Last year we had a new way of seeing the universe ... something that Einstein's equations predicted, but so difficult to detect that he said it would never been seen. Almost exactly a century after he published his General Theory of Relativity the first real detection of gravity waves was made. It is a leap on the order of Galileo's telescope.
This year's prize is more down to Earth, but exciting in its own way for physics and sociology. It went to three people - half to Arthur Ashkin for optical tweezers and the other half jointly awarded to Gérard Mourou and Donna Strickland for their technique to generate ultra short laser pulses.
I'll start with the first.
You've probably seen the demonstration where you take a hair dryer and points the stream of air towards the ceiling. Then you float a ping pong ball in the stream. Neat, but the wicked fun part is when you tilt the stream and the ball doesn't fall out. I've done it with a leaf blower and a volleyball. I won't get into the physics other than to note almost every science museum I've seen with a demo gets the explanation wrong. At a high level there's a restorative force on the ball when it moves to the boundary of the stream. If you've never seen it find some ping pong balls and a hair dryer. Remember to set it on cold:-)
An interesting feature of light is it has momentum. Shine light on something and you transfer a bit of momentum unless the object is perfectly transparent. The forces involved are small, but you can make sails that catch the momentum of sunlight to move a spacecraft. With powerful laser beams you can also move small particles on Earth. (.. those radiometers with the silvered and black paddle wheels that spin when light shines on them more for another reason)
It turns out you can trap very small particles in a narrowly focused beam of laser light. The forces are different from the hair dryer and pingpong ball, but the principle is similar. There's a restorative force when the small object gets to a boundary. Arthur Ashkin played around with this beginning in the early 70s at Bell Labs and figured out how to make it work well enough to manipulate biological objects like cells. As it became an important tool, another Bell Labs guy - Steve Chu - worked to extend the technique. His leap was to sort individual atoms by how fast they move. He could take a sample of very cold gas molecules and separate out a slower moving subset .. slowing them further in the process.. In other words he was cooling them. This revolutionized lower temperature physics and a few other fields resulting in Steve being sprinkled with the Swedish holy water a few years ago. Later he became Obama's science advisor.
I was surprised Ashkin never got the prize as it was fundamental to Chu's work and had make an impact on biology and some other fields. It was a pleasant surprise to hear his name today because that meant he was still alive, He's 96 and apparently didn't want to be bothered with interviews because he's working on a paper and has a deadline to meet.
And now to the other half of the prize. It's special in it's own right.
You probably had to memorize the speed of light as 186,000 miles per second -- or 3 * 108 meters per second if you took physics or aren't from the US. Big numbers are hard to grasp. In some of physics and electrical engineering a more natural unit is some fraction of a billionth of a second - a nanosecond. In a vacuum light travels about a foot in that time.1 We used to add physical delays to signals in our experiments by running signals through small lengths of coaxial cable - eight inches is a nanosecond in coax. Which is why some financial types use microwaves rather than fiber optics to communicate over distances of a few hundred miles. It's also why cloud computing has some fundamental issues.
Very short pulses of light are useful for studying biology, chemistry and physics. Here's another scale ..
a fast camera shutter captures light at the millisecond level (a thousandth of a second)
many chemical reactions are on the order of a millionth of a second .. microseconds,
switching times in computers are on the billionth of a second level - nanoseconds light travels about 30 centimeters
molecular vibrations are picosecondish.. a thousand of a billionth of a second. light travels about 0.3 millimeters
photosynthesis has some extremely fast aspects as does liquid water . think a millionth of a billionth of a second .. or femtoseconds. light travels about 0.3 microns
a billionth of a billionth of a second - an attosecond is appropriate for some of the slower subatomic motions. light makes it across most of what we'd call the size of a hydrogen atom.. but not by much
It's easy to get down to nanoseconds with electronics. Strickland and Mourou made it much more practical to work in femtoseconds and work down to attoseconds. Switching things on and off so quickly is very complex and their method is beautiful and simple. Describing it is tricky as it's nonlinear optics at the core, but it has had a huge impact on pure and applied research. It also might be used to create a relatively inexpensive way to accelerate protons and ions to energies high enough to be used in cancer treatment. Currently these techniques are very expensive, but more effective than tradional radiation treatments. There's a potential to work on organ tumors while the organ is moving with very little or no damage to nearby organs and much more disruption to the tumor DNA. That's probably worth another blog post.
And now the neat part. Donna Strickland is Canadian (University of Waterloo) and female. She's only the third woman to win a Nobel Prize in Physics. (you can probably guess the first.. I think only physicists will know the second). Thirty years ago women were in the single digits in physics Ph.D. programs. Now it's up to over twenty percent. That's still far too low and there are ugly stories. But it's finally changing.
She was Mourou's grad student and the prize winning work was her first published paper! I think that's unique in science.
From this morning and worth listening to:
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1 It's hard to grasp what a billion is. A reasonably close approximation of the seconds in a year is pi * 107. You're just over a billion seconds old when you turn 32.
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