Neutron Stars and Black Holes
My five and half year old boy loves science too. He is currently infatuated with astronomy. He did get quite upset after he read that our solar system won't last forever and it took me a while to calm him down. Now he obsesses about neutron stars and black holes. These are truely mind-boggling stuff even for a quasi-physicist. When I studied physics my interest was mainly down on the earth. The other day he asked me what the temperature is inside the neutron stars and the black holes. This was beyond the encyclopedia he was reading, so we tried to look up the answer on the web. I can't say we got a straight answer.

This lecture note says the surface of the neutron star is 1000000 K. But it also says that it has crystalline iron crust. Hmm, is iron solid at this temperature? Because of the incredible pressure caused by the gravity? And how hot does it get inside for protons and electrons to get crushed into neutrons?

Black holes get even more confusing. This link first says:"It turns out that all the possible standing wave states are equally probable." Okay that seems to say that the temperature inside is infinite. But then it goes on to calculate the temperature to be: "if we measure the mass-energy M of a black hole in units where the mass of our Sun is one, then the absolute temperature of the black hole is 6 × 10-8 / M Kelvin". So now it says the temperature is at close to absolute zero. Ha! I am guessing that the second temperature is what appears to us. Since an ideal black hole would not let anything out it should appear to be at absolute zero. The little radiation loss due to QED makes it appear to have a wee bit thermal temp above zero. But how come inside the black hole its temperature is infinite? Simply due to the singularity? How does one reconcile the two?

I am asking an old friend who is an astrophysicist to see if he knows. If I get answers I will post them here.