Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: syhprum on 15/10/2006 09:06:13

Title: Density
Post by: syhprum on 15/10/2006 09:06:13

If I take Protons with a basic density of 2.5*10^14 Kg/liter, add a similar quantity of Neutrons with the same density and the same number of electrons with a much lower mass (1/1836) but quasi infinite density I end up with Deuterium with a density at low temperatures of about 100gms/liter.
What determines the density of stable matter ?

syhprum

Title: Re: Density
Post by: daveshorts on 15/10/2006 10:50:32

mostly the pauli repulsion of protons and electrons. They are known as fermions which means that two of them can't be in the same place with the same spin at the same time due to a property of their wavefunctions. Also because they are waves they are spread out over a certain volume related to their wavelength, so there is a limit to how small a volume you can put them in (this is larger for electrons than protons)

Title: Re: Density
Post by: lightarrow on 15/10/2006 12:20:30

I thought the main reason was Heisenberg indeterminacy principle, at least for what concern hydrogen or deuterium: the electron cannot be more near to the nucleus than a certain value because otherwise his momentum would become too high and it would escape from it: (delta)p*(delta)x >= h. So, if (delta)x decreases, (delta)p increases.

Of course there is still a non zero probability that the electron could be found in the nucleus (wave function; tunnel effect), but this doesn't change the essence of the reasoning.