Friday, January 27, 2006

Trap Day

Day before yesterday, Ken got a trap.

Yesterday he got it again, only bigger and brighter.

Yay! Hooray! You're cheering, right?

No, you're asking "What's a trap, and why does it matter?" That's the problem with achievements in a field like this -- any specialized field, I guess.

A "trap" is a small collection of atoms held suspended in mid-air -- except actually there can't be any air in the system or it won't work. A small collection of atoms held suspended in mid-vacuum. They aren't touching anything at all. They are surrounded by almost perfect nothingness. What holds them up? Laser beams, and a magnetic field.

The technical name for it is a "magneto-optical trap." You can actually see the atoms hovering there, a small glowing spot a few millimeters to a centimeter in diameter. You can see them because the lasers make them glow. In our case, they glow in the infrared, so you have to use a viewer to see the light, but here is a picture of someone's sodium MOT, that looks just like ours, only glowing with yellow light.

How does it work? Light actually does exert a force when it interacts with atoms. It can slow them as they come out of a nozzle. If you have light beams pushing up, down, left, right, forward, and back, it can keep atoms from escaping in any direction - it can trap them. Now the problem is to make sure that it exerts the right amount of force, and more, that the left-pushing beam only operates on atoms that are moving to the right, and not on those already moving leftward, and likewise for the other beams. This is where the magnetic field comes in. It changes the properties of the atoms, so that atoms in one part of the field interact with a different kind of light then atoms in the other part, and atoms further from the center are pushed harder than those near it. How do you calculate these forces and interaction energies? Um... Ask Ken. But give him time to go through his notes first.

The best explanation of laser cooling and trapping for the non-scientist (OK, and for the scientist as well. I personally need help turning the math into a conceptual picture) is at the University of Colorado's Bose-Einstein Condensate page. It's got little java videogames (hit "next" at the bottom of the page to see more), to let you try your hand at some laser cooling of your own. In our lab, we stop short of the "evaporative cooling" stage, and we don't get BECs. But we do get cold atoms.

What's nice about cold atoms is that they don't bump into each other so much, and they all have about the same velocity (close to zero). Any time you want to do an experiment that involves putting atoms into certain quantum states (you do this with lasers) -- you really want to do it in a trap, because if the atom collides with anything, your state is ruined. Also, you have to use different laser frequencies depending on the velocity of your atom, so if you can arrange for all the atoms to have the same velocity, you get better results.

So, Ken's project involves putting atoms into a certain quantum state, called the "dark state". You can control whether atoms in this state absorb light or not, and if they don't absorb it, what kind of "phase shift" they give it. (A phase shift just makes the peaks and troughs of the wave occur in different places.) This is supposed to be analogous to what some parts of a computer do to electronic signals and would supposedly be useful for some hypothetical quantum-computer, someday. Possibly. Maybe. Whatever. It means Ken is one step closer to graduating.

It's been a long, gruelling, frustrating process. The lab used to have a trap, and Ken worked on it, but with the departure of one of our post-docs, the whole shebang became Ken's responsibility. There are so many working parts to this, what with three lasers, at least nine different beams to align, electronics and optics to lock the lasers, frequency modulators, waveplates, beam expanders, magnetic coils, cooling water, and, oh yes, the vacuum. The pressure has to be on the order of 10^(-10) torr. Atmospheric pressure is 760 torr. Three different pumps, each with their own plumbing, their own gaskets, their own impossible-to-reach nuts and bolts. So many things have to work, all at once...

Only three people ever understood this system. The other two are now gone. Our former post-doc was able to consult a little, and I could help do the two-person jobs if he told me what to do (turn a knob at this end of the table to adjust a beam at that end. Turn the gas on and off to blow sealant through the coils, etc.) but Ken ran the operation, knew what had to be done, and succeeded.

So now you have enough information to understand what these pictures mean, scientifically and emotionally.

This is the vacuum chamber, in which the atoms are trapped. You can see a camera on the right-hand side.

This is what the camera saw. That bright dot at the center is the trap.

This is my attempt to take a picture through the viewer. The trap is very clear and bright, if you just look through, but it's hard to take pictures through an eye-piece. Anyway, click on the picture to enlarge it, and you can see it, a bright dot at the center of the small window.

This is what the vacuum gauge reads: 7.1*10^(-10). That's .00000000071 torr. Thank you, vacuum gods!

Monday, January 23, 2006

Son of Lunes Links

The funniest art story ever. I have to say this "performance art" cracks me up, which means I enjoy it, which means it's really art? Does the fact that it makes me think about whether it's really art, mean it's really art?

In memoriam for the Bears 2005 season: Shave Kyle Orton's neck beard. Via Ken.

A site that's been linked a couple of times by Jaquandor: Eyesore of the month. The month I link to is funny to me because it doesn't turn out to be the cemetary-strip-mall on Parker Road that I know.

