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12
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2answers
1k views

Is Pauli-repulsion a “force” that is completely separate from the 4 fundamental forces?

You can have two electrons that experience each other's force by the exchange of photons (i.e. the electromagnetic force). Yet if you compress them really strongly, the electromagnetic interaction ...
3
votes
1answer
240 views

A question about Pauli’s exclusion principle and electron orbital

According to Pauli’s exclusion principle, $s$ orbital contains at most two electrons with the opposite spin(up and down). Why can't $s$ orbital contain a third electron whose state is the linear ...
10
votes
2answers
270 views

Capactiy of an orbtial to hold muons and electrons

In a normal atom, there is a limit of 2 electrons per obital due to the Pauli-Exclusion principle. I have seen people talking about replacing an electron with a muon, but since muons and electrons are ...
0
votes
1answer
299 views

Why do electrons make a Fermi sphere?

In Sommerfeld theory for metals, after determining all of the possible levels for a single electron, one says that we build up a state for a system with $N$ electrons by filling up those levels, ...
2
votes
2answers
274 views

Why Pauli exclusion instead of electrons canceling out?

To quote Wikipedia, The Pauli exclusion principle is the quantum mechanical principle that no two identical fermions (particles with half-integer spin) may occupy the same quantum state ...
2
votes
1answer
204 views

In a neutron star - what force keeps the neutrons from getting closer and closer? [duplicate]

Possible Duplicate: Why do neutrons repel each other? What I mean is that the neutrons are attracted to one another via gravity, so what force keeps them from collapsing to form a "neutron ...
1
vote
1answer
268 views

Impervious nature of solid matter due to quantum degeneracy pressure

On Wikipedia the following statement is made without reference: Freeman Dyson showed that the imperviousness of solid matter is due to quantum degeneracy pressure rather than electrostatic ...
2
votes
1answer
307 views

Why are do neutral atoms shrink as their valence shells approach 8 electrons?

Why do neutral, unbonded atoms shrink in size as they approach having 8 electrons in their valence shells? A good example is elements 3 through 10 in this table, that is, lithium (1 valence electron) ...
2
votes
2answers
3k views

Why can't two or more objects exist at the same place at the same time?

Two objects with half spin would consist of the elementary particles (i.e. quarks, fermions etc.) which are waves. Therefore all objects consist of several waves. Waves can exist at the same place at ...
6
votes
1answer
965 views

Degeneracy Pressure, What is it?

There has been numerous question, some violent even in physics@SE regarding PEP and EM forces. But what baffles me is what is degeneracy pressure? I know there are 4 fundamental forces- EM, gravity, ...
3
votes
1answer
166 views

Do mass and the Pauli exclusion principle conspire to make light fermions take up more space?

The wavelength of light fermions is longer. Wouldn't this cause them to take up 'more space' so that they didn't overlap according to the Pauli exclusion principle? Am I totally misunderstanding ...
18
votes
10answers
10k views

Does the Pauli exclusion principle instantaneously affect distant electrons?

According to Brian Cox in his A night with the Stars lecture$^1$, the Pauli exclusion principle means that no electron in the universe can have the same energy state as any other electron in the ...
4
votes
5answers
3k views

If the earth has gravity, why don't we all collapse to the center?

I'm sorry if the answer is obvious for you guys, but why don't we all (including buildings, road, people, the ground) collapse to the center of the earth because of gravity? Is it because we have ...
7
votes
3answers
4k views

What is the cause of the normal force? [duplicate]

I've been wondering, what causes the normal force to exist? In class the teacher never actually explains it, he just says "It has to be there because something has to counter gravity." While I ...
6
votes
1answer
788 views

Is Palladium an exception?

I have been taught in school that atoms cannot have more than 8 electrons in the outer shell. Palladium atom's electron configuration is 2,8,18,18. Why isn't it 2,8,18,17,1 like the case of Platinum ...
7
votes
2answers
2k views

What causes the Pauli exclusion principle (and why does spin 1/2 = fermion)?

It seems to be related to exchange interaction, but I can't penetrate the Wikipedia article. What has the Pauli exclusion principle to do with indistinguishability?
58
votes
10answers
5k views

How can I stand on the ground? EM or/and Pauli?

There is this famous example about the order difference between gravitational force and EM force. All the gravitational force of Earth is just countered by the electromagnetic force between the ...
17
votes
7answers
3k views

Why do neutrons repel each other?

I can understand why 2 protons will repel each other, because they're both positive. But there isn't a neutral charge is there? So why do neutrons repel? (Do they, or have I been misinformed?) The ...