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The Argument From Quantum Physics

by Francois Tremblay



The quantum world has only relatively recently been discovered. The first major steps in this exotic place were taken by Niels Bohr, a physicist of the early 20th century, around the time of Einstein. While Einstein’s grand theories of general and special relativity predicted that the universe was, on any arbitrary scale, arbitrarily predictable. That, given enough data about a situation, any previous or following situation could be calculated using his laws of the universe. Niels Bohr, on the other hand, took a more probabilistic approach, and experiments and theories have confirmed again and again his results. Today, the game in physics is to unite the quantum world with the relativistic world, but that is another story. For today, we shall concentrate on Niels Bohr’s quantum universe and its implications on an omniscient God.

Oddly enough, the foundations of quantum mechanics lay well within Einstein’s realm of study. It was he who first discovered that light, that “substance” so fundamental, we all perceive it all of the time (unless you’re blind, but then of course you’re probably not reading this article). But what exactly is that substance? Well, if you’re not a physicist then it may come as a surprise that light, and everything else for that matter (pun intended), is part-particle, part-wave in nature. (For information on the wave-particle duality: http://www.qmw.ac.uk/~zgap118/.) And as Niels Bohr discovered, this wave can be conceived of as a probability wave. A wave which determines the probability that a particle’s properties will be measured right here or over there, or anywhere else in the universe. But the fact remains that a particle—the spot at which we do see an object’s properties like mass, charge, and color—exists only at one location.

Niels Bohr thus had an interesting idea: What if the probability waves could interfere with each other, like sound waves, or waves travelling down a slinky or piece of rope? What kind of phenomenon would this produce? Sure enough, probability waves can and do interfere, and this is where a most queer experiment begins to form.

The experiments I will be speaking about are known as slit experiments, and are well known to most physicists and anyone interested enough in the subject of particle physics. You may have read about these experiments in articles or books on the Heisenberg Uncertainy Principle. The way they work is quite simple: a pinhole (or 2 or 3 pinholes) is punched in a thin sheet of metal or other material. A laserbeam (that is, a beam of uniform light) is passed through the pinhole, and projected onto a photo-reactive plate, much like light that passes through your camera onto photo-reactive film. The plate will show luminescence or return data about where photons have touched down, and scientists can record and analyze this data.

The first version involves a single pinhole—the Single Slit Experiment. In this experiment, light shone through the pinhole forms a diffraction pattern, since it may diffract through the pinhole and hit the plate at an angle. You can almost think of it as a ball being thrown off a wall at different angles—it may not always hit the ground in the same spot. This version is interesting, and it proves that light does indeed have a wave-nature. But aside from that, there is not much to be said about it, pertaining to atheism and an omniscient God concept.

The second version has much more far reaching implications. When light is passed through not one, but two pinholes, or slits, it creates an interference pattern meshed on top of the diffraction pattern from the first experiment (Picture). Interference occurs when 2 troughs or 2 crests of a wave line up, and cancel each other out or double in size. This may seem reasonable—after all, millions and billions and innumerable photons shoot out of a laser beam every second, and so some of their waves line up or cancel each other out—right?

But, what if we slow down the laser beam, and shoot not billions, thousands, ten, or even a single photon through per second? What if we pass a photon through the double slit once every minute? Once a week? Once a decade? The result will consistantly be the same, and interference patterns will leave their mark. The probability wave of an individual photon can interfere with itself. Even at such low rates, the unmistakable pattern (as pictured above) is clearly visible. Why? Well, even when only one photon goes through at a time, the question remains—which slit did it go through? If they all went through the left slit, there would be no interference as in the single slit experiment. If they all went through the right slit, there would again be no interference. Could it be that their probability wave goes through both slits at the same time? This must be the case, or there would be no interference pattern at all. But a photon is only a particle, and as we all know particles must take a definite path. How can we solve this puzzling riddle?

The answer is not quite as simple as one might hope. In fact, it is this quasi-paradox that leads us to the argument for the non-existence of an omniscient god.

Let’s reform our experiment a bit, and put a detector on each slit. This way, we can record which photon goes through which slit—since after all, as noted, a particle can only take one definite path. This seems like a change that can’t possibly affect the experiment—it is extremely passive in its detection. But the reality is that with knowledge of which slit a photon passes through, its probability wave is almost “forced to decide” which slit it must travel, and the interference pattern vanishes. This aptly named which data, the knowledge of which slit a photon passes through, seems to ruin our entire experiment.

You may be wondering, doesn’t the detector “nudge” the photon at all? While the detector must interact (disregarding entanglement) with the photon in some manner, of course, we may place the detector anywhere along the path to the screen. It may be halfway between the slit and the screen, or just before the screen, or anywhere else for that matter. (Another version of this experiment can be performed where the light comes from stars halfway across the universe, that has been travelling for billions and billions of years.) So, hasn’t the wave been forced to choose a distinct, definite path already? Not quite. The quantum laws that describe this phenomenon show that a distinct and definite path is chosen if and only if the which data is present. If there is no knowledge of its path of travel, then it will choose both. And this is the heart of the problem.

I didn’t intend for this to be an article about quantum mechanics—as interesting as they may be, they are not the topic of this website. Unfortunately, there is not much left to say about the atheistic argument to be made from these so-called quantum superpositions, and the result is almost obvious at this point. Surely, god has all which data available, from every quantum phenomenon that has ever happened, is happening, and will ever happen in our temporal universe. But if the world view in which this is a reality holds true, it must account for all known laws. That is to say, if we see a single quantum superposition that has not collapsed (it is said to collapse if the which data is known), then the idea of an omniscient god must be ruled out forthwith.

We live in a puzzling universe indeed. But it is not so puzzling to realize that an all-knowing god, and the god concepts inherent in almost all world religions, is inherently flawed. Ah, the irony, of using the Principle of Uncertainty to prove, with certainty, that god does not exist.

Thanks to Richard Harter for first thinking of this elegant argument for strong-atheism. Here is my reformulation in a syllogism:

  1. The god-concept designates an omniscient and omnipresent – all-observing – being (i.e. its knowledge effectively observes all phenomena).
  2. Observation collapses quantum superpositions.
  3. An all-observing being would automatically collapse all quantum superpositions. (from 2)
  4. We observe that not all quantum superpositions are collapsed.
  1. Therefore, gods cannot exist. (from 1, 3 and 4)

Last updated: April 30, 2005