Whack degenerate matter with a baseball bat

[Toadie]

Hi all,

 

I'm a relative noob to physics, but yesterday a question came to mind:

 

If degenerate matter has maximum density, what would happen if you were to, say, whack it with a baseball bat? If F=ma and you apply a force to the degenerate matter, then it must produce some acceleration by the degenerate matter. My understanding would tell me that the entire mass would not accelerate uniformly, but it would deform to a degree; the matter closest to the impact would accelerate first, and after some period of time, however small, the rest of the mass would accelerate.

 

Obviously if this were the case, the problem would be that the degenerate matter is already at maximum density, but the deformity from the external force would change some local density to exceed the maximum.

 

So what would happen? Would the who mass indeed accelerate uniformly, or would something else happen?

 

 

I understand that this situation is quite outlandish but my curiosity has got the better of me.

 

Any input is greatly appreciated.

[Schrödinger's hat]

Awesome question.

For one, degenerate matter won't always be at its maximum density/all be degenerate matter.

So it might just act like very very very strong dense normal matter (your bat may not survive, depending on how you're containing this degenerate matter).

 

The other possibility is that it's at exactly its maximum density.

In this case two things might happen:

First, you'll force some portion of it to overcome degeneracy pressure.

So if it was electron degeneracy pressure it might become neutron degeneracy pressure,

Neutron degeneracy pressure would enter a state I don't know about. This would be the same process a neutron star undergoes in the relevant kind of supernova. Whether any amount of this matter would become a black hole, I don't know.

 

This new state could be stable, if -- say -- it was a sphere you were hitting. It'd be the straw that broke the camel's back, so to speak and the object would collapse into either a neutron star or a black hole (the resulting explosion would be unpleasant).

Or it might be unstable. If your degenerate matter were somehow magically a different shape you might change some of it into a black hole which will immediately explode due to hawking radiation.

In some weird circumstance (maybe your containment is really good, but not based on the objects self-gravity) it might just settle back into being degenerate matter again, I'm not quite sure.

[mathematic]

I would guess that if you somehow got a piece of degenerate matter on earth, it would quickly become undegenerate. I won't venture as to end product, but I suspect it would a massive block of ordinary matter.

[imatfaal]

I would guess that if you somehow got a piece of degenerate matter on earth, it would quickly become undegenerate. I won't venture as to end product, but I suspect it would a massive block of ordinary matter.

 

I don't think there is any reason for the degenerate matter to explode outwards - its gravity holds it together. there is probably a mechanism for it to expand slowly - bit one doesn't present itself to mind. I guess it would fall straight to centre of earth or damn close, a grapefruit sized lump would have a mass of ~10^14 kg and would be have an attraction to the centre of the earth of about ~10^15 N

[mathematic]

I don't think there is any reason for the degenerate matter to explode outwards - its gravity holds it together. there is probably a mechanism for it to expand slowly - bit one doesn't present itself to mind. I guess it would fall straight to centre of earth or damn close, a grapefruit sized lump would have a mass of ~10^14 kg and would be have an attraction to the centre of the earth of about ~10^15 N

If you got a small chunk (I'm guessing), gravity would be too weak to hold together against quantum mechanical forces.

[imatfaal]

If you got a small chunk (I'm guessing), gravity would be too weak to hold together against quantum mechanical forces.

 

Guessing as well - degenerate matter has already overcome those forces - the amount of mass in such a small volume is enough to do it, and I don't see what has changed

[Schrödinger's hat]

I think mathematic's point was that the phrase 'degenerate matter on earth' implies a much smaller quantity than the stellar-mass sized chunks we observe in nature. If it were a white dwarf or neutron star, the phrase would be 'earth in degenerate matter'.

 

Guessing as well - degenerate matter has already overcome those forces - the amount of mass in such a small volume is enough to do it, and I don't see what has changed

 

If we extend this logic to arbitrarily small chunks of neutron-degenerate matter, all nuclei are stable.

Thus there is a tipping point where (at least for neutron-degenerate matter) it is unstable.

Iit is impossible to know where this line is without modelling the relevant equations for a small amount of mass, Or doing some kind of experiment. However, I'd wager that it'd be closer to the mass of a planet than the mass of a mountain.

