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Author Topic: Do neutrons in a neutron stars bend Heisenberg's Uncertainty Principle?  (Read 20651 times)

Offline DoctorBeaver

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Measurement blah blah position harumph velocity mumble mumble; we all know the score by now.

So, in a neutron star there are all these neutrons (hardly surprising really). They're squeezed together very tightly by gravity; even tighter than Graham Norton and his "friend" at a Village People concert. Now if they're being squeezed together like that, surely it must restrict their movement somewhat. But do they have less freedom of position and velocity than ordinary neutrons at the centre of an atom? Could there come a point where their movement is so restricted by being squeezed together that the Uncertainty Principle either no longer applies or, at least, needs modifying?


 

Offline Alan McDougall

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Doc,

I don't think so, what about the black hole evil the sister of neutron stars. Some physicist postulate black holes could burp out nearly anything any possibility even multiple other Doctor Beavers in fact

I am interested, however, how entropy would work in energy flow in a neutron star

Alan
 

Offline JP

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I don't think so either.  The uncertainty principle says that the product of your uncertainties in position and momentum should be a constant:

However, that constant is incredibly tiny, so even in a densely packed neutron star, there is enough uncertainty about the positions and momenta of the particles so that the uncertainty principle is satisfied. 

If you collapse further into a black hole, then you could run into issues, since you're dealing with powerful gravitational effects on a quantum scale, and there's no generally accepted theory of how gravity will work on that scale yet.
 

Offline lightarrow

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Measurement blah blah position harumph velocity mumble mumble; we all know the score by now.

So, in a neutron star there are all these neutrons (hardly surprising really). They're squeezed together very tightly by gravity; even tighter than Graham Norton and his "friend" at a Village People concert. Now if they're being squeezed together like that, surely it must restrict their movement somewhat. But do they have less freedom of position and velocity than ordinary neutrons at the centre of an atom? Could there come a point where their movement is so restricted by being squeezed together that the Uncertainty Principle either no longer applies or, at least, needs modifying?
Probably about this there is no much difference from a neutron star and a nucleus; a neutron star's dimensions increase with the number of neutrons.
 

Offline DoctorBeaver

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I know Pauli's Exclusion Principle stops the neutrons being in the same quantum state; but they could never be squeezed together enough to be actually touching?
 

lyner

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Neutrons are bosons so Pauli doesn't apply to them. Nicht War?
 

Offline DoctorBeaver

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Not that I like feeling smug, you understand...

From Wikipedia:-

Neutron stars are very hot and are supported against further collapse because of the Pauli exclusion principle. This principle requires that no two neutrons can occupy the same quantum state simultaneously.

From http://www.physics.org/explore-results-all.asp?hsub=1&q=pauli:-

Neutron degeneracy is a stellar application of the Pauli Exclusion Principle, as is electron degeneracy. No two neutrons can occupy identical states, even under the pressure of a collapsing star of several solar masses.

 [^]
 

Offline lightarrow

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Neutrons are bosons so Pauli doesn't apply to them. Nicht War?
Neutrons are fermions, not bosons:
http://en.wikipedia.org/wiki/Fermion
 

Offline DoctorBeaver

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Neutrons are bosons so Pauli doesn't apply to them. Nicht War?
Neutrons are fermions, not bosons:
http://en.wikipedia.org/wiki/Fermion

Oh yeah, I forgot to add that bit.
 

lyner

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Owch!
What can I have been thinking of?
 

Offline DoctorBeaver

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Owch!
What can I have been thinking of?

Christina Aguilera?
 

lyner

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I'd go for that.
 

Offline DoctorBeaver

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Anyway, so Pauli supports Heisenberg. But it is possible that under extreme conditions like those in a neutron star (where densities can reach 5.9 1017 kg/m) the difference in quantum states can be almost infinitely small?
 

Offline Alan McDougall

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DoctorBeaver,

With all repect to th great Pauli, how do we know his exclusion principle is fact?

Alan

 

 

Offline DoctorBeaver

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DoctorBeaver,

With all repect to th great Pauli, how do we know his exclusion principle is fact?

Alan


Because we can't walk through walls?  :P
 

Offline Alan McDougall

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Doctor Beaver,

Quote
Because we can't walk through walls?

Are you sure?  ;)

A man made of neutrinos could  ;D

Alan

   
 

lyner

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Anyway, so Pauli supports Heisenberg. But it is possible that under extreme conditions like those in a neutron star (where densities can reach 5.9 1017 kg/m) the difference in quantum states can be almost infinitely small?
You don't have to go to a neutron star to get into the realm of energy bands. Solid state physics works with them all the time - i.e. assuming a continuum of states.
The Hydrogen Atom is not always a lot of help with working out the situation in anything other than a gas. And the Hydrogen atom is the most often quoted or implied in this sort of topic.
 

Offline DoctorBeaver

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Anyway, so Pauli supports Heisenberg. But it is possible that under extreme conditions like those in a neutron star (where densities can reach 5.9 1017 kg/m) the difference in quantum states can be almost infinitely small?
You don't have to go to a neutron star to get into the realm of energy bands. Solid state physics works with them all the time - i.e. assuming a continuum of states.
The Hydrogen Atom is not always a lot of help with working out the situation in anything other than a gas. And the Hydrogen atom is the most often quoted or implied in this sort of topic.

Who mentioned hydrogen?
 

lyner

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You, dear boy,  were implying that sort of model because you suggested that there is something special about the close spacing of energy levels in a neutron star. I was simply pointing out that it happens in all condensed matter (though, of course, not as close).
 

Offline DoctorBeaver

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But it's the extreme closeness I'm talking about. You don't get neutrons pressed together in hydrogen of any type.
 

lyner

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But what about the fact that ordinary condensed matter behaves that way too? (i.e. a band structure)
You seem to be implying something special about neutrons in neutron stars when it's just a matter of degree.
 

Offline DoctorBeaver

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But it doesn't because in ordinary condensed matter there are electron energy levels to take into account. Neutrons in a neutron star don't have them.

Think of it this way. Take 20 marbles and put them in a large box. Shake the box and the marbles can move. However, if you pack them into a smaller box, their movement is restricted. Put them in a box just big enough to take them and they can't move at all. That's the situation I was asking about; can the density in a neutron star be great enough to press the neutrons so hard together that they can't move?
 

lyner

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'Neutrons as marbles' is too naive, as a model, I think.
With a box, 'jam packed' with marbles, you can go one step further and squash the marbles out of shape and they will take up even less room.
With a solid, you can compress it with enough energy (albeit, a lot) and the energy would involve electron energy states. But they're not really 'electron states' - the states describe to the whole atomic system.
With enough Energy, why can you not expect to distort the neutrons also?  After all, a neutron is a proton plus an electron (or you can go deeper if you want),  and the energy state involves some different mechanics.
 

Offline DoctorBeaver

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That's exactly what I'm getting at, though. You can compress & compress until you get to the quarks. You can't compress quarks as they're fundamental.

You see, this is 1 of the things I don't get about Heisenberg's principle. If you could stop the neutrons moving by squeezing them tightly enough together the quarks would still have as much freedom of movement as ever. But you could know both the positions (stationary) and momenta (zero) of the neutrons. So where does HUC stop? At fundamental particles or with composite particles?

I only used the marbles as a very simplistic analogy.
 

Offline JP

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How do you propose to measure the position or velocity of a neutron, considering its made up of quarks?  You'd probably have to somehow measure some property of the quarks.  Therefore, if all the quarks obey the uncertainty principle, shouldn't the neutron position necessarily obey the uncertainty principle?
 

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