Scale Models Can "Compute" Casimir Forces 136
KentuckyFC writes "Place two conducting parallel plates a few nanometres apart and the well-known but difficult-to-measure Casimir force will push them together. The force depends crucially on the shape of the plates but nobody is exactly sure how. That's because calculations with anything other than flat plates are fiendishly difficult and measurements are even harder. Now a group at MIT has come up with an ingenious new way to investigate Casimir forces. What the team has noticed is a mathematical analogy between the Casimir force acting on microscopic bodies in a vacuum and the electromagnetic behavior of macroscopic bodies floating in a conducting fluid. Their idea is to build a centimeter-scale metal model of the system they want to investigate, place it in salt water, and bombard it with microwaves and see what happens. The team says the experiment does not measure the force on the scale model but instead a quantity that is mathematically related to the force. So the experiment is not a simulator but actually an analog computer that calculates the force (abstract). What's exciting is that the method should for the first time give researchers a way of testing nano-machines designed to exploit the Casimir force."
Casimir Force (Score:3, Interesting)
Could someone provide a comprehensible description for non-physicists of what the Casimir Force is? I looked it up on Wikipedia (and like all math and physics related articles there) came up with a borderline unintelligible "summary".
It's overview is:
It's intro is similar:
Re:Is this really the scientific method at work? (Score:4, Interesting)
Re:A computer? (Score:3, Interesting)
I don't have a problem with that definition. But it also means 'quantum computers' shouldn't be called 'computers' either.
Re:Casimir Force (Score:5, Interesting)
Good explanation.
An oft-used classical analogy is of boats on a wavy sea. It's been reported that two ships sitting on a wavy sea (but windless day) will slowly move closer together, as if they are 'attracted' to one another. The origin of the force is the waves of various wavelengths that form on the water surface. The sea surface has waves of all different sizes. In between the two ships, however, some wavelengths can't 'fit' and so those modes are suppressed. The end result is that there are fewer wave between the ships, so the greater pressure from the (more) waves on the other sides of the ships pushes them closer together. (I'm glossing over the details, e.g. that you have to take into account how the waves on the surface of the sea reflect off the ship's hulls... but hopefully you get the idea.)
The Casimir force is like the quantum version of this. According to quantum mechanics, the vacuum is constantly churning with the creation and annihilation of virtual particles. Thus there are quantum waves of all kinds of different wavelengths. In between two plates, some quantized modes can't exist, and are suppressed. The end result is that there is more pressure from the vacuum on the outside of the plates than in the gap between them. Hence the plates are pushed together by the vacuum pressure.
Note that in both cases the magnitude of the force is quite small, and so you have to be quite careful to observe the force and measure it properly.
Eureka! (Score:5, Interesting)
Also I didn't see the meme so I have to do this,
But will it run Linux?
Question: Uncertainty Principle (Score:3, Interesting)
Years ago, I read "A Brief History of Time" and Stephen Hawking asserts that the reason that Particles randomly pop into existence and annihilate again is because of the uncertainty principle. You can never know the exact momentum and position of a particle with complete certainty, and the more you know of one, the less you know of the other. Then, he says, you can never have a true vacuum. The position and momentum of this "vacuum" would _both_ be zero and since that simply can't be, there must be fluctuations.
WTF??!?!
I've read the passage over and over again, and I swear that _that_ is his line of reasoning, but it makes NO sense to me. I thought that the uncertainty principle was all about measurements, and altering things whenever you try and look at it... not about whether some random hypothetical area of space can exist as a vacuum or not.
Am I missing something, or did Stephen Hawking take some particularly potent Valium that day?
Re:Casimir Force (Score:3, Interesting)
Time an again it has been shown there is no free energy no matter how you slice it. We had our peak during the big bang, and its all been going down hill since then. The most we can hope for is to harness as much of the already existing energy as we can.