Thursday, March 30, 2006

car physics

In thinking about this question of whether accelerator physics is really physics, I think about the question of whether the problems facing car designers is physics. When you drive your car really fast, you want it to be a smooth ride. Is the systematic understanding of bumpiness in rapidly moving cars physics? Is it science?

I guess I would have to say the answer is maybe. The question is whether systematic approaches can be developed or not. That seems to be what we mean by science. The statistical mechanics of bumps in the road and the understanding of shock absorbers is applied physics. If one simply models the car in a really complex way, writing an elaborate computer program that simulates the effects of bumps, I would be more reluctant to call that physics. Coming up with simple models, finding what elements are essential and understanding that simplified model: that is what I would call physics.

The old joke about the physicists who starts out a calculation: "suppose the horse is a sphere..." that does seem to capture what we mean by physics in a way. It may be bad physics if one wants to understand how fast the horse can run, or how its surface to volume ratio relates to heat production, but the modeling aspect is physics.

Maybe physics has come to mean two distinct things. There is basic physics which relates to understanding of things in the extreme. Extreme simplicity, size- large and small, speed, complexity, etc. Then there is the process by which a system is replaced by a simplified model which is then analyzed. This is the sense in which accelerator physics is physics. I replace the complex of magnetic fields by a symplectic matrix. Quantum mechanics is ignored. The thoughts in the people nearby are ignored. The rising and setting sun is probably ignored.

Coming back to the car then, if you can think of it as a damped driven harmonic oscillator, then you are indeed doing physics. So I don't know how much interesting stuff has come out of car physics. But it does seem clearly meaningful to talk about car physics, even if the purpose is to design a better car.

What comes out of this definition of physics, however, seems to be that physics is not fundamental. It is an element of how we understand our world, a specific mode. It is not particularly descriptive. Listing the objects in a room is not physics, but it is a part of understanding the room. To take this a little further, one might say that physics is a language in which the world can be described. It asks the user to be very sparse in the number of elements of that description. One can use harmonic oscillators. One can use Hamiltonians. One can use random variables. One can use heat transfer and rigid bodies. From this language one will find that some things are quite difficult to describe.

You might argue that one always uses physics. If I say that there is a beer bottle and an apple core on my futon, you could ask: what do you mean by beer bottle and apple core? Don't you mean brown glass with colored labels and a spongy object which is a collection of cells and sugar molecules? The point is that I might not have these "scientific" descriptions at hand, yet I can still make myself understood by using the words "beer bottle" and "apple core". And beer bottle and apple core are really not words in the physics language.

Am I getting closer to understanding? I know one can go around and around in circles with these questions. But I do feel like this leaves me slightly closer to where I wanted to go.

Wednesday, March 29, 2006

science vs. technology

The topic of whether accelerator physics is really "physics" or even science is a sensitive one for me. Or at least an interesting one. Anyway, I found this discussion thread from a few months ago at Cosmic Variance, and decided to add a comment.

Sometimes it feels like an arranged marriage to me. I've decided on this field, and I'm trying my hardest to like it. To make it work. One solution is to work towards fitting it into the framework of physics that I know and love. This works for some of the work I do and a good amount of the interesting stuff in the field. But it also leaves out the more engineering aspects which I should probably understand. How do I deal with this? One way is to try to remove the stigma from the word "engineering". I read about the philosophy of engineering. I am happy to discover that engine and engneering have common origin, rather than one being derived from the other. Then there is the word technology. The phrase "evils of technology" flows more naturally off of one's tongue than does the "evils of science". Maybe the nuclear bomb and nanotechnology turning the world into a gray goo come under the latter, but the whole issue of quality of life in the modern world and our questionable attitude of finding high tech solutions to problems instead of looking at root causes seems to me more pervasive and has more resonance for me. So, I need to do some work in thinking about my attitude towards technology and engineering. The design of bridges or economies has never interested me that much. Why should I be involved in design of accelerators when I'm not interested in these other more prevalent things?

