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How would neutron star matter behave on earth?

  1. Mar 29, 2011 #1
    Neutrons have no charge, and in neutron stars we have matter that is only made of tightly packed neutrons. The mass is very great due to density.

    If I were to go fetch a baseball sized ball of neutron star matter from a neutron star and lay it on hard concrete ground.....

    Other than making a dent in the ground because of it's massive weight what would happen?

    Would the neutrons expand violently or would there be chemical reactions with electrons and protons?
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  3. Mar 29, 2011 #2


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    It's the extreme gravity in the neutron star that keeps the matter compressed to extremely high densities. Once you removed the baseball sized clump of matter from the neutron star, the pressure of gravity would no longer be compressing it, and the matter would expand violently (i.e, explode). There is no way you could get it back to earth to try your experiment. You couldn't put it into some sort of "bottle" to keep it compressed, because no ordinary matter is strong enough to keep it compressed,
  4. Mar 29, 2011 #3
    Well i guess I will make a bomb out of it then....:=)
  5. Mar 29, 2011 #4
    phyzguy summed it up well...

    ...in a hypothetical world in which one could bring back a handful of neutron star matter and place it on the ground here on earth, it wouldn't matter how strong or dense the ground beneath the neutron star material is - it would never be as dense as the neutron star material itself. and so such an object would punch a hole in the ground and would not settle until it reached the center of the earth. i don't remember what the exact quantities are, but a spoonful of neutron star matter could weigh as much as a mountain on earth (hundreds of millions of tons). the reason a mountain doesn't punch a hole in the surface of the earth and sink to the center is b/c its weight is distributed over several, perhaps hundreds, of square miles. an object that weighs as much as a mountain, but whose weight is only distributed over several square inches, would sink to the center of the earth provided it can maintain its density here on earth (which, as phyzguy pointed out, is impossible here on earth).
  6. Mar 29, 2011 #5


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    Doubtful - there is no way you could get a chunk of it.
  7. Mar 29, 2011 #6

    Yes but just because something has more density than the ground doesn't mean that it's going to sink, it's called electromagnetic forces the solid matter doesn't let other matter trough itself easily just because it's heavier. If that was the case you couldn't but an iron pole on grass without it sinking to the bottom of the earth.

    But still I understand what you mean the neutron star would probably be way too heavy for the ground too support it.

    But I have another question....... about this

    What force makes them expand, The neutrons are all tightly packed but not in each other and they are all 0 charged and there is no reason for them to push apart from each other

    I would expect heat is the answer, the neutrons keep hitting each other like normal atoms behave in thermodynamics would neutrons behave like normal atoms?
  8. Mar 29, 2011 #7

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    Which force would make the neutron matter explode?

    There's no electric charge and the other 3 types of forces should still keep it together shouldn't they?

    [EDIT]I guess that since there speed would be zero they would have a temperature of almost 0 K, so they would absorb heat and push each other away from each other.[/EDIT]
  9. Mar 29, 2011 #8
    A sugar-cube-sized clump of neutron star matter would weigh more than Mt Everest. In your example, you describe a baseball-sized clump. So, for sake of argument, your baseball would comprise an amount of matter exceeding 20 Mt Everests (sea level to tip). As described above, the neutrons are so densely packed that when transported to normal conditions they will expand violently. In this case, they would expand with force far greater than a nuclear bomb, and would suddenly convert to matter 20 times larger than the asteroid that wiped out the dinosaurs, expanding at millions of miles per hour. Your transporter experiment would probably wipe out life on earth.

    BUT, if you could somehow build a container for it, it would probably sink into the crust, albeit quite violently. I would think it would fall to the center of the earth eventually (I can't imagine it ever going UP through a lava tube). There it would settle forever, assuming its gravity is shielded. If not shielded, I'm not sure how much of the core would stick to it. Would the earths core collapse around it? I'm guessing yes, but I'm not an expert.
  10. Mar 29, 2011 #9
    true... i'm pretty sure that it's just pressure in the form of heat tough, like when water boils it expands because of the atoms hitting each other
  11. Mar 29, 2011 #10

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    Perhaps we would have created the largest atom ever present on earth.
    It would have atom number 0.
    And the funny thing is that it might even be stable :rofl:

    [edit]Note that the weak and strong forces should keep it together.[/edit]

    [edit2]I agree that it would probably fall through the regular matter toward the center of the earth, where it would probably be oscillating for a while, since regular matter would be like vacuum or air compared to neutron matter.[/edit2]
  12. Mar 29, 2011 #11


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    It would be pressure, but not thermal pressure. Neutron degeneracy pressure would blow it apart.
  13. Mar 29, 2011 #12

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    If found the following passage at http://en.wikipedia.org/wiki/Neutron_degeneracy_pressure" [Broken].

