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Here's something that just popped into my head: If we could instanly beam a sugar-cube of Neutron Star material to earth (using the same measurements as in the

Here's something that just popped into my head: If we could instanly beam a sugar-cube of Neutron Star material to earth (using the same measurements as in the article) what would happen to it? Would it just fall right through whatever it's sat on or would it instantly expand into something less dense?

Tepix 7y ago
I'm curious as well. My guess is it would expand because there's not enough mass left to overcome the strong nuclear force.
- imInGoodCompany 7y ago
  Not a physicist, but: "expansion" is probably understating it. My guess would be something analogous to an insanely powerful neutron bomb. Interesting thought experiment, would love to see someone do the actual maths.
  - SiempreViernes 7y ago
    "Neutron bomb" just means a nuke that releases a lot of neutrons while not exploding quite as much. The energy density contained within a bit of neutron star matter makes a big explosion, and that will likely dominate over the more exotic processes.
  - vman81 7y ago
    A 10cm3 cube of neutron star would weigh about a billion tonnes, comparable to a cubic km of water ice. I wonder how all that mass would behave if left to expand with all the exotic physics involved - if it would just sort of... vaporize the planet.
kmm 7y ago
With the confining pressure of gravity gone, it would instantly and violently expand. The intense 10^32 pascals of degeneracy pressure drop quickly with expansion, but even just assuming it can expand 5 ml at that pressure, the energy released would be 5e26 joules. That's about 1000 times the asteroid that made the dinosaurs extinct. It would certainly imply the end of all multicellular life. If somehow you could keep it confined, it would drop through whatever it was put on, through the entire Earth, and pop up at the other side. I suppose it would keep oscillating and eventually settle in the core.
- _Understated_ 7y ago
  Blimey. So I'd probably not even notice someone had teleported it here in the first place as I blinked out of existence :) Ok, on that note... what would it expand as? I mean, would it be a physical substance, like particles of something like a gas or a plasma? I assume it'd be quite hot (putting it mildly!)
  - posterboy 7y ago
    It would be sugar, obviously. A solar system sized Cotton Candy Cloud. Hey, I didn't start this sweet analogy.
  - jerf 7y ago
    It will cool into conventional matter eventually, but it would pass through a lot of exotic phases in between. I'm not sure we can even really answer that question, but here's something to give you an idea of what I mean: https://en.wikipedia.org/wiki/Quark%E2%80%93gluon_plasma https://en.wikipedia.org/wiki/Quark%E2%80%93gluon_plasma I'm not sure it would necessarily pass through that, but it would at least make a decent pass at it in those first few nanoseconds. If kmm's guesstimate of 5e26 joules is accurate, we're well beyond "extinguishing multicellular life" and in the realm of eliminating Earth entirely, which requires a minimum of 5.97e24 joules: https://en.wikipedia.org/wiki/Gravitational_binding_energy https://en.wikipedia.org/wiki/Gravitational_binding_energy 1% efficiency of transfer to the Earth is probably attainable.
    - kmm 7y ago
      I think you might have mistaken the Earth's mass in kg with the gravitational binding energy. That last one is 2.5e32 J. So about a millionth of the neutron sugar cube.
      - jerf 7y ago
        facepalm Urf, I was right the first time. Oh well.
- 7y ago
ekimekim 7y ago
Randall Munroe (author of xkcd) addresses this question in his excellent book "What If?", covering what would actually happen (basically a nuclear explosion), what would happen if it was somehow kept magically at the same density without exploding (it will end up oscillating around then settling at the Earth's core), and finally and most interestingly what it would be like if you could keep it near the surface and attempted to approach it.
imvetri 7y ago
we can use it as a gravity gun
- ASalazarMX 7y ago
  "Mr. President, we finally finished our gravity gun project! It only fires inwards, so we have to convince the enemy to invade the Earth's core first".
linksnapzz 7y ago
As I understand it, there is some speculation by observers at LIGO/VIRGO that two neutron stars colliding with each other may eject neutron-degenerate matter into space before they coalesce into a single new compact object. Not sure what that ejecta would look like...but if I had to guess, it would be release a shitload of energy as it came out from under compression, and would eventually condense into normal matter, much of it comprised of the sort of heavy elements not easily created via stellar nucleosynthesis. Imagine a cloud of incandescent radioactive gold dust weighing as much as multiple earths, and you've got the idea.

