Experiment
drorzel | May 18, 2010There's a Dennis Overbye article in the Times today with the Web headline "From Fermilab, a New Clue to Explain Human Existence?" which I like to think of as a back-handed tribute to the person who linked to an interview with Sean Carroll by calling him "The cosmologist, not the scientist." This is the secret of human existence explained by science, not biology.
The physics issue in question is why we have more matter than antimatter in the universe, as symmetry would seem to demand they be created in equal amounts in the Big Bang. Had that happened, though, all of the matter should've…
drorzel | May 6, 2010There's a minor kerfuffle at the moment over the XENON experiment's early data (arxiv paper) which did not detect any dark matter in 11 days of data acquisition. This conflicts with earlier claims by the DAMA experiment and recent maybe-kinda-sorta detections by the CoGeNT and CDMA experiments.
As a result, a couple of members of other collaborations have posted a response on the arxiv saying, basically, that they don't believe the sensitivity claimed for the XENON detector in the energy range in question, and that their result can't really be said to rule out the possibility of dark matter…
drorzel | May 3, 2010Voting has closed on the Laser Smackdown poll, with 772 people recording their opinion on the most amazing of the many things that have been done with lasers in the fifty years since the invention of the first working laser (see the Laserfest web site for more on the history and applications of lasers). The candidates in the traditional suspense-building reverse order:
Lunar laser ranging 22 votes
Cat toy/ dog toy/ laser light show 41 votes
Laser guide stars/ adaptive optics 46 votes
Holography 47 votes
Laser eye surgery 53 votes
Optical storage media (CD/DVD/Blu-Ray) 60 votes
Laser…
drorzel | May 2, 2010With over 700 votes cast in the Laser Smackdown poll in honor of the 50th anniversary of the laser, laser cooling has opened a commanding 20-vote lead in the race to be the Most Amazing Laser Application of All Time. If you prefer one of the other options, you have only six hours left to change the final outcome:
Which of the following is the most amazing application of a laser?Market Research
Voting will remain open until midnight, with the ultimate winner announced on Monday, May 3rd. So get reading, and get voting. One vote per computer per user, please-- this is Serious Science.
drorzel | April 30, 2010We're just over 600 votes in the Laser Smackdown poll in honor of the 50th anniversary of the laser, as of early Friday morning. I notice that it has moved off the front page of the blog, though, so here's another signal-boosting repost, just so we have as many votes as possible, to establish maximum scientific validity when we declare the winner the Most Amazing Laser Application of All Time
Which of the following is the most amazing application of a laser?Market Research
Voting will remain open until next Sunday, May 2, just two days from now, with the ultimate winner announced on Monday…
drorzel | April 26, 2010As of 1:45 Monday, 217 people have cast votes in the Laser Smackdown poll. That's not bad, but it's currently being handily beaten by the 271 people who have voted for a favorite system of units.
The nice thing about using actual poll services for this sort of thing, though, is that I can re-post the poll to boost signal a little. So, here it is again, a list of the twelve most amazing laser applications suggested by my wise and worldly readers, with links to short explanations of the pros and cons of each:
Which of the following is the most amazing application of a laser?Market Research…
drorzel | April 23, 2010In 1960, the first working laser was demonstrated, and promptly dubbed "a solution looking for a problem." In the ensuing fifty years, lasers have found lots of problems to solve, but there has been no consensus about which of the many amazing applications of lasers is the most amazing.
Now, in 2010, as we celebrate the anniversary of the laser, we finally have the technology to definitively answer the question: radio-button polls on the Internet!
Which of the following is the most amazing application of a laser?Market Research
Each of the choices above links to a post I wrote here giving…
drorzel | April 21, 2010What's the application? An optical frequency comb is a short-duration pulsed laser whose output can be viewed as a regularly spaced series of different frequencies. If the pulses are short enough, this can span the entire visible spectrum, giving a "comb" of colored lines on a traditional spectrometer. This can be used for a wide variety of applications, from precision time standards to molecular spectroscopy to astronomy.
What problem(s) is it the solution to? 1) "How do I compare this optical frequency standard to a microwave frequency standard?" 2) "How do I calibrate my spectrometer well…
drorzel | April 13, 2010I'm teaching a junior/senior level elective this term on quantum mechanics. We're using Townsend's A Modern Approach to Quantum Mechanics, which starts with spin-1/2 and develops the whole theory in terms of state vectors and matrices. This is kind of an uneasy fit for me, as I'm very much a swashbuckling experimentalist, and not as comfortable with formal mathematics.
This occasionally leads to good things, though, such as Monday's class, on photon polarizations. the book uses some vector arithmetic to show that circularly polarized photons have spin angular momentum of one unit of h-bar.…
drorzel | April 12, 2010What's the application? LIGO stands for Laser Interferometer Graviitational Wave Observatory, because (astro)physicists feel free to drop inconvenient words when making up cute acronyms. This is an experiment to look for disturbances in space-time caused by massive objects, which would manifest as a slight stretching and compression of space itself.
What problem(s) is it the solution to? 1) "Can we directly observe the gravitational waves that are predicted by the equations of General Relativity?" 2) "Can we detect things like colliding black holes, because that would be awesome!"
