Recent content by HowardTheDuck

I can see that if you simply multiply the 4πr2 by the GM/r2 then you get the right answer. But I don't see how that's a valid thing to do. I don't see how it's valid to multiply dV/dr by d2r/dt2 (by the chain rule?) to get the right answer. Any help appreciated.

Hi Guys, I'm reading Roger Penrose's book "The Road to Reality" at the moment and I wonder if you could help me out with a pretty simple derivation which he doesn't describe in complete detail. On page 399 he considers a sphere of mass contracting under gravity, and says "The rate of volume...

Hi, I was wondering if someone could please check this, my current understanding of electron chirality and charge, just to see if I'm wrong at all. Thanks a lot. All electrons have left-handed chirality. Helicity, in the other hand, is observer-dependent, the way you look at the chirality...

"Identical" here means fermion type. This means, for example, if you exchange two electrons then the wavefunction of the system of those two electrons is multiplied by -1. The electrons could, therefore, not have been in a completely indistinguishable initial state (as you say, same...

Jilang's correct. Exchanging identical fermions multiplies the wavefunction by -1. This leads to the Pauli exclusion principle. You are free to exchange identical bosons at will - nothing changes.

I would say that the basic principles of quantum physics have not changed much since the early decades of the 20th century. De Broglie's picture basically became the Schrodinger equation, still in use today. I could say the integer wavelengths represent energy eigenstates, but it's basically...

Thanks. So that appears to suggest that, yes, if you are rotating in SU(2) then your objects behave as spinors. Yes, that's surely correct.

According to Louis de Broglie, particles can act like waves. Therefore, an electron orbiting a nucleus could be interpreted as a standing wave, with only an integer amount of wavelengths being allowed. Higher energy electrons can pack more wavelengths into their orbit. The longest wavelength is...

Hi, a fairly quick question. I'm reading Bruce Schumm's book "Deep Down Things" and he says that in SU(2) you have to rotate by 720 degrees to return to your starting point. This is clearly the same definition as a spinor. My question is, then, does rotation in SU(2) automatically imply the...

Here's my take on it. I''ve read about a bowling ball analogy for inflation. Inflation says our visible universe is only a tiny fraction of the true size of the universe which lies outside our visible universe. If you consider a bowling ball, it obviously has a great deal of curvature. That's...

Thanks for your response. But you don't consider inflation. Like I said, inflation guarantees a flat universe - no matter what the matter/energy/lambda values. That's the great appeal of inflation. It always guarantees flatness. Or am I wrong?

Thanks for your reply.

Hi guys, I have a question about the mass of the universe, and inflation/dark energy. As I am sure you know, inflation is supposed to stretch the universe so that the visible universe is only a small part of the true size of the universe. This guarantees that the visible universe is flat...

Yes, I think I have a much better understanding now. We might only be seeing a fraction of the total universe. The Hubble telescope is just looking at the only galaxies whose light has had time to reach us. The universe can expand much faster than the speed of light, so there can indeed be a...

Thanks for your help. I just think the distant galaxies look different. They look less formed, more basic. Like I said in that quote from Wikipedia "a considerably larger proportion of disturbed and irregular galaxies than the local universe". You said: "If you would have been able to capture...