Thursday, March 22, 2012

Can the Universe be Random ?

Does True Randomness Really Exist?

I once posed the question in an online discussion, is it possible that somewhere in the universe, there is a galaxy inhabited entirely by clowns riding unicycles? Absurd as the question is on its surface, it makes a point about true randomness.

Present models of quantum physics rely upon the concept of true randomness. A familiar example involves the decay of radioactive atoms. Uranium 235 has a half-life of about 713 million years. As you all know, this means that given any sufficiently large sample, half of the atoms (give or take a few) in the sample will have decayed during the half-life period. Of the remaining atoms, another half will decay during the next 713,000,000 years, leaving a quarter of the original sample. And so on.

But what about a single, specified atom? When will it decay? Here is where quantum physics relies upon true probability. For according to quantum theory, there is absolutely no way, no way at all, to predict with any reasonable precision when that particular atom of U-235 will decay. The best guess could easily be off by many millions of years, and perhaps by billions or trillions, or more, years.

Instead of guessing in this manner, what physicists say is that, during the half-life period of U-235, the decay of that atom has a fifty percent likelihood of occurring. But the precise moment of that decay, if it does occur, is utterly unpredictable. In other words, within the parameters of the half-life probability period, the decay will happen at a truly random moment, if at all.

It is important to note that pseudo-randomness is not at play. Pseudo-random number generators are not truly random. And in the macro world, even such seemingly truly random events such as coin flips and dice