Bose-Einstein condensate is normal material, but under extreme circumstances, at least as far as are current environment is concerned. I have no idea if this techonology will ever trickle down to our every day lives, but it sounds interesting enough as it is. Who knows, we’re only a million million times off right now. Although your slow glass will likely be inferior to the state of the art recording device, I guess it’ll be a fun toy for your kids at least. Just be careful where you put that darn thing 
Actually, I would say the Bose-Einstein condensates are not normal matter if we can define normal matter as being atoms in one of the usual states: solid, liquid, gas or plasma.
A BEC is a weird sort of matter where atoms lose their individual identity and coalesce into a single object. Basically you end up with a single atom, large enough to be visible to the naked eye.
Here’s a blurb from Scientific American on the subject:
[QUOTE]
Albert Einstein and Satyendra Nath Bose predicted more than 70 years ago thatjust above absolute zero, quantum mechanics could make atoms in a group indistinguishable they would merge into a single gigantic atom. In 1995 this new form of matter was created at last…[/QUOTE
I think it’s clear that BECs don’t occur naturally, and that this would exclude them from being classified as normal matter.
Of course, we could just have different definitions of normal.
gEEk
Dang! For the want of a ] my quote was lost.
gEEk
Common material would have been a better choice of words. Unless Bose-Einstein condensate has become common. I hear it’s great for keeping drinks cold.
I prefer liquid nitrogen for that…
It’s always fun to toss a can of coke into a bucket of liquid nitrogen. Bose-Einstein condensate is just too much of a hassle. Not only will you kill the bubbles in your soft drink, you’ll also have to spend the next month replacing your vacuum pumps
Arjuna34 wrote:
I don’t know about on the web. From what I recall, water doesn’t start conducting for seven to ten microseconds, so if you don’t have the capacitors charged up for longer than that, they’re pretty ideal.
How much above absolute zero to get a BEC? Isn’t the average temp of space something like only 3 degrees?
Fromt eh article listed above "Vacuums hundreds of trillions of times lower than the pressure of air at Earth’s surface, and temperatures almost a billion times colder that that in interstellar space, are needed to produce the condensate. Temperatures must be lowered to within a few billionths of a degree of absolute zero (minus 459.7 degrees F), where atoms have the least possible energy and all but cease to move around. "
So there is the answer to my previous reply.
Refractive indices for those of you who were unaware:
Silicon: 3.42
Germanium: 4.0
Gallium Arsenide: 3.6
(I believe these are in the IR-ish range. Si for sure.)
Thanks for the great response to my questions. I realized at the time that I was hijacking howardisms’ thread, but I thought that Zor had answered it pretty well. Hope you don’t mind, howie!
Thanks especially to gEEk for that great link! I wondered whether such a thing might be possible in a laboratory, but I never thought it would already have been created. I wonder what the density of the E-B condensate is. I would love to read more about it. Really glad you decided to step out of the shadows and join the conversation, gEEk. Welcome aboard!
Also to Spiny and Finagle for tracking down that story. I definitely remember it beeing a somewhat depressing, but beutifully poetic, “mood” piece. I think it may even have been the one you mentioned. Ever since I heard part of it on the radio something like ten years ago, I’ve wanted to find it. Thanks a lot!
Oh, yeah, gEEk, the link you posted referred to an article in Nature, but your quote was from Scientific American. What issue did you find that in, so I can read it myself?
I don’t think howardsims’ original question has yet been answered, although NanoByte made a valiant effort with his sand-sifting analogy. Zor’s original statement (light is an EM wave that interacts with matter) is correct, but doesn’t really answer the question. The question intrigues because it arises out of the difficulty of analyzing quantum phenomena armed with classical intuition.
The simple answer to the question is that the photons do move between the atoms at the speed of light in vacuum ©, but as they pass by atoms they are absorbed and then reemitted. The absorption and reemission process takes time, so the rate of travel through the material is slower than c. The problem with this view is that atoms aren’t little well-defined specks with space between them, and photons aren’t little well-defined specks that jump from atom to atom at the speed of light. An atom is of indefinite size once you start trying to pin it down to less than the uncertainty in the positions of the electrons–something on the order of an Angstrom or so. Similarly, the idea of the “size of a photon” is meaningless at less than a few wavelengths–something on the oreder of a few thousand Angstroms. So if you insist on thinking of atoms as particles and photons as particles, the photons are much bigger than the atoms or the spaces between them.