 

Similarly the logic of:

It is in this state, therefore it is stable.

Does not hold for electron degenerate matter.

[imatfaal]

I think mathematic's point was that the phrase 'degenerate matter on earth' implies a much smaller quantity than the stellar-mass sized chunks we observe in nature. If it were a white dwarf or neutron star, the phrase would be 'earth in degenerate matter'.

I understand Mathematics point - and instinctively I agree with both you and him. But when a collection of atoms reaches a certain density then you get electron degeneracy - then at a higher density you get neutron degeneracy (via proton degeneracy that no one bothers with), then quark degenerate matter... I do not see the path way for this to reverse

 

 

If we extend this logic to arbitrarily small chunks of neutron-degenerate matter, all nuclei are stable.

Thus there is a tipping point where (at least for neutron-degenerate matter) it is unstable.

Iit is impossible to know where this line is without modelling the relevant equations for a small amount of mass, Or doing some kind of experiment. However, I'd wager that it'd be closer to the mass of a planet than the mass of a mountain.

the move to nuclei is I think a bit of a red herring - as a spurious example free neutrons decay in about 15 mins 1/2life , so what are all these neutron stars doing staying around; different rules apply. And the density of an atomic nucleus is less than the average density of a neutron star. I understand your point - but not sure how it helps.

 

I am trying to get my head around the changing gravity with mass - but think I will have to revert to sums

 

Similarly the logic of:

It is in this state, therefore it is stable.

Does not hold for electron degenerate matter.

 

At what point does it stop holding? It holds for neutron stars - now a star under the chandrasekhar limit would not collapse to degeneracy under it's own mass, but we are not talking about the collapse process. degeneracy occurs because gravity overwhelms the other forces and exclusions - once it is in this state what occurs to reverse that process? It would seem that removing any bit of it would require great input of energy due to the steep gravitational potential

 

by the by - I have never read that micro-black holes are unstable - sure they burn off with hawking radiation very quickly- but they do not re-enlarge.

 

 

edit after rethought

 

1. gravitational attraction at the surface must vary linearly with the radius for constant density for simple states of matter - if this applies then there will be a level at which that can no longer hold against fermionic etc. I just cannot get my head around the pressure equations to make a stab at whether that is the case or at what point that will be.

Edited December 12, 2011 by imatfaal

[Schrödinger's hat]

I understand Mathematics point - and instinctively I agree with both you and him. But when a collection of atoms reaches a certain density then you get electron degeneracy - then at a higher density you get neutron degeneracy (via proton degeneracy that no one bothers with), then quark degenerate matter... I do not see the path way for this to reverse

 

 

 

the move to nuclei is I think a bit of a red herring - as a spurious example free neutrons decay in about 15 mins 1/2life , so what are all these neutron stars doing staying around; different rules apply. And the density of an atomic nucleus is less than the average density of a neutron star. I understand your point - but not sure how it helps.

 

I am trying to get my head around the changing gravity with mass - but think I will have to revert to sums

The difference is the deep (and steep) potential they are in. Change the gravity (by changing the totall amount) and you can't say that the previously stable state will stay stable. (Similarly I cannot say without doing the sums that it will be unstable, but I know there is a point somewhere between a neutron and a stellar mass ball of neutrons that it becomes unsstable)

 

 

At what point does it stop holding? It holds for neutron stars - now a star under the chandrasekhar limit would not collapse to degeneracy under it's own mass, but we are not talking about the collapse process. degeneracy occurs because gravity overwhelms the other forces and exclusions - once it is in this state what occurs to reverse that process? It would seem that removing any bit of it would require great input of energy due to the steep gravitational potential

 

by the by - I have never read that micro-black holes are unstable - sure they burn off with hawking radiation very quickly- but they do not re-enlarge.

I would call burning off quickly an unstable state, but regardless, when it comes to having an event horizon things are a bit different.

edit after rethought

 

1. gravitational attraction at the surface must vary linearly with the radius for constant density for simple states of matter - if this applies then there will be a level at which that can no longer hold against fermionic etc. I just cannot get my head around the pressure equations to make a stab at whether that is the case or at what point that will be.

 

I can't quite follow what you said in that last bit, but I think it may be the same line of logic I was using.