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The Casimir Force
Just walked by the poster about the Casimir Force in the third floor hallway and decided I felt like explaining it to the random assortment of people who read my blog.
Okay, one of the many nifty things about the Casimir Force is that it's proof that Heisenberg's Indeterminacy Principle isn't just a mathematical cop-out.
In a nutshell, the Casimir Force is a force of attraction between things that get microscopically close. But it's actually a pushing force, not a pulling force. I will explain (and leave out a lot of details that might irk any physicists reading this).
Premise 1: One of the many results to drop out of the Heisenberg Indeterminacy Principle (Uncertainty is the common English translation, but Heisenberg himself preferred Indeterminacy) is that vacuum isn't completely empty. Rather, it's full of virtual particles that appear and disappear at random. The higher the energy, the less time the particle exists, so you mostly get photons (light) rather than baryons (protons, neutrons, that sort of thing), since they can be lower energy.
Premise 2: All particles or waves that impact something exert force on it. This one shouldn't require much explanation.
Premise 3: All particles have a wavelength, including virtual ones. This is something that a guy named deBroglie worked out.
Premise 4: If you have a cavity of some sort, that's "closed" at both ends, then only stuff with a wavelength such that the size of the cavity is an even multiple of half the wavelength will be able to exist in the cavity. Any other wavelength will bounce back and forth and cancel itself out in very little time.
Putting it all together: Put two plates really close to each other, like nanometers apart. Any wavelength greater than twice the plate separation can't exist between the two plates (well, at least, not in the direction pointing between plates...they can still skim along parallel to the plates). So as the plates come together, more and more virtual particles simply cannot come into existence that otherwise would have.
Meanwhile, outside the plates, the usual bestiary of particles is still merrily popping in and out of existence. These particles exert more force on the outside of the plates than the ones between the plates can exert on the insides of the plates. In cruddy ASCII, this looks like:
MORE FORCE | less force | MORE FORCE
MORE FORCE | less force | MORE FORCE
MORE FORCE | less force | MORE FORCE
This results in the plates being pushed together by the force of virtual particles. Going back to my initial statement about Indeterminacy, this is a nice experimental proof. The Casimir Force means there's virtual particles. Virtual particles mean there's Indeterminacy. (Vastly simplified, of course, and leaving out all the various loopholes that may or may not have been plugged.)
Of course, this is all at the atomic and sub-atomic scale, and we probably won't see it used for hovercars or spaceships or whatever. But it's still kinda nifty.
Okay, one of the many nifty things about the Casimir Force is that it's proof that Heisenberg's Indeterminacy Principle isn't just a mathematical cop-out.
In a nutshell, the Casimir Force is a force of attraction between things that get microscopically close. But it's actually a pushing force, not a pulling force. I will explain (and leave out a lot of details that might irk any physicists reading this).
Premise 1: One of the many results to drop out of the Heisenberg Indeterminacy Principle (Uncertainty is the common English translation, but Heisenberg himself preferred Indeterminacy) is that vacuum isn't completely empty. Rather, it's full of virtual particles that appear and disappear at random. The higher the energy, the less time the particle exists, so you mostly get photons (light) rather than baryons (protons, neutrons, that sort of thing), since they can be lower energy.
Premise 2: All particles or waves that impact something exert force on it. This one shouldn't require much explanation.
Premise 3: All particles have a wavelength, including virtual ones. This is something that a guy named deBroglie worked out.
Premise 4: If you have a cavity of some sort, that's "closed" at both ends, then only stuff with a wavelength such that the size of the cavity is an even multiple of half the wavelength will be able to exist in the cavity. Any other wavelength will bounce back and forth and cancel itself out in very little time.
Putting it all together: Put two plates really close to each other, like nanometers apart. Any wavelength greater than twice the plate separation can't exist between the two plates (well, at least, not in the direction pointing between plates...they can still skim along parallel to the plates). So as the plates come together, more and more virtual particles simply cannot come into existence that otherwise would have.
Meanwhile, outside the plates, the usual bestiary of particles is still merrily popping in and out of existence. These particles exert more force on the outside of the plates than the ones between the plates can exert on the insides of the plates. In cruddy ASCII, this looks like:
MORE FORCE | less force | MORE FORCE
MORE FORCE | less force | MORE FORCE
MORE FORCE | less force | MORE FORCE
This results in the plates being pushed together by the force of virtual particles. Going back to my initial statement about Indeterminacy, this is a nice experimental proof. The Casimir Force means there's virtual particles. Virtual particles mean there's Indeterminacy. (Vastly simplified, of course, and leaving out all the various loopholes that may or may not have been plugged.)
Of course, this is all at the atomic and sub-atomic scale, and we probably won't see it used for hovercars or spaceships or whatever. But it's still kinda nifty.