If you want to be rigorous in thinking about the process of propagation of light through a material medium, you have to keep in mind that the photon is the quantum of energy of interaction between the light and the matter, not a microscopic billard ball (or grain of sand in NanoByte’s analogy). As the light propagates through the matter, the light gives up energy to the matter in increments of the energy of the photon (E=hf where h is Planck’s constant and f is the frequency of the light wave). The photon doesn’t “lose momentum” in collisions with the atoms, it disappears entirely. But photons don’t really exist while they are traveling; they only exist as a way of describing the interaction with matter. Confusing? Anybody who says QM is easy is a liar or doesn’t understand it. (Einstein got the Nobel prize for stating the bit about E=hf; a dozen others have been awarded to people for arguing about what the rest means.)
So anyway, as this conglomerate of “photons” impinges on this conglomerate of “atoms”, the light energy is absorbed (by changing the relationships of nuclei and electrons), but that atoms don’t retain the energy so they reemit it as new light energy, but that gets absorbed again, and so forth. You might as well think of it just as if the light were some kind of wave that propagates through the material. But that, of course, is exactly the classical electromagnetic view. Light is the propagation of electromagnetic waves through a material medium. The speed of propagation may be accurately computed from purely classical principles as 1/sqrt(permittivity*permeablilty). You can compute the speed of sound in exactly the same way using the density and compressibility of the medium instead of the permeability and permittivity.
Now, you ask, if EM waves and sound waves are analogous, what’s the sonic analogy of a photon? It’s called a “phonon.” Which brings us to Bose-Einstein condensation.
Photons are interesting entities in that they are indistinguishable. Think about it: you can’t paint a serial number on the side of a photon. Heck, it isn’t really a thing. Swap two photons and who’s the wiser? They also have the peculiar property that two of them can occupy the same quantum state simultaneously. The result is that light beams are interpenetrating without interfering with each other. Matter isn’t typically like this. The culprits are electrons, which, although indistinguishable, can’t share the same quantum state. Good thing, too, or matter wouldn’t be very substantial.
Physicists call photons (and their ilk) “bosons,” after SN Bose; and they call electrons (and their ilk) “fermions” after E Fermi. Are there any material bosons? Well, yes. Helium-4 atoms are bosons. Normally helium is pretty normal stuff, but if you get it cold enough (below about 1.2 K --not hard to do at all) many of the atoms want to be in their energy ground state, and because they are bosons, they can all enter the same state. Talk about indistinguishable! They not only look alike, they are all in the same place doing the same thing at the same time. They are all the same thing.
The idea that the Bose-Einstein Condensate is new is poppycock. Heck, I made the stuff routinely in the seventies. People have been doing it since the teens, and understanding it since the fifties. It’s even made its way into technology. Electrons are fermions and therefore can’t form a Bose-Einstein condensate at any temperature. But pairs of electrons are bosons, and can form a BEC. (The reason is that integral spin particles are bosons, and half-odd integral spin particles are fermions. Two half-spin electrons makes a whole-spin or zero-spin pair. Dont’ ask.)
The trick is to get the electrons–which electrically repel each other like mad–to form a pair. Phonons to the rescue. In certain solids (originally frozen Mercury) the interaction of phonons and electrons as sound waves propagate through the material causes a bizarre interaction of the electrons so they form pairs known as Cooper Pairs. A Cooper Pair is a boson; it can form a BEC. A material that does this is called a superconductor. Superconductors are old hat.
Me thinks Geezer just slaughtered the popular science crowd
Anyway, if you really want to get into the details, you’re in for a long haul. I believe Bose-Einstein condensates were made popular just a few years ago when someone hit the jack pot and won a Nobel Prize for developing more efficient techniques of manipulating it (feel free to correct me, I’m in a lazy mode now).
Also, I should’ve made the disclaimer that most material have a refractive index less than 3, so long as we’re considering visible wavelengths. Didn’t expect you guys to really dig up the numbers so I just let that slipped 
I must confess I’m surprised Germanium is transparent though. What’s the story on that? I thought most of the solid elements were not transparent?