    "Degenerate matter is matter which has such extraordinarily high density that the dominant contribution to its pressure is attributable to the Pauli exclusion principle.[1] The pressure maintained by a body of degenerate matter is called the degeneracy pressure, and arises because the Pauli principle prevents the constituent particles from occupying identical quantum states. Any attempt to force them close enough together that they are not clearly separated by position must place them in different energy levels. Therefore, reducing the volume requires forcing many of the particles into higher-energy quantum states. This requires additional compression force, and is made manifest as a resisting pressure."

    This seems to imply indeed that the neutron matter would explode forcefully, which also means it would not sink to the center of the earth.
    Last edited by a moderator: May 5, 2017
  14. Mar 29, 2011 #13
    you're absolutely correct in that electromagnetic forces prevent matter from moving directly through other matter. i did not mean to imply that the density of a degenerate mass of neutrons would be the direct cause of its tendency to fall through the ground and continue downward toward the center of the earth. its high density simply implies a vary large mass contained in a very small volume. the direct cause of its tendency to penetrate the ground would be the pressure exerted by the degenerate mass on the ground. for something that weighs as much as a mountain, its weight must be relatively evenly distributed over an area approx. the size of the footprint of a mountain. in this context, its high density implies a very large mass distributed over a very small surface area, and therefore would exert a very high pressure on the ground.

    in regards to what would make them expand rapidly, i'm second-guessing my initial thoughts. after considering that 1) neutrons have no charge and thus don't repel each other like protons do, 2) the strong force must be accounted for, and 3) neutron degeneracy pressure must be accounted for, i think the important thing to remember is how the neutron star became a neutron star in the first place - b/c extreme compression of a supernova, and then extreme gravity, forced lots of protons and electrons so close together that they had to combine to form neutrons. so while neutron degeneracy pressure will keep them from compressing and collapsing even further, compression from a supernova, and then extreme gravity, has already forced them close enough together for the strong force to take over and contain them like one giant nucleus of an atom. now i suppose if the strong force were to all of the sudden vanish, then i can see neutron degeneracy pressure forcing the neutrons apart violently. but otherwise, wouldn't they remain in a super dense, degenerate state? i don't know where i stand on this one...
  15. Mar 29, 2011 #14


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    The neutron star matter isn't held together by the strong force - it's held together by gravity. Without the extreme gravitational compression present on a neutron star, the neutrons would be forced apart extremely violently by the neutron degeneracy pressure, and the strong force would not prevent it.
  16. Mar 30, 2011 #15
    could you elaborate on that? are the neutrons in degenerate matter packed any tighter/closer together than the neutrons and protons of an atomic nucleus?
  17. Mar 30, 2011 #16

    So i read the wiki article, and it said that neutrons have neutron degenerate pressure,

    It said that neutrons had no definite space and jumped around like electrons? wtf was that since when did neutrons behave like electrons and have wawelengths. I would suppose that neutrons aren't point particles but according to this article they are?
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  18. Mar 30, 2011 #17

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    All matter including electrons and neutrons does not really behave as particles, but as probability distributions. This is the heart of quantum physics.

    In other words, neutrons aren't globes of matter that are packed together, but they are probability distributions which describe where you can expect to find them if you look.
    These probability distributions are usually modelled with wave functions (see http://en.wikipedia.org/wiki/Wave_function" [Broken]).
    The probability to find a particle in a specific volume of space is given by:

    More specifically, according to Einstein, mass and energy are the same. So a photon has mass (given by E = h f= m c2, where f is the wave frequency), but by the same token neutrons behave like wave energy with a frequency that is derived from the same formula. Note that the corresponding wavelength is extremely short compared to regular radiation.
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  19. Mar 30, 2011 #18
    If you were to go and fetch .
    Would that depend on how you fetched, instantly or gradualy.If you did it gradualy would the reverse of how the neutron star matter formed in the first place happen.Nothing too explosive just a gradual expansion.If it's gravity that holds it together would the slow removal of gravity as you moved the matter slowly away from the star just result in a non - spectacular expansion.
  20. Mar 30, 2011 #19

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    Now that I think about it, I just remembered that neutrons are not stable (see http://en.wikipedia.org/wiki/Free_neutron#Stability_and_beta_decay").
    They have a half-life of about 10 minutes (if they are free), splitting into a proton, an electron and a neutrino. Of course in a normal atom, the reverse occurs as well.

    Either way, it's possible that the neutron matter would decay into proton-electron matter, which might make it break up into regular atoms. As yet I have no idea whether this would be explosively or gradually.

    [edit]Actually I do not think it's just gravity keeping it together. It's just gravity that initially brings it together. But once the protons and electrons have collapsed into neutrons and they are packed together, the weak and strong forces will keep them together as well.[/edit]
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  21. Mar 30, 2011 #20


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    I doubt it. Otherwise you wouldn't have radioactive nuclei from neutron capture.
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