Faster than light
This is a touchy topic for a lot of people, so I hesitated for a few days to post it. I'll keep the quoted text to a minimum, so you'll need to do extra clicking to go outside this blog if you want to read it all. I'm sorry for being such a windbag on this topic. There's a fun thought experiment at the end for any of you who make it that far.
A team of French researchers managed today both to speed up and slow down light. Normally light travels about 300 million meters per second, but the team was able to slow it down by a factor of 3.6, or make it travel slightly faster. The researchers say slowing down light will help signal processing, allowing us to vastly speed up telecommunications.
Source: Technocrat
So what's the big deal? As one commenter said regarding the faster than light claim, "I call bullshit." For the sake of the average person's understanding of the matter, that comment is right on the money. Can we travel faster than light (without using some so far unattained "tricks" used in common science fiction stories)? No. Specifically, information cannot travel faster than light. Arguably, photons themselves might be convinced to go faster than light... but not convey any information.
Keep in mind that the claim of slowing light down is not a big deal. The "speed of light" commonly references is that of light traveling through a vacuum. Light goes slower through any other matter, such as water, glass, air, etc.
Cerenkov radiation is an interesting example of charged particles going faster than the speed of light in water (0.75 c). The result is a blue glow around the submerged reactor. The photo to the right is an image of the nuclear reactor at PSU. At night on campus you can pick NucE students out of a crowd by their faint blue glow. ... just kidding.
So how did they get a result that showed faster than light (c) velocities? I'm not fully qualified to explain it, so I'll give a few references. The key to it is the difference between light's group velocity and phase velocity. Commenters (1, 2) to the Slashdot article give a little insight into the difference. This page has a really good animated graphic to help you understand the illusion of faster-than-light information transfer.
This Science Blog article on this gives a good explanation of why changing light's velocity is important to the future of communications. This MSNBC article covers a similar story back in 2000.
Now if you've made it this far through this blog entry, I'll give you a prize and mix in my own personality to yield another interesting explanation for faster-than-light photons. (Disclaimer: at this point, this is more fiction than science.) To simplify the question, how can a photon leave a box at the same time it enters a box? I like to apply a many-worlds interpretation to it. This interpretation usually doesn't get used in this situation, but more so for the double-slit physics experiment. You might remember it from science class. When using multiple photons, it shows that light behaves as a wave rather than a particle. When using a single photon, the end result of the experiment is the single photon producing an interference pattern on the screen, which seems impossible (a second photon is required to create an interference pattern in their waves). The many-worlds interpretation postulates that the second photon is from a parallel universe where the photon went through the other slit. Up to that point the universes were identical, but they split upon this experiment to yield the observed interference pattern. (This requires some quantum effects to coexist between the universes after they split. This may be a form of quantum entanglement in a spatial dimension across multiple universes.) I propose that universes can also split based on temporal offset decisions (when the photon starts it travel through the box... ultimately when it exits) and not just spatial offsets (which slit the photon goes through).
You can easily prove the existence of multiple universes if you want. All you have to do is commit quantum suicide. Automatically kill yourself based on the decay of a single radioactive particle. This is just like the Schrödinger's Cat experiment, except you are the cat. How does it work? There's a 50% chance you live, 50% chance you die. If it is a splitting point for the many-worlds interpretation, in one universe you live, and in the other you die. In the one you die... well, you die. But in the other you live. Repeat the experiment. After you have repeated it sufficiently, it would be so extremely statistically improbable for you to have survived so many random 50/50 chances that you can take it as evidence of the many-worlds interpretation. Of course, for every time you did the experiment, you're dead in another universe. But why care? You're alive in this one, and you know that the many-worlds interpretation is correct. The extention of this experiment is the idea of quantum immortality. Enjoy!
Comments
Everyone keeps talking about Quantum Entanglement like it's something people should just know. So I spent a few years writing up a site that explains how QE works, without math, but with plenty of pictures and analogies.
Quantum Entanglement
Posted by: Dave | October 7, 2005 09:06 PM