What Did Chu Do?

Second Life avatar that is definitely not Dr. Steven Chu

There are idiots in this world who are actually more impressed by a Super Bowl ring than a Nobel Prize in physics. Fortunately, when the White House needed to appoint a Secretary of Energy in 2009, staffers tossed aside the résumés of grossly under-qualified NFL quarterbacks and selected Dr. Steven Chu, Director of the Lawrence Berkeley National Lab. Chu received a Nobel Prize for his work in 1997... but what exactly did he do to get it? What did Chu do?

First off, it should be noted that what he did, he didn't do alone. Chu shared the prize with two other physicists -- William D. Phillips of the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland and Claude Cohen-Tannoudji of l'École Normale Supérieure in Paris -- and all of them were no doubt assisted by a small army of physics graduate students and postdocs. Science is rarely a solitary endeavor these days.

Chu and company were recognized for perfecting a process called "laser cooling." Most people hear the word "laser" and immediately think of heat rays burning or melting or slicing through things... or just projecting little red dots onto PowerPoint™ presentations. On a human scale, lasers that have been configured a certain way can do those things. On the subatomic scale, a laser beam is just photons, little particles of light with a few distinguishing, but very important, characteristics. Including the ability to make things cold.

Understand what is meant by "cold" here -- temperature is really a measure of how much energy something has. Hot things have lots of energy and their atoms and molecules move around a lot. Cold things have less energy and their atoms and molecules move around less. The temperature in the Arctic during winter can go as low as -35° Fahrenheit. As cold as that is, atoms still have quite a bit of energy at that temperature. What Chu was concerned with were atoms of gas that were chilled to almost "absolute zero," the point at which atoms have so little energy they stop moving. We're talking temperatures around -459.67° Fahrenheit or -273.15°centigrade, just a mite's breath above absolute zero (0° Kelvin, that is, a less common unit of measure for temperature commonly used by scientists). Studying atoms is a helluva lot easier when they stay still and Chu and his crew figured out a way to make them do that.

Imagine this: You're in a long hallway with a bowling ball. You take aim and throw the ball, sending it rolling toward the other end. Now imagine, at the opposite end of the hall, there's one of those machines that shoots tennis balls and it's firing them at the bowling ball rolling towards it (and it's shooting with such precision that the tennis balls hit the bowling ball almost every time). If only a few tennis balls hit the bowling ball, and they don't hit it hard enough, the bowling ball will just keep rolling forward. If the tennis ball machine is on rapid fire and the bowling ball is getting struck with enough fast-moving tennis balls, they can make the bowling ball move backwards. However, if the machine is set just right, just enough tennis balls will hit the bowling ball to make it stop and keep it from rolling further down the hall. You're using tennis balls to stop the forward momentum of the bowling ball... not so many that it goes backwards, and not so few that it doesn't stop... just enough to keep the ball where it is. Substitute "gas atom" for "bowling ball" and "photon" for "tennis ball" and that's pretty much what laser cooling is.

What Chu and other scientists figured out was that you can slow down and even stop gas atoms if you shoot photons at them under the right conditions. Basically, the atom absorbs and re-radiates the photons that hit it, which robs the atom of its momentum. But just as you have to fire the right number of tennis balls at a certain rate to make the bowling ball stop rolling without going backwards, the photons that hit the atom have to have just the right frequency to make the atom lose its momentum and stop. Atom loses momentum, atom stops moving... atoms stop moving, atoms are now cold. If you had been the first to figure out what kind of atoms to use, what kind of light/photons to use and all the mathematics that goes with to allow others to repeat what you did, you'd have gotten a trip to Stockholm and a nice, fat check like Steven Chu and his colleagues did (a number of years after their actual discovery, it should be noted).

And what of Dr. Chu? Who is he? What makes him tick? Well, he was born in blah and raised in blah blah and first went to the toilet all by himself like a big boy in blah blah blah... Who cares?!? Does this look like TMZ or Us magazine? This is about the science, not the Chu. Suffice it to say he doesn't attend Klan rallies or make blood sacrifices to the demon-god Trigon, so we can be pretty sure he's mostly an okay guy. Back to the good stuff.

Once folks knew how to cool and trap atoms, other clever people were able to run with it and, in 1995, discovered a whole new form of matter. We all learned in school about the states of matter -- solid, liquid and gas -- but the count doesn't end at three. Heat something up enough (i.e. give it enough energy), and it can enter another state of matter: a plasma (that flame on the end of a lit match, for example). Now, thanks to some researchers at NIST, we also know that if you cool something down enough, down to a few millionths of a degree above absolute zero, you get another form of matter called a Bose-Einstein Condensate named after the two scientists who first discussed the existence of super cold forms of matter in the 1920s, Satyendra Nath Bose and our old friend Albert Einstein.

So what good is laser cooling?

Chu and his friends figured out an important incremental step in our ability to control matter that greatly helps scientists studying how atoms work. It's the kind of technique that's useful for investigating things like superconductivity and quantum computing, things that could mean future generations never having to worry about where their next joule of energy is coming from or how to fit another million songs on their iPods. Laser cooling itself probably won't lead to new products in your home, but it will be a big help to the researchers who will make the discoveries that will translate into new products for your home (or, more likely, your grandkids' homes... imagining a 4 gigabyte iPod that fits on a contact lens and lets you change songs by blinking).

To summarize:

Professional football -- unimportant.

Steven Chu's toilet training -- unimportant.

TMZ and Us magazine -- supremely unimportant.

Figuring out how to make atoms less fidgety -- really, really, really important.

Watching the "Jonny Test" marathon on Cartoon Network instead of thoroughly proofreading your blog posts before you publish them -- judgment call.

Priorities, people.

Again, not Chu.

References

• Absolute Zero and the Conquest of Cold by Tom Shachtman. ©1999. Published by Houghton Mifflin Co.
• Gould, Phillip L., Paul D. Lett, and William D. Phillips. "Cooling, stopping, and trapping atoms." Science 239.4842 (1988): 877+. General OneFile. Web. 13 May 2012.
• Chu, Steven. "Cold atoms and quantum control." Nature 416.6877 (2002): 206+. General OneFile. Web. 13 May 2012.
• Burnett, Keith, et al. "Quantum encounters of the cold kind." Nature 416.6877 (2002): 225+. General OneFile. Web. 13 May 2012.
• Canadian Journal of Physics 89.1 (2011): 25+. General OneFile. Web. 13 May 2012.
• Southwell, Karen. "Ultracold matter." Nature 416.6877 (2002): 205. General OneFile. Web. 13 May 2012.
• Taubes, Gary. "Physicists create new state of matter." Science 269.5221 (1995): 152+. General OneFile. Web. 13 May 2012.
• Vogl, Ulrich, and Martin Weitz. "Laser cooling by collisional redistribution of radiation." Nature 461.7260 (2009): 70+. General OneFile. Web. 13 May 2012.