Collapsing Stars: White Dwarfs, Neutron Stars & Singularity

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In summary, the conversation discusses the properties of white dwarfs and neutron stars, specifically their low uncertainty in position but high uncertainty in momentum. It also mentions the concept of degeneracy in electron and neutron states, as well as the existence of singularities and their conflict with the uncertainty principle. The expert points out that singularities violate the uncertainty principle and are not allowed in quantum mechanics. They also mention the ongoing search for a theory that can unify quantum mechanics and general relativity. The conversation concludes with a brief discussion about the Pauli-exclusion principle and the properties of electrons in an atom.
  • #1
SpitfireAce
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White dwarfs and neutron stars have very low uncertainty in position (since the particles are practically on top of each other), but a lot of uncertainty in momentum, and thus the claustrophobic particles vibrate with great momentum creating an outward force to oppose gravity, but doesn't a singularity defy the uncertainty principle? All the stuff that used to be the star collapses to have a common position/time (a point of infinite density) and momentum/energy (all the mass-energy is infinitely compacted to that point)...
 
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Your understanding of electron and neutron degeneracy is incorrect. These forms of degeneracy have nothing to do with small uncertainties in position. After all, even a tiny neutron star is still enormous compared to subatomic scales.

Electron and neutron degeneracy are the result of all quantum mechanical states being filled. Since both electrons and neutrons are fermions, only one particle can occupy a particular quantum state.

Singularities absolutely do violate the uncertainty principle, In fact, singularities are not permitted in quantum mechanics at all. Quantum mechanics forbids singularities, while general relativity predicts them -- this is one of the reasons why these two theories are incompatible, and one of the reasons physicists are seeking a more general theory that will correctly unify them.

- Warren
 
  • #3
"only one particle can occupy a particular quantum state."
This sounds like the Pauli-exclusion principle, but I thought the underpinning behind the principle was uncertainty, if the electrons fell into the same state in the atom they would be defying uncertainty, my wave interpretation is that the energy levels are the different harmonics of standing probability waves possible, and the reason there is nothing in between is that if two probability waves overlapped it would mean there was a probability of two electrons with common position and energy/momentum, is this all correct?

I'm reading Feynman's lectures on physics and he tends to talk about electrons like little tennis balls bouncing around

I'm assuming by quantum states you mean energy level, sub level, orbital, spin ect.

thanks for replying =)
 

1. What is a white dwarf?

A white dwarf is a type of star that has reached the end of its life cycle. It is the remnant core of a low to medium mass star (about 0.08 to 8 times the mass of our sun) after it has exhausted all of its nuclear fuel and shed its outer layers. White dwarfs are extremely dense, with a mass similar to our sun but a size comparable to Earth.

2. How is a white dwarf formed?

A white dwarf is formed when a star runs out of fuel to burn in its core. As the star's core collapses under its own gravity, the outer layers are blown off in a planetary nebula. The remaining core, which is mostly made up of carbon and oxygen, becomes a white dwarf.

3. What is a neutron star?

A neutron star is a type of star that is even more dense than a white dwarf. It is formed when a massive star (about 8 to 30 times the mass of our sun) runs out of fuel and undergoes a supernova explosion. The core of the star, made up of mostly neutrons, collapses under its own gravity and becomes a neutron star.

4. How is a neutron star different from a white dwarf?

A neutron star is much more dense than a white dwarf, with a mass similar to our sun but a size comparable to a city. Neutron stars also have extremely strong magnetic fields and rotate very quickly, often spinning hundreds of times per second. In contrast, white dwarfs are less dense and rotate much slower.

5. What is a singularity?

A singularity is a point of infinite density and zero volume. It is believed to exist at the center of a black hole, where the gravitational pull is so strong that not even light can escape. The concept of a singularity is still not fully understood and is a subject of ongoing research in the field of astrophysics.

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