Hey Geezer,
You need to straighten these people out, they seem to think they created the first condensate in '95.
http://jilawww.colorado.edu/bec/
By sheer coincidence, I was visiting UW when those guys had their fifteen minutes of fame, and one of them was the colloquium speaker in the Physics Dept. He gave a great talk, reporting on really wonderful work. Their method was ingenious: contain a gas of hot rubidium atoms in a laser trap; cool the whole thing down until the condensate forms; then release the trap so the non-participating atoms blow away; and, voila–a pure BEC! I wouldn’t call it the first BEC, but it’s still a fabulous experiment, and historic.
You can make an analogy between Bose condensation and freezing. When you cool a bose gas, instead of condensing to form a solid, the bosons condense into the momentum ground state. Using this analogy, what we used to do with helium was like making slush in a dark room and saying we must have made ice because the stuff maintains its temperature while you add heat and the stirring rod feels “slushy.” By comparison, these guys made an ice cube, fished it out or the water, and made a video of it melting.
As for the claim that the BEC does not occur in nature: the material of a neutron star is a superfluid. It contains a Bose condensate of the neutrons (which are bosons).
It’s a sad thing that scientists have to play for the cameras nowadays. The current hoopla about the Moon Illusion is a good example. The moon illusion has been explained since the fifteenth century. Irwin Rock had it worked out in modern terms in the sixties, but some people just didn’t believe him. Now IBM gets in on the act and it’s a done deal. Notice how all the news articles talk about the use of a ThinkPad? Not a computer, not a laptop, a ThinkPad.
The extreme case is Pons and Fleischman.
Alan Smithee (what a great director you are, by the way) – the Slow Glass story is one I read a long time ago and loved. I wish I could find it again. But what I remember is this - A couple is driving along when they see a stand along the side of the road where a man sells ‘Slow Glass’ that he makes. They look at the various pieces of glass and mention is made that the longer the light takes, the more expensive the glass is. It can take up to 30 years or something for the light to pass through the glass and out the other side. They talk to the man who makes it, and you can see his family inside the house trying to get him to come in (it’s dinner time). His wife waves to him and tells him to come and eat. The couple asks why he won’t go in and the man sadly says that his wife has been dead for years and the image you see in the glass was created when she was still alive. That’s how I remember it.
Quoted from http://www.sff.net/locus/f65.html :
SLOW GLASS
Bob Shaw: (books) (stories)
Light of Other Days (ss) Analog Aug '66
Burden of Proof (ss) Analog May '67
They’re pretty good stories; he had a collection published with those and others.
And with a little more relevance to the OP, isn’t the cause of Cerenkov (sp?) radiation the sudden deceleration of particles travelling close enough to C to be faster than C-in-water?
Bob the Random Expert
“If we don’t have the answer, we’ll make one up.”
Amost. Cerenkov radiation occurs when particles pass through water at a speed greater than c-in-water. There’s no violation of relativity here since the “universal speed limit” is c-in-vaccuo.
Um… The point of my previous post is that Cerenkov radiation isn’t due to deceleration. The particle actually passes through the water (or other medium) at faster the the speed of light in the medium.
I assume, therefore, one could see Cerenkov radiation if a particle passed through glass faster than light would?
Geezer, could you remind me what the Moon Illusion is that you mentioned a while back? Thanks.
One final word on Bob Shaw: Like most SF authors, when he came up with “slow glass,” I don’t think he believed that such a substance could really be made. He was simply trying to invent a means of viewing the past that did not require the use of a Wellesian Time Machine or a starship travelling faster than light. It was a literary device that allowed Shaw to write a story about losing love to death (“Light of Other Days”) and about how technology affects justice (“Burden of Proof”), the same way we now use DNA evidence to get innocent people off Death Row. I think “Slow Glass” was an elegant solution.
(For that matter, Welles did not seriously believe it’s possible to build a Time Machine, either. It was a literary device that allowed him to present his speculations on the future evolution of Man.)
Bob Shaw lived from 1931 to 1996. There is an on-line bookstore in Australia named “Slow Glass,” apparently in his honor.
>< DARWIN >
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