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British Scientists Reverse Casimir Effect
An anonymous reader writes "The Telegraph reports that Scientists at the University of St. Andrews have developed a technique to cause the Casimir effect to repel instead of attract. This discovery could lead to near frictionless machines or in theory even levitation."
It's "repel" as in "the body odor of submitter repels women worldwide", as opposed (heh) to repeal, which means, "to remove or reverse a law".
The BBC are slightly more useful at http://news.bbc.co.uk/1/hi/scotland/edinburgh_and_ east/6932283.stm - they say it's a "friction reducing lens". Still doesn't give us a lot to go on, but it's a start!
The discovery is not to be belittled, but both the article and the poster somehow forget to mention that the "levitation" which is talked about is on the order of nanometers (check the Wikipedia article on the Casimir effect). Far from the kinds of stuff you see stage magicians do.
"Goodness me, how unlike the FBI to abuse the trust of the American public." -- The Onion
Now, Leonhardt and Philbin have calculated that the Casimir force between two conducting plates can turn from being attractive to repulsive if a "perfect" lens is sandwiched between them. A perfect lens can focus an image with a resolution that is not restricted by the wavelength of light. Such a lens could be made from a metamaterial made of artificial structures that are engineered to have negative index of refraction -- which means that the metamaterial bends light in the opposite direction to an ordinary material.
According to the researchers, the negative-index metamaterial is able to modify the zero-point oscillations in the gap between the surfaces, reversing the direction of the Casimir force. Indeed, the researchers believe that this repulsive force is strong enough to levitate an aluminium mirror that is 500nm thick, causing it to hover above a perfect lens placed over a conducting plate. Since the Casimir force acts on the length scale of nanomachines, manipulating it could be important for future applications of nanotechnology. To summarize, nothing has been built yet. It's possible that it could be built, though you'd have to make a "perfect" lens in the tiny space between the two plates. Unfortunately, every "perfect" lens I've heard of tends to be wavelength-specific and relatively large (compared to the gap the Casimir effect requires). It may be that these are just engineering hurdles, but it may also be physically impossible to pull off.
the Frictionless lens is a material with negative refractive index... ...err ...kinda
which seems to change the energy distribution of the vacuum
i didn't post the page of the author for obvious reasons, suffice it to say the profs do have a page with a nice laymen explanation(well laymen 'cause theres no math)...google is your friend
Try checking out the University website - it had much more information about the science of the discovery:
http://www.st-andrews.ac.uk/~ulf/levitation.html
Pity they have a photo of Syndrome and his Zero-Point Energy device as an example at the top. Doesn't help anyone to take them seriously surely.
Quantum levitation by left-handed metamaterials
Ulf Leonhardt and Thomas Philbin
Provisionally scheduled for August 2007
Thanks for the link - the Wikipedia article explains the effect and says that for materials with certain electromagnetic properties and configurations, the Casimir effect might result in a repulsive force instead of an attractive. Looks like somebody demonstrated that. Still, there's a long way from this to a macroscopic levitation system...
A humorous page about these British scientists' work by St Andrews physics Professor Leonhardt explains their work on Casimir "levitation".
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make install -not war
This wasn't enough for me, so I wandered over to Wikipedia:
The only changes to the Wikipedia article lately have been a link to this article, which is sort of meta. Wikipedia linking to an article plagiarizing from, of all places, Wikipedia. Cute, but also a little sad.
Against stupidity the Gods themselves contend in vain.
I have a masters in physics, and although im not an expert in these things, i believe i have a better working knowledge than parent.
:-) .
In the quantum description of the electromagnetic field, there is no such thing as uniformly zero field - even in completely empty space, there are oscilations in the field spread over all modes (ie. wavelengths). It can be compared to an ocean or pond in stormy weather where there will allways be *some* waves.
Now, if we have a geometry consisting of two flat opposing plates, only certain wavelengths corresponding to the distance between the plates will be allowed. Thus by increasing or decreasing the distance between the plates, we can deside which zero-point wavelengths will be allowed, and it is such that the situation where the plates are very close are energetically favorable, hence we will see the two plates attract each other and this is known as the casimir force which has been measured many times in the experiment. Its important to realize that its not charges on the plates which are doing the work - everything is kept charge neutral. Its vacuum doing work
(by manipulating the geometry of the plates, inserting lences, etc. its then theoretically possible to make the plates repel instead, which is what the article is about)
Anyway. My point is. This is not like nuclear chain reactions. The experimental conditions under which you see these effects are extreme (as in: the truck on the street or the cellphone in the assistants pocket will ruin it). Its a neat discovery, but the doom and gloom is completely uncalled for.