Stop me if I've linked to this before:

Which reminds me: these recipes probably really will help you lose weight, if only by destroying your appetite.

That's all.

Saturday, January 14, 2006

The Toolmaker

I just read a book by Jill Patton Walsh, who is one of my favorite authors...

I first heard of her when she finished Dorothy Sayers’ unfinished novel Thrones, Dominions. I liked this enough to pick up her book about an atheist in a fantasy Inquisition-era Spain, called Knowledge of Angels. That one really got under my skin, with its portrayal of the suffering of a man of the sort I described in my last entry, a bishop whose faith is built on logic alone, when that faith is undermined by logical counter-arguments. So I read more. A book about aristocratic refugees in an imaginary Eastern European country, during and after their communist revolution (A Desert in Bohemia). A book about survivor guilt, years later, after a lifeboat accident (The Serpentine Cave). And then I discovered that she was primarily known for her children’s books. My university library had one. A story about a family who escapes Earth just before it is destroyed (The Green Book). A (true) story about a light-house keeper’s daughter who goes from isolation to celebrity after she rescues boaters. (Grace). A story about the fall of Byzantium (The Emporer’s Winding Sheet.) A story about the plague ( A Parcel of Patterns.) She is one of the least known of my favorite authors -- probably because she is still alive and writing. And she answered my e-mails a couple of times.

I wrote to her because some of the things she’d written were about women and academia (the Imogen Quy mysteries) and because she was clearly a Dorothy Sayers fan, and Dorothy Sayers was all about the kind of questions I was facing... After a year in grad school, I was starting to feel like I was wasting my time. I was starting to wonder if an academic career was really enough to give my life meaning. This was before I knew Ken (although I’d already seen him in our quantum mechanics class – okay, stared at him in quantum mechanics class – I figured he was way out of my league). The future I pictured for myself, if I stayed in grad school and kept on as I was going, was as bookish spinster. I didn’t really want that future. It didn’t seem like enough. I couldn’t imagine that I would ever do important enough work to justify my life by work alone. I certainly wasn’t doing it as a first year grad student. On the other hand, I didn’t really want to believe that I needed a husband and a family to make my life meaningful. Did I want to say Donna Reed’s life was more meaningful than Emily Noether’s? Did men need families to make their lives meaningful? Now, facing a much different future, I’m embarrassed by the memory of asking these questions of practically every woman I admired, or who was still single. Professors and authors. I put them in an uncomfortable position, and must have sounded hopelessly young. But Jill Patton Walsh was very gentle with me. I think she told me, more or less, that I was going to be disappointed if I was hoping for someone else to give my life meaning. But I couldn’t count on my work doing that for me either.

Okay, so the book of hers I just finished was called Toolmaker. It’s about a man in a prehistoric hunter-gatherer tribe who is better than his fellow tribesmen at making flint axes and arrow heads and so on. So they ask him to do it for them, leaving him no time to hunt. They bring him food. But he becomes too specialized, losing the ability to hunt for himself, and when times are lean, they are no longer interested in his toolmaking ability. He loses his status in his tribe. I won’t tell you how it ends. It’s a sort of parable, but you can take lots of different lessons from it... One of the most obvious being that it’s a bad idea to look down on your toolmakers, just because they don’t hunt. (Another being that it’s dangerous to become too specialized...)

Now, when you hear this story, who do you think of as the modern "toolmakers"? Are you thinking "intellectuals," scientists, professors, etc? ‘Cause I’m not. I’m thinking of the guys in the machine shop, who make the tools. The longer I stay in this field, the more natural the analogy of research scientist as hunter seems to me. (Their elusive prey? Grants.) And too often they do look down at the people who do the real, dangerous, and difficult work of shaping precision instruments capable of probing the smallest scales under the worst extremes of temperature, pressure, and in the presence of dangerous chemicals.

I finally started the machine shop class. The instructor has told us we should not hope to become machinists after only eight weeks (their apprenticeships last for years) but I am hoping to at least gain a better appreciation of what it takes. We spent the first day grinding a cutting tool that we will later use with the milling machine (I don’t know how or why, yet.) And we cut the our raw materials for our other products into rough outlines of the shapes we needed – and I do mean rough.

I still want meaningful work. In some ways the stuff I do in the machine shop seems more meaningful than the stuff I do in the lab. Ken says he felt the same, when he took the class. He misses that. But I also don’t want to rely on work alone to give my life meaning. The toolmaker in the book spends a lot of his time lonely, outcast, at one point, almost suicidal.

It’s so funny. I used to worry about this stuff, and think that what I needed was either to do something more important than homework, real research, or find a man, and I agonized over which was more important... Now I’m in a lab and I’m married, and I see that the problem never really had anything to do with either one.