How does it…
drorzel | April 12, 2010Several weeks ago, I announced a contest to determine the Most Amazing Laser Application. Personal issues interrupted this, but I want to finish it out in honor of LaserFest Here's the list of finalists, with links to those already written up:
Cat toy/ dog toy/ laser light show
Laser cooling/ BEC
Lunar laser ranging
Optical tweezers
Optical storage media (CD/DVD/Blu-Ray)
LIGO
Telecommunications
Holography
Laser ignited fusion
Laser eye surgery
Laser frequency comb/ spectroscopy
Laser guide stars/ adaptive optics
I'll be writing up LIGO shortly, and will try to finish the whole thing as soon…
drorzel | March 25, 2010I did one sketchy update from Portland last Tuesday, but never wrote up my impressions of the rest of the March Meeting-- when I got back, I was buried in grading, and then trying to put together Monday's presentation. And, for reasons that will become apparent, I was unable to write anything up before I left Portland
Anyway, for those who care, here are my impressions from the rest of the meeting:
Tuesday
In the 8am session, I went to the polymer physics prize talk by Michael Rubinstein, which was a sort of career retrospective, talking about how he wandered into the disreputable field of…
drorzel | March 24, 2010Several people have sent me links to news stories about last week's Nature paper, "Quantum ground state and single-phonon control of a mechanical resonator." (It was also presented at the March Meeting, but I didn't go to that session). This is billed as the first observation of quantum phenomena with a "macroscopic" or "naked eye visible" object.
Of course, there's a nice bit of irony in a story about quantum effects in a "naked eye visible" object that is accompanied by an image of the object in question taken with a scanning electron microscope. The longest dimension of the object in…
drorzel | March 15, 2010I'm terrible about taking notes on conference talks, especially when I'm jet-lagged and was sleep deprived even before I got on the plane. I do jot down the occasional paper reference, though, so here are the things I wrote down, and the talks they were associated with. This should give you some vague idea of what the meeting was like on Monday.
From Joel Moore's talk on topological insulators, one of the Hot New Topics in condensed matter, a review in Nature.
From Phillip Treutlein's talk on optomechanics, a recent preprint on coupling atoms to mechanical oscillators.
From Nathaniel Brahms'…
drorzel | February 25, 2010One of the weird-but-cool things about being C-list famous on the Internet is that some publishers now send me unsolicited review copies of forthcoming books about science. These aren't always the books I would really like to get free copies of, but, hey, free books.
Among the books I've received in the last year or so is Anil Ananthaswamy's The Edge of Physics, which I got as an ARC several months ago-- I read a bunch of it in Houston at the Sigma Xi meeting back in November-- but I just realized that it's due out next Tuesday, and I really ought to post a review of it.
As you can guess from…
drorzel | February 16, 2010Boskone this past weekend was held at the Westin Waterfront in Boston, which has these funky double showerheads that they charmingly call the "Heavenly(R) Shower" (hype aside, they are very nice showers). The picture at right is courtesy of lannalee on Twitter, as I didn't bring a camera.
Why am I telling you this? Because there was a sign glued to the wall in the shower that read:
Refresh yourself, restore our world
One of your Heavenly(R) Shower heads has been turned off in an effort to minimize water usage and protect one of our most precious natural resources.
The smarmy enviroweenieness…
drorzel | February 10, 2010What's the application? Using lasers to reduce the speed of a sample of atoms, thereby reducing their temperature to a tiny fraction of a degree above absolute zero.
What problem(s) is it the solution to? 1) "How can I make this sample of atoms move slowly enough to measure their properties very accurately?" 2) "How can I make this sample of atoms move slowly enough for their quantum wave-like character to become apparent?"
How does it work? I've written about laser cooling before, but the nickel version of the explanation is this: You can think of a beam of light as being made up of photons…
drorzel | February 2, 2010Congratulations to Alain Aspect, John Clauser, and Anton Zeilinger for winning the 2010 Wolf Prize in Phyiscs:
The 2010 Wolf Prize in Physics will be shared by Prof. John F. Clauser of the US; Prof. Alain Aspect of France's Ãcole Normale Supérieure de Cachan; and Prof. Anton Zeilinger of the University of Vienna. The jury in this field praised them "for their fundamental conceptual and experimental contributions to the foundations of quantum physics, specifically an increasingly sophisticated series of tests of Bell's inequalities, or extensions thereof, using entangled quantum states."
All…
drorzel | January 26, 2010Way back in the early days of ScienceBlogs, I ran a competition of sorts to determine the greatest physics experiment in history. I collected a bunch of nominations, wrote up a post about each of the top 11 entries, and then asked people to vote for their favorite.
In honor of the 50th anniversary of the laser, let's take a stab at something similar:
What is the coolest thing you know of that's done with lasers?
Lasers are all over the place these days, from UPC scanners to telecom networks to optical drives to hospitals. All sorts of fascinating things have been done with lasers over the…
drorzel | January 25, 2010As mentioned previously, I've been reading Sean Carroll's Wheel arrow of time book, which necessarily includes a good bit of discussion of "Maxwell's Demon," a thought experiment famously proposed by James Clerk Maxwell as something that would allow you to cool a gas without obviously increasing entropy. The "demon" mans a trapdoor between a sample of gas and an initially empty space, and allows only slow-moving gas atoms to pass through. After some time, the empty volume is filled with a gas at lower temperature than the initial sample, while the gas in the original volume is hotter than…