the neutron?

Edited April 20, 2013 by Dekan

[swansont]

Yes, but can Hydrogen really pull itself together? A pure Hydrogen atom only has 2 particles in it: central Proton, and outer Electron. Both particles always stay the same distance apart. They are, so to speak, satisfied. They don't push or pull each other, but relax together in equilibrium. No gravity, just peaceful co-existence. The pure Hydrogen atom always stays the same size. So shouldn't a cloud of such atoms, also stay the same size?

 

Hydrogen pulls itself together to form stars. The gravity of one hydrogen atom is negligible compared to the electromagnetic interaction that holds it together, but that atom is neutral, so that same force does not continue to propagate. Gravity, though, does not experience shielding, so it continues to grow as the mass grows.

 

The above posts are very valuable. They seem to show that in order to explain "Gravity", we must get back to the neutron - which is not a positive particle, like the proton, nor a negative particle, like the electron.

 

The neutron is halfway between them. It joins two opposites together. A binding force, if you will.

 

That's sort of true, inside the nucleus. But not for gravity. Gravity is not responsible for forming individual atoms or molecules.

 

 

 

Consider: suppose the Universe contained only protons. They'd all fly apart from each, repelled by their mutual positive charge. And, if the Universe contained only electrons, they'd do the same, repelled by their mutual negative charge. In either case - you'd never get "Gravity", which allows protons and electrons to cohere into atoms, and so make planets and stars.

 

So "Gravity" must be caused by a third particle. Is it the neutron?

 

No, gravity depends on total mass. Not just the neutrons.

[howlingmadpanda]

It would be black holes, the reason earth has gravity is because (In theory of relativity) its large mass warps time and space, a black hole has such a strong force because when this huge star collapses that much matter into such a small area, ALOT of pull would be generated.