March 06, 2002

I don't think anyone will deny that quantum physics is one of the weirdest fields of science. Describing the very, very, very small can cause some serious strangeness.

One of the classic experiments that I saw all the time in high school textbooks involved a gizmo called an electron gun and two plates of metal. One plate of metal had two slots, side-by-side ( || || ) in it, the other was coated with a special material that was sensitive to electrons. The slotted plate was put in front of the coated plate, and the electron gun was put in front of the slotted plate. The electron gun was designed to "shoot" electrons one at a time toward the coated plate, thereby making them go through the slotted plate.

Easy enough. The electron must travel through a slot on its way to the coated plate. The weird part was what happens when the experiment is performed. The electron has a random chance of going through one slot or the other. If you use instruments to record which slot each electron goes through, then at the end your coated plate looks like a gun target... lots of dots. However, if you don't watch to see which slot the electron goes through, you don't get any dots on your coated plate. Instead you get a wave pattern, as if blurry light were being shone through.

Why is it doing that? Well, according to quantum mechanics, in the second experiment the electron is going through both slots at the same time. You know it's a single particle, because that's the way the machine is designed. It doesn't shoot more than one. Yet you get a pattern like waves of light rather than single particles.

The wave forms represent probabilities. Imagine one racehorse in one race on one day. A huge number of factors can affect the performance of the horse... the condition of the track, the weather, the jockey, what the horse ate, etc. By taking all these factors together, bookies make an educated guess as to where the horse will finish in the race. These guesses are stated as odds. 50:1, 20:1, 5:1, and so on. Well, the patterns on the coated plate represent the odds that each electron had going through one or the other slot. A subatomic horse race, with only one horse. A horse that has the ability to win, place, show, and come in dead last all at the same time.

Calculating the odds for these sorts of particle interactions is extremely complex. So complex that there are only a handful of physicists that can describe the formulas needed to figure it out.

And yet, strangely, it has been discovered that those calculations are nearly identical to certain kinds of calculations needed to distinguish sound from noise. The same calculations that you and I do every day when we hear our names called in a crowded room.

Posted by scott at March 06, 2002 09:23 PM

eMail this entry!

Scott, that is way too complicated for me.

Posted by: Pat on March 7, 2002 11:03 PM
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