Because not many people will understand the reference:
http://en.wikipedia.org/wiki/Uplift_Universe
http://www.mhall119.com
I believe the answer is U.S. Patent Number 1 by Cheapass Games.
/-\-/
The Casimir effect is very wierd indeed. If you take two metal plates and put them close together in a vacuum they will attract one another VERY weakly. The effect is caused by fluctuations in the electric charge of the vacuum. Think of it a little like sea level. On average if you measure sea level lots of times you wil get "0" for the height but if you measure it just once the height you get will depend on the tide and the size of any waves. The same is true for a vacuum. Look at a particular volume of space and measure the electric charge. On average you will get zero but for a particular moment in time it may be non-zero.
Ok so far but how do we get an attractive force? Well it turns out that charge must be conserved so if one region of space has a small positive charge at one instant a neighbouring area must have a small negative charge (in quantum terms we say that we pair produce and virtual electron-positron pair) thuse we have a dipole. Now remember the two conductors? Well the one nearest the positive charge will have the electrons in the conductor attracted to it and being a conductor they will move towards it giving the conductor a net negative charge. The opposite will happen in the conductor nearest the negative charged area of space.
So now we have, instantaneously, a conductor with a negative charge and one with a positive charge...so they attract one another. this is the Casimir effect. If you stop to think about it is is VERY strange because it means that two metal plates in vacuum, with no externally applied fields will attract...so you have to ask yourself what exactly is doing the work i.e. where is the energy coming from to move these plates?
I'm not a condensed matter guy so I must admit I don't quite understand why this effect is so important to them. I understood that in molecules it was known as Van der Waal forces and due to periodic dipoles occuring in molecules in much the same way it does ina vacuum. Only, because there is a real electric field, the effect is much larger. So if there are any condensed matter people out there perhaps they would like to explain why it is Casimir and not Van der Waals that is important? or is it just because they have the same origin the name Van Der Waals has been dropped?
The energy isn't created really, is kept from moving into the area between the plates.
Let me explain further:
Heisenberg's uncertainty principle says you can't know where a particle is, or it's momentum, at the same time. That applies to space too. For any point in space, you can't know if there's a particle there or not.
Therefore, the reality is that the vacuum is boiling all the time with particles popping into and out of existence all the time. Particle soup. For another interesting effect of this, check out Hawking radiation.
Anyway, if the plates are close enough together, no particles can be popping into existence in that space, because it's too small. It's literally small enough that if there were a particle there, you'd know it's position and momentum, and that is NOT allowed.
So, the situation you've set up is that you have two plates very close together, with particles appearing and disappearing on one side of the plates (the outside surfaces) but not on the inside surfaces. That means that there's a pressure created which forces the plates together.
No energy is created because what you're doing is preventing particles (energy) from appearing inside the plates. The energy of a vacuum is not zero because of those particles. The energy inside the plates is zero (zero point energy).
The problem is that once the plates have moved together which is work, you don't get any more work out of the system unless you move the plates back apart.
No weapon in the arsenals of the world is so formidable as the will and moral courage of free men.-Ronald Reagan
Here's the paper, courtesy of arXiv:
http://www.arxiv.org/abs/quant-ph/0608115
It should be noted that this work is purely theoretical. What they have done is show that there is a much more physically realizable way to way a repulsive Casimir effect than the previous schemes, using a material with negative refraction over some range of important frequencies (this is a similar problem as making a cloaking device, but with a harder range of the spectrum). In practice, the effect would be small and the material hard to make, but the idea is interesting.
The universe has three sections: the part between the plates, the part to the left of the left plate, and the part to the right of the right plate. All three parts of the universe are undergoing adiabatic expansion and are thus applying pressure to their boundaries. Generally they have more success at the edges of the universe (near where the CMB appears) than at the surfaces of the plates since it isn't clear that they have anything to push against near the CMB, but the boundary conditions at the surface of a plate are different because of the universe on the other side. The universe in the middle of the plates doesn't do a good job of expanding because even virtual particles have trouble fitting in there (the plates form a high pass filter that attenuates any long wavelength standing waves), so the other two parts of the universe make it contract. Soon the virtual particles in the middle universe have very high energy and apply an imaginary pressure on the plates that counters the imaginary pressure being applied from the two external portions of the universe, and this affects the position of the plates relative to one another. The force can either be attractive or repulsive depending on the electromagnetic characteristics of the plates and their effects on the wave functions of the charged virtual particles inside.