Yes. I'm ambiguous. Maybe its just exhaustion, but this does seem like a question I need to resolve at some point.

some photos

more interviews yesterday. Overall the talk went pretty well. I think I actually explained our approach to intrabeam scattering somewhat clearly.

The first of these photos is of the booster accelerator. I think that there's actually two rings in the same tunnel, the booster and the anti-proton accumlator which stores the anti-protons. Anyway, its an impressive operation getting all these protons and anti-protons up to close to 1TeV to collide in the Tevatron.

The second picture is Wilson hall. I think it was designed by Robert Wilson, the first director of Fermilab. From the top floor you can see all the different accelerators.

One of the interesting questions I was asked yesterday was whether I really care about things like the ILC (International Linear Collider) and the LHC (Large Hadron Collider). Its a question I've thought about. The short answer is that I want to care about them, but I'm not sure I do. Maybe I'll write more about it sometime.

Monday, March 27, 2006


My last interview today was in the 12th floor of Wilson hall. This was the first interview I've had that actually felt like an interview, where my thinking and abilities were being judged. This was the second Russian I spoke with. Lets call him Dr. S.
After I sat down, Dr. S reached into a back corner of his office on top of a filing cabinet and began to pull out a variety of objects one at a time. The first was a rock.

He placed it in my hands and asked me to tell him what it was. "Its a rock", I suggested. "Uh, it has some quartz in it?" I added, venturing into unknown teritory. "Yes," he responded noting the sparkles from the rock. He didn't leave me hanging for too long. "This was dug out of a mine over there," he said motioning out the window into the distance. "The ILC may be built on this. It looks ok, right? Pretty sturdy?"

The next item was a circular metallic ring. "What's this?" asked Dr. S. "Uh, a copper ring?" I replied. "Ok, but tell me about it. Why is it darker on the outside than on the inside?" "Oxydation?" It was an ok answer but showed I'd never seen such a thing. He explained that it was a connector between pieces of beam pipe. It had been heated to expell outside gas and the outside was in contact with the air and so turned black whereas the inside was in vacuum.

This carried on for about 10 items. I think I got one of them right. I tried to ask questions and at least show interest. He then asked me about the various research projects I'd done 6 years ago that I barely remembered the details of. I told him about the solenoid problem and then he asked me how fast the fringe fields fall off, which I couldn't answer.

I did get to explain a few things I understood and felt glad to be challenged and have my ignorance of the field out in the open. I know I wasn't as sharp as I can be, but hopefully I said at least a few useful things. Tomororrow I give my talk.

Saturday, March 25, 2006

global warming skepticism

At some point I plan to try to figure this stuff out.
This looks worthwhile.

Thursday, March 16, 2006


How many wars have been started because old friend the small frog disappeared, never to be seen again, without a word of explanation?

Wednesday, March 15, 2006

another movie

cracker jack ring engraved. zebra rugs.
"you look tres distingue yourself!"
(the first of these should give it away)
Now I remember where this genre comes from... its the annoying ads you see before movies in some theatres.

Sunday, March 12, 2006

ontology is overrated

I enjoyed reading this essay (talk) by Clay Shirky.
The part on search seemed to capture a change I'm somewhat familiar with but still adapting to.
The part on tags made me want to play around with these things and learn more.

Saturday, March 11, 2006

snow in san francisco!

Just a little bit left along the side of the trail of Lake Merced.
It was a refreshing snack during my run that had turned into walk.

Thursday, March 09, 2006

relieving tension

Sometimes it seems that the world is made of screens and text.

I am trying to relax. I know that there are things that my mind needs to do, that it won't do until I remove all the stimuli.
But what do I do during these times? One can call it meditation. Maybe wrestling with demons?

I suppose it is a privilege to be able to return to the ground state; to be able to cross this peak made of old thoughts. This is where evil can come from. When one is not allowed the time to return to where one came from. To keep the tension high for so long that one forgets what its like to not have it.

No. I refuse to see it as a privilege. Instead I see the lack of returning as sickness. But what about those of us who are slow? I suppose most societies find ways to accomodate. I don't know that ours has done this very well.