Tepix 7y ago

I'm curious as well. My guess is it would expand because there's not enough mass left to overcome the strong nuclear force.

imInGoodCompany 7y ago
Not a physicist, but: "expansion" is probably understating it. My guess would be something analogous to an insanely powerful neutron bomb. Interesting thought experiment, would love to see someone do the actual maths.
- SiempreViernes 7y ago
  "Neutron bomb" just means a nuke that releases a lot of neutrons while not exploding quite as much. The energy density contained within a bit of neutron star matter makes a big explosion, and that will likely dominate over the more exotic processes.
- vman81 7y ago
  A 10cm3 cube of neutron star would weigh about a billion tonnes, comparable to a cubic km of water ice. I wonder how all that mass would behave if left to expand with all the exotic physics involved - if it would just sort of... vaporize the planet.

kmm 7y ago

With the confining pressure of gravity gone, it would instantly and violently expand. The intense 10^32 pascals of degeneracy pressure drop quickly with expansion, but even just assuming it can expand 5 ml at that pressure, the energy released would be 5e26 joules. That's about 1000 times the asteroid that made the dinosaurs extinct. It would certainly imply the end of all multicellular life. If somehow you could keep it confined, it would drop through whatever it was put on, through the entire Earth, and pop up at the other side. I suppose it would keep oscillating and eventually settle in the core.

_Understated_ 7y ago
Blimey. So I'd probably not even notice someone had teleported it here in the first place as I blinked out of existence :) Ok, on that note... what would it expand as? I mean, would it be a physical substance, like particles of something like a gas or a plasma? I assume it'd be quite hot (putting it mildly!)
- posterboy 7y ago
  It would be sugar, obviously. A solar system sized Cotton Candy Cloud. Hey, I didn't start this sweet analogy.
- jerf 7y ago
  It will cool into conventional matter eventually, but it would pass through a lot of exotic phases in between. I'm not sure we can even really answer that question, but here's something to give you an idea of what I mean: https://en.wikipedia.org/wiki/Quark%E2%80%93gluon_plasma https://en.wikipedia.org/wiki/Quark%E2%80%93gluon_plasma I'm not sure it would necessarily pass through that, but it would at least make a decent pass at it in those first few nanoseconds. If kmm's guesstimate of 5e26 joules is accurate, we're well beyond "extinguishing multicellular life" and in the realm of eliminating Earth entirely, which requires a minimum of 5.97e24 joules: https://en.wikipedia.org/wiki/Gravitational_binding_energy https://en.wikipedia.org/wiki/Gravitational_binding_energy 1% efficiency of transfer to the Earth is probably attainable.
  - kmm 7y ago
    I think you might have mistaken the Earth's mass in kg with the gravitational binding energy. That last one is 2.5e32 J. So about a millionth of the neutron sugar cube.
    - jerf 7y ago
      facepalm Urf, I was right the first time. Oh well.
7y ago

ekimekim 7y ago

Randall Munroe (author of xkcd) addresses this question in his excellent book "What If?", covering what would actually happen (basically a nuclear explosion), what would happen if it was somehow kept magically at the same density without exploding (it will end up oscillating around then settling at the Earth's core), and finally and most interestingly what it would be like if you could keep it near the surface and attempted to approach it.

imvetri 7y ago

we can use it as a gravity gun

ASalazarMX 7y ago
"Mr. President, we finally finished our gravity gun project! It only fires inwards, so we have to convince the enemy to invade the Earth's core first".

linksnapzz 7y ago

As I understand it, there is some speculation by observers at LIGO/VIRGO that two neutron stars colliding with each other may eject neutron-degenerate matter into space before they coalesce into a single new compact object. Not sure what that ejecta would look like...but if I had to guess, it would be release a shitload of energy as it came out from under compression, and would eventually condense into normal matter, much of it comprised of the sort of heavy elements not easily created via stellar nucleosynthesis. Imagine a cloud of incandescent radioactive gold dust weighing as much as multiple earths, and you've got the idea.