UW Update 1/26/14: Wikipedia on Hinduism, Supernovas, and Judo

1.     UW Update 1/26/14

a.     Woke bright and early and headed out to physics. We discussed the strange phenomenon of magnetism, which is related to electric force but not really the same thing (after learning about electric force, I confused magnets with electric dipoles, but magnetism is fundamentally distinct).

b.     Planned to study outside, but realized I’d left my computer in the dorm. Ran back and researched for cow paper for a while—for a one-page paper, this was occasioning a lot of work. I was realizing how bad the Wikipedia articles on Hinduism were (a. Hinduism is fragmented, since India was never politically or culturally unified, and b. there may not be that many expert English writers who are also expert Hindus), and how multiple sources were often contradictory.

c.      Returned to physics complex for Lunchbox seminar with lunch from Motosurf. This one was really accessible and interesting. The professor, a theorist from Caltech, was interested in how to model supernova explosions. The reason that supernovas explode is really not well understood.

d.     Supernovas, play by play:

                                                 i.     When the star can no longer generate enough nuclear energy to stop itself from falling in under its own weight, or the star core of heavier elements gets large enough,

                                               ii.     The iron core at the center of the star starts to collapse. Why iron? Iron has the stablest and most densely packed nucleus of all the elements, and fusing two iron nuclei into larger elements takes more energy than it releases.

                                              iii.     The iron core gets so dense that electrons and protons fuse to become neutrons. This inner “neutron star” has a density of about 10^14 g/cm^2(!).

                                              iv.     At some point, the strong nuclear force, which is usually attractive, becomes repulsive, and the neutrons stop compacting. This sudden reversal in the effect of the nuclear force generates a shock wave that ripples back outward towards the infalling material. Now you have a neutron star, surrounded by a zone where the shock from the strong force is holding up the infalling material.

                                               v.     Now the neutrinos, obscenely tiny, massless particles generated in e- + p+ -> n reaction, come into play. Because when you have ~10^57 tiny, massless particles, they’re not negligible anymore.

                                              vi.     Normally, neutrinos pass through ordinary matter as though it weren’t there. But the neutron star is so dense that the neutrinos bounce around in the star before escaping.

                                            vii.     These neutrinos have two effects. First, they interact with matter in a part of the shock zone (the “gain” region because this is where the star is gaining energy from the neutrinos) and heat the matter. Second, if they get past the shock zone, they pull massive amounts of energy out of the star as the star’s gravity (yes, gravity works on massless particles if they’re moving fast enough) slows them down.

                                           viii.     There’s a one-second window before the escaping neutrinos pull too much energy from the star for the star to explode (I think this is how it works, my memory is not perfectly clear on this). In this time, the inner neutrinos must heat the region inside the star sufficiently to blow the star up. The problem is that calculations indicate that the neutrino heating is not sufficient, and that based on this alone supernova-sizes stars would not explode but collapse into black holes.

                                              ix.     This researcher’s idea is that turbulence in the gain region is supplying the additional energy, pressure against infalling material, required to blow the star up. I don’t understand how this works, but the fluid dynamics of the gain region cause the neutrinos to supply more energy in the gain region when turbulence is taken into account.

                                               x.     He’s running lots of simulations to try to understand how this works, since the math is almost impossible. Although computers don’t yet have enough computing power to model the supernova in high fidelity, they can model small regions in high fidelity and capture the complexities of turbulence effects.

                                              xi.     Crazy fascinating, right?!

e.     From the seminar, I went straight to my teaching class. We talked about the midterm paper (due shortly L) and brainstormed ideas.

f.      The sky was cloudless so I took a run to the arboretum across the Montlake Cut. It was very pretty.

g.     Returned to the dorm, studied for a bit, ate dinner at the 8, then went to Judo class. I’ll spare you the details of getting my locker combination, then having to re-figure out how the locks work. I can’t remember simple manual instructions.

h.     Learned some more falls, the initial fighting stance, basic footwork, and started to lead into throws.

i.       Returned to dorm listening to Serial, ate banana w/ peanut butter and gorp, and spent a long time finishing cow paper. Did laundry and email.

j.       Went to bed.