Boffins build 'slow glass' light-trapping nanodoughnut Warwickshire boffins believe they may be on the track of science-fiction "slow glass", through which light might take a long time to travel. The scientists think that such light-storing materials might be fashioned using excitons mounted inside unfeasibly tiny "quantum doughnuts". In essence it seems that an exciton is an …
The big flaw in Shaw's book was his explanation of how a coherent image was formed in the "slow glass". Since all the light from everything the glass can "see" impinges on the whole pane and then travels through and will be emitted omnidirectionally on the other side, there is no possibility of extracting an image from it (unless you buy his rather grasping-at-straws explanation).
Any practical use of this stuff, presuming it ever makes it into the real world, would be severely limited by this problem.
The RF and acoustic versions of these have various uses as memory devices (EG old dumb terminals and RADAR receivers) and it's possible to make them out of discrete components. This has never been possible with light except in the clumsiest of ways.
A litteral interpretation of it as Bob Shaw's slow glass (never got round to this one. Read most of his others) maybe reaching.
Intriguing.
I read an awful lot of of Science Fiction in my teens. The concept of "Slow Glass" is one of the things that has stuck with me ever since. As an example of pure "speculative fiction" it is heard to beat - a concept that is very simple to describe, and that can be understood by anyone, and that has a significant societal impact (the surveillance society mentioned in the article, scenery farms where sheets of slow glass with a period of years are set up to trap the view from a lake or a field, later to be hung in offices or living rooms, etc).
> You do know Shaw's book was a work of fiction, right?
Err, yes. The clue is in the name of the genre: Science Fiction. Now when you get round to reading the article, you'll notice a couple of phrases:
Such technology was imagined by renowned sci-fi scribe Robert Shaw .... and
.... could offer something on these lines ...
which when taken together (as you can safely presume, since they're in the same article) could lead to the conclusion that "slow glass"'s ability to reproduce images was on the cards. It's not, as the properties of the material wouldn't allow it to produce a coherent image. However, one of the side-effects of slow glass, and the main tenet of the book, was that it led to the ultimate surveillance society - something we probably are headed towards, just not like that.
That's the issue Pete was discussing in his previous two posts:
"Since all the light from everything the glass can "see" impinges on the whole pane and then travels through and will be emitted omnidirectionally on the other side, there is no possibility of extracting an image from it"
Pete's hypothesis analyses the light striking the outer surface of the glass as a wave, which is then propagated through the slow glass and transmitted omnidirectionally when it emerges on the other side. Considered as a particle, this means that any given photon would be transmitted in either a random direction or from a random location in relation to its location and the direction it was travelling when it entered the glass.
Given the Heisenberg Uncertainty Principle, which in essence states that you cannot simultaneously observe the momentum and position of a quantum particle, Pete's hypothesis would be correct.
Consider a photon travelling at C through a vacuum in a certain direction: this photon has a determinate momentum. Therefore, it can be predicted to pass through a given point in space at a given time. However, when the photon enters the "slow glass", it combines with an electron to form an exciton, as the article states. The momentum of this exciton is equal to the vector sum of the momentum of both electron and photon, and is thus changed from both. Furthermore, because this exciton is being constrained to follow a curved path in space by means of the "quantum doughnut" or torus, its momentum is constantly changing as long as it is in the torus - because the direction component of the momentum vector is constantly changing as it moves along the curve of the torus.
So in order to release the photon so that it is travelling in a determinate direction from a determinate location, which is required to recreate the image "seen" at the entrance point, would require that both the position *and* direction (that is, momentum) be determined at the same time - the very proposition that the Uncertainty Principle states cannot be achieved. Since this is the case, either the photon would be released in a determinate direction from an indeterminate position, or it would be released from a determinate position in an indeterminate direction.
Therefore, to answer your question, it is possible that the outgoing photon could travel in the same direction as the incoming one, but then it would be from a different location. If it were in the same location, it would then be a different direction. Ergo, no image, either way.
Er, what if, right... you fired a gun at a sheet of slow glass and the velocity off the bullet exceeded the speed of the slow downed light.
Would the bullet end up travelling faster than the speed of light. Or would it gain so much mass and stop, thus making the ultimate bullet proof glass?
Could I patent that idea and get rich from it?
Is this not a similar concept to electron trapping in phosphor crystals? We have cassettes with phosphor screens in them in our lab. You put in a dried electrophoresis gel labelled with a radioactive isotope (say P32 or S35) and the radiation promotes electrons to higher energy electron orbitals (e.g. makes "exitons") which due to the nature of phosphor electron orbitals stay there until given an extra jolt of light in a phosphorimager (something like a giant digital scanner that you put the screens onto), after which they release a perfect image of the radioactive areas of the gel.
A similar concept is used for image intensifiers (such as found in real-time x-ray machines and night vision goggles), although in this case phosphor crystals are used to convert light to a high energy electron beam in a vacuum tube, and then back to light after amplification.
These concepts have been in general use for decades so maybe not quite so sci-fi after all, just a higher-tech version of an old invention?
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