Saturday, January 07, 2006

Logic and Faith

This discussion about evolution and religion on AFP (which I’m not posting to, because I’ve had this discussion enough times) got me thinking again about the appeal of religion for rational thinkers. The thing about science is, it forbids certainty. If you’re a good scientist, you have to be agnostic, not just about the existence of any gods, but about everything, including scientific theories, personal experiences, the evidence of your senses and the evidence of other people’s senses. You can’t be sure that you’re not just dreaming the rest of us. The refusal to take anything on faith leads to what one religious poster calls a “complete fog of unknowing” and a nonreligious poster admits is at least “fairly misty.”

This isn’t a fun position for rational thinkers, who presumably like to think rationally because it leads to conclusions which they can trust more than they can trust their wild guesses. In other words, they like to think rationally because they’re looking for some degree of certainty. But if you aren’t willing to accept the premises on faith, then you can’t accept the conclusions that follow rationally from them either. So people who are looking for answers ultimately have to rely on a combination of faith and reason.

The difference is in what kind of axioms you feel you can accept. What combination of direct personal experience, second hand reports, and consistency with your other experiences does it take to convince you that something is a fact? Scientists look for repeatable, recordable data. Religious people have to rely on subjective experience of God. (Since crazy people have subjective experience of their dogs talking to them, this is rarely convincing to anyone else. Scientists rely on subjective experience too, though, just not for reaching scientific conclusions.) And how willing are you to re-evaluate your position later? Scientists are supposed to only ever accept anything provisionally, always reserving the right to change their minds if contradictory data comes along. They'd like more certainty, but they have to leave room for new theories.

Some people aren’t satisfied with such wishy-washiness. They’re looking for truth without error bars and disclaimers. They want rock-solid foundations, none of this fog or mist, on which to build with iron logic, and religion provides that for them. There are more of these people than most atheists and agnostics think. There was a time when theology, not math or physics, was considered “queen of the sciences.”

It so happens that some of these people claim to have discovered, among other things, that those who reach the wrong conclusions about the way the universe works will meet terrible fates. (This is a testable prediction. Unfortunately, we can’t test it until we’re dead.)

The problem is, not all of these people agree with each other. They are not all of the same religion. So some of them must be wrong, must not have a handle on objective reality after all. Some of them might be right, of course, but how is it possible to tell which ones? Reason won’t help. The premises are the part of the argument you can’t prove, and that’s where they disagree.

The stakes are high, but you can't just pick the most likely sounding. It doesn't count if you say your god is "probably" the only one. That would defeat the whole purpose, which is certainty.

So those who don’t find any of assumptions self-evident, who would love to have rock-solid foundations but find only mist instead, might justifiably worry. (And they can worry about their friends of various religions, some of whom must be doomed if the others are right – even though none of those friends is worried for themselves.)

For those people: Monsignor Lorenzo Albacete says there is hope after all. Slate describes him as “a professor of theology at St. Joseph's Seminary in New York, and president of the Catholic University of Puerto Rico.” Slate says "But if God really loves humankind, shouldn't He let, say, a good Buddhist or Jew through the pearly gates? God goes further than that, says Monsignor Lorenzo Albacete in this clip from his interview: even atheists are eligible for salvation. This radical reinterpretation of scripture, Albacete notes later in the interview, has now become official Catholic doctrine (unbeknownst even to many Catholics)."

I didn't watch the whole interview, so I didn't find the part where he said it was official Catholic doctrine, but I did watch the part where he said atheists and Buddhists might have an easier time getting into heaven than he did. Not that they could get in on good works alone -- it doesn't count if you're doing them to impress someone or make yourself look good -- but if you did them out of love for your neighbor, did them out of faith, if not in Jesus, then in what Jesus stood for, they still counted. This sort of seems consistent with Catholic doctrine to me (although most protestants probably wouldn't like it.) Mind you, he doesn't say that those atheists and Buddhists aren't wrong, just that they won't necessarily be punished for their mistakes.

Monday, January 02, 2006


"Careers" by Robert Graves

Father is quite the greatest poet
    That ever lived anywhere.
You say you’re going to write great music—
    I chose that first: it’s unfair.
Besides, now I can’t be the greatest painter and
      do Christ and angels, or lovely pears
      and apples and grapes on a green dish,
      or storms at sea, or anything lovely,
Because that’s been taken by Claire.

It’s stupid to be an engine-driver,
    And soldiers are horrible men.
I won’t be a tailor, I won’t be a sailor,
    And gardener’s taken by Ben.
It’s unfair if you say that you’ll write great
      music, you horrid, you unkind (I sim-
      ply loathe you, though you are my
      sister), you beast, cad, coward, cheat,
      bully, liar!
Well? Say what’s left for me then!

But we won’t go to your ugly music.
    (Listen!) Ben will garden and dig,
And Claire will finish her wondrous pictures
    All flaming and splendid and big.
And I’ll be a perfectly marvellous carpenter,
      and I’ll make cupboards and benches
      and tables and ... and baths, and
      nice wooden boxes for studs and
And you’ll be jealous, you pig!