Astronomy / Space The Big Black Bang Hole that wasn't

[Aquamonkey]

huh? That makes no sense to me, do you have a reference to support for your assertion? Just to be clear are you refering to the "big bang" and the expansion of space?

It has to do with the inverse square law. Every gravity well has an escape velocity whereby the object will forever experience the force of gravity pulling it back (asymptotically to zero with increasing distance), but it won't ever return. I.E. if the universe had a large enough initial velocity from the big bang such that it exceeded escape velocity, even with a zero vacuum energy, gravity wouldn't be enough to pull the universe back together.

 

[greenlantern]

It has to do with the inverse square law. Every gravity well has an escape velocity whereby the object will forever experience the force of gravity pulling it back (asymptotically to zero with increasing distance), but it won't ever return. I.E. if the universe had a large enough initial velocity from the big bang such that it exceeded escape velocity, even with a zero vacuum energy, gravity wouldn't be enough to pull the universe back together.

omg you have to be joking

 

[Aquamonkey]

omg you have to be joking

Escape velocity. Look it up.

 

[edd]

What doesn't sound right to you? the fact that the cosmological constant has a direct relation to the total mass in the Universe, it's basic cosmological theory. I suggest you check newtons laws of motion as a starting point, most 13 years old grasp its concepts fairly quickly.

I have a PhD in cosmology and the amount of cosmological constant isn't related to the amount of matter as far as we know. They are free parameters.

"No, it is only the case that it needs to be for an accelerating universe, which is not the same as ever expanding."

The vaccum energy density must be positive for an an ever expanding OR accelerating universe, so your correction was incorrect there again.

Classic low density open universes have no cosmological constant and expand forever.

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omg you have to be joking

It's not quite right to talk about escape velocities and the inverse square law here, but it happens that trying to do cosmology with Newtonian gravity can give the right answer. And it is a good analogy at the very least. If the initial expansion rate is high enough compared to the matter density it won't pull back together.

 

[Cargobane]

It might be hard to find, but a couple points back in here, edd and I actually agreed on some things. Maybe there is hope.. For him or me..