Thursday, May 24, 2012

A Picture from Work

I have the greatest job in the world! (While, apart from being the chair of the Math Department, but that's just for another year.) Having tenure at a great up-and-coming liberal arts university, and conducting nuclear physics research at the world's premier medium energy electron accelerator-- which is only a 10 minute drive from our campus! It is darn near a perfect situation.

The accelerator has gone quiet. Data taking has stopped for the next 18 months, after which will turn back on with twice the energy (12 GeV).

Everyone is getting ready. New detectors have to be built and new software written. One of my tasks is to write the event display software for Hall B, one of the four experimental halls: Hall A, Hall B, Hall C and Hall Tim. (Just kidding, Hall D.)

Here is a screen shot from version 0.1:

This shows one set of detectors for our experiment: drift chambers. This is a 2D slice (we also have 3D views) in which you can imagine the tilted 2D rectangles are actually tilted 3D boxes perpendicular to the page. Each box contains six layers of wires, with 112 wires per layer. The wires are also (roughly) perpendicular to the page. The wires are maintained at high voltage (to produce an Electric field) and embedded in a gas. After a collision at the target (roughly the lower left corner) the outgoing reaction particles go flying toward the detectors. Going through the gas they cause ionization, and the ions collect on the wire which then produces an electronic signal. That results in a rough set of locations of the track which, together with the magnetic field (shown as a "thermal" plot in the picture) allows us to determine the momentum (but not, by itself, the identify) of the particles.

What is show is a simulation (from GEANT4) which is why it is so clean (this simulation did not, in this instance, simulate background) and why we know "truth". That is, the particles are colored based on what type they are. In real data, prior to analysis, we wouldn't know one track was a pion, one a muon, etc.


And another:

Wednesday, May 23, 2012

Randall Munroe comes home

Randy Munroe of xkcd fame came back to his alma mater (CNU) in April, giving a fantastic talk. I am in the picture--but not up front.

Tuesday, May 22, 2012

Two Theologians on "How old is the universe?"

R. C. Sproul nails it. (Click on "the age of the universe" link on this page.)

Al Mohler blows it. He begins with an argumentum ad populum: well, lots of church fathers believed in a young earth! This is an especially specious argument because he never points out that they had no reason to believe otherwise. Had they held fast to a belief in a young earth in the face of overwhelming data to the contrary he'd have a point. Also, he is selective in what he draws from the church fathers, never pointing out that while they thought the who and the what of creation was important enough for the historic creeds, they didn't seem to care to much about the when. Nor did honesty incline him to point out that the early church consensus on a young earth extended to an early church consensus on a geocentric universe.

His arguments never improve.

He repeats, unabashedly, just about every dumb argument ever made. He criticizes "uniformitarianism" or the idea that the laws of physics have not changed. He never addresses the counter-argument: OK, let us, for the sake of argument, toss out uniformitariansim (even though there is zero evidence for doing so.) You are still left with a big problem. That might explain why the radiometric data are wrong. That might explain why the astronomical and astrophysical data are wrong. That might explain why the geological data are wrong. But it doesn't explain why the different radio isotopes give the same wrong answer, and it doesn't explain why the aforementioned astronomical, astrophysical, and geological data all give the same wrong answer.

One of the more obtuse arguments Mohler makes is that it is more or less unimaginable that (as OECs would claim--at least those who wish to preserve the historicity of Adam) God would intervene to specially create or ensoul Adam and Eve. This is bizarre--why would Mohler find it unimaginable for a God who created the universe to intervene, in what appears arbitrarily to us, at any time in history that it pleases Him?

Sproul gave an honest (and correct) answer. Mohler gave a dishonest reply, never mentioning the considerable flaws in his own arguments. I feel a little dumber after listening to his talk.