Casimir Effect

This entry is going to be on a fascinating quantum physics effect, that until recently was just theory. There’s some intense physics going on here, but I’m going to do my best to keep you guys along (I’m not all that great with quantum mechanics either, so don’t worry if you find this stuff a little intimidating—we all have trouble grappling with this stuff. But it’s totally worth it when you realize how awesome it is). I write this entry in honor of being sent this article: http://www.nature.com/news/2011/110603/full/news.2011.346.html

A quick refresher for all of you: quantum mechanics is the study of the microscopic world, which to a physicist, means things like atoms and individual particles. The world of particles is really crazy; things become governed not necessarily by what we observe, but by the probability of what we could observe. However, for this entry, this isn’t all that important to remember. Instead, there is one effect of quantum theory that you DO need to keep in mind. Physicists believe that empty space, or a vacuum, is actually not completely empty. Instead, there are numerous particles, called virtual particles, that can pop in and out of existence on extremely small time scales. These virtual particles always exist in a pair, one being the “normal” particle and the other being an “antiparticle”, which are identical in size but opposite in charge. These then come together so fast and annihilate each other that they can barely even be said to exist. Pretty crazy, huh?

The Casimir effect is something that takes advantage of this idea, but in a fascinating way. Take two mirrors and place them very close together in a vacuum. The concept is that if these mirrors are close enough together, only so many virtual particles (e.g. virtual photons, or particles of light) can exist between the two mirrors. Then, since there are more particles on the outside of the mirrors than there are on the inside, you end up with a force that pushes the mirrors together. This force is called the Casimir Force, and it is a way for scientists to prove the existence of these virtual photons.

In the experiment mentioned in the article, the scientists were looking for something very similar to this. The theory states that if you have a single mirror plate, moving very fast, you can essentially absorb the energy in the virtual photons with the plates surface, and then re-emit them as real photons! Remember that in physics, particles such as those that make up the mirror’s surface can absorb photons and get “excited”. After some time (often a very short time), the particles on the surface will emit the same photon away, and stop being in the “excited” state. So the idea is the same here, except instead it is absorbing the virtual photons instead of “real” ones, and then when the mirror re-emits it, it doesn’t annihilate with an anti-photon, and so it becomes what we call a real photon. So to an observer, it will appear like the mirror has created light out of nothing!

The scientists used a super-conducting circuit that acted essentially like a mirror, and were able to wiggle it at roughly 5% the speed of light, using a magnetic field. This effectively created the effect to occur; out of a particle “vacuum”, they produced microwave photons!

The application for this is not very clear, but it is still a fascinating result. A lot of the physics predicted by quantum mechanics always seems weird and not intuitive, and yet all over the place we see more and more evidence for it to be fact. And so, yet another interesting theory proven in the laboratory. If you are a lot more scientifically literate than most, you can read the scientific paper released on the site I mentioned above. If you have any questions or comments, please leave them! Until next time.