I felt it was about time for another installment of a new favorite series here at Sci-ence.org. The laser is a wondrous thing, and scientists who play with them have bestowed upon me material for years to come. Let’s take a look at what they’re doing this time.
Seeing Sound: This is a fascinating use. The folks at NPL shine a laser at a retro-reflective board (meaning it shines back at the source) and measure the time it takes. Add a speaker to the mix, and they can visualize the sound waves based on the travel time of the laser. Pretty nifty! They expect this should provide manufacturers with an easier, more accurate way to fine tune their speakers.
Laser Cooling: This is a pretty weighty one, I hope I both explained it correctly and concisely. Utilizing the Doppler effect and a bunch of lasers, scientists can cool a gas down to near absolute zero. Temperature can be described as the amount of kinetic energy in a medium. The more the atoms move around, the hotter they are. What happens is that the lasers are tuned to such a low frequency that they pass through the gas without hitting anything. But if an atom approaches the laser beam head on and at the right speed, the Doppler effect causes the laser frequency to increase in relation to the moving atom. A photon hits the atom, gets absorbed, and then re-emitted. The result is a net lost of velocity for the atom. This is done over and over again, and the lasers tuned lower and lower until the atoms are nearly motionless. Recently, the folks at Caltech were able to do this with a small object.
Deuterium: In the infant universe, there existed only a hot, dense soup of hydrogen, helium, and deuterium (which is hydrogen with a neutron tacked on). This cloud, over time, collected and became the first stars. When those stars died, they seeded the universe with more stars and heavy elements. At the National Ignition Facility, scientists are firing high powered lasers at deuterium pellets (more desirable than hydrogen because of that neutron) in an effort to start a fusion reaction. Fusion needs a high amount of energy to kick-start because you’re trying to overcome the electrostatic force. The lasers super-heat the deuterium, making it contract to the point where the nuclear force takes over, and the atoms fuse, releasing huge amounts of energy.
Flow Cytometry: Pretty simple, cells are funneled past a laser beam and the scattered light is analyzed to both identify what is being hit and how many there are.
Biological Laser: Recently, a human kidney cell was engineered to produce a phosphorescent jellyfish protein. When exposed to blue light, the cells gave off a green glow. When placed between two tiny mirrors, the cell made a green laser that didn’t kill the cell. Until now, non-biological “gain mediums” were used, such as crystals, semiconductors, or gases.
One thing I found that I didn’t have room for was the use of a confocal scanning laser microscope to create these amazing 3d images of insects. The CSLM works by shining a laser onto the subject and recording the reflection while simultaneously splitting the beam into a reference collector. After that, various filters are used to remove out of focus light and the original laser beam. The advantage of CSLM is that you can take high-res images at various depths, which is how it creates such sharp, topographical images. Cool stuff!
This post was brought to you by Laser Cooling.
Thanks to all of those who shared Monday’s Red Flags of Quackery update! I saw every mention and retweet and it was an honor to see some of my heroes of the science journalism world share the piece, including Bora Zivkovic, Kevin Zelnio, Ed Yong, and Sheril Kirshenbaum. Also thanks to David Brin, K.O. Meyers, Brad Goodspeed, and Scicurious. As we speak, the Red Flags are being translated into Spanish and Turkish, I’ll be posting a more kid-friendly version soon, and after that a buy-able poster over at our Zazzle store.