THE NAKED ONTOLOGIST: Weekend At Bernie's 2: Electron Boogaloo (2 of 5)

To see electrons do their boogoaloo, you need a special apparatus for them to use as their dance hall. You need a device that can fire electrons in streams, or in tiny bursts of single, isolated particles one at a time. You need a box with a hole on one side for the electrons to shoot through into the box and a pair of slits on the other side through which to leave the box. You need a wall on the other side of the box (the one with the slits). You need the wall to have a special material fastened to it that will react to the presence of electrons and make the impacts of electrons on it visible.

The dance takes place in steps. The last step is the really dramatic one. First you cover one slit - either slit will do, and fire up the electron gun. It doesn’t matter whether you have the gun set to fire a steady ray of electrons in a constant stream of bombardment, or to only release one electron intermittently at intervals - it will show the same thing - in the latter case it would just take longer for the individual electron impacts to form the pattern. The pattern when one slit is covered is a single band (the shape of the one uncovered slit) on the wall beyond the box. The electrons, whether in a stream or all alone, act like individual particles, or at least the wave characteristics are not detectable during this first step of the dance.

For the next step you uncover the slit that you had covered and fire the electron gun to send out a stream of electrons through both uncovered slits. If electrons were merely particles, you would see the two-slit pattern form behind the wall, but that’s not what you see here. You see several bands, the ligher, weaker ones closer to the outer edges, the strongest ones toward the center. That is an interference pattern. It shows that the stream of electrons is propagating like a wave of electrical energy. When waves are broken up into sets of waves as they bisect to pass through the slits, the sets of waves interfere with each other - their crests and troughs cancel each other out. In between those cancellations there is a richer degree of interaction. The net result is an interference pattern more complicated than the behavior of single discrete particles confined to a definite location or moving in a definite trajectory.

Ok, you might argue, that may be interesting, but that doesn’t mean individual particles do that. We fired a stream of many such particles, so perhaps it is no surprise that they would interfere with each other and move in a wave. What would happen if we fired single electrons intermittently one at a time through whichever of the two slits each would happen to go through? (Note for later that there is no causal explanation, no physical fact, known or unknown, that determines which slit an electron will exit the box through). If electrons were merely particles then surely now all we’ll see is two bands slowly form from the accumulation of marks from individual electron impacts.

Third and final step - intermittently fire individual electrons through the two open slits and see what happens. So what happens? Does a two slit pattern form?

No! An interference pattern emerges again! How can that be? It is only one individual electron (presumably) going through only one of the slits at any given time! What could be interfering with the electron if not other electrons in a stream? What could be causing the wavy behavior of an individual electron?

The electron is, in that instance, a wave interfering with itself. And what is interfering with what? The answer is that different possible states of the electron are all co-existing in a strange, foggy quasi-reality of less than full actual potentials. The possibility that the electron goes through the left slit is interacting with the possibility that it goes through the right slit. In a very real and valid sense, the electron, even as a single particle, goes through both slits at the same time! In another sense, it does not actually go through either one. In fact, in a very real sense, according to the equation governing subatomic wave collapse, the electron does not have any definite position or single trajectory until after it impacts on the wall and is thus observed and measured.

That is the Electron Boogaloo - a dance where a tiny particle is not just Here or There, but Kind of Here and Kind of There, and Kind of Nowhere, and Kind of Everywhere At Once. The dance hall scenario is known to science as the Double Slit Experiment.

Check out this video on youtube. (url link here: http://www.youtube.com/watch?v=DfPeprQ7oGc ) It illustrates what I have said, and also adds an important point I have left unsaid, simply because it is unbelievable. It is true, but you won't believe it. You can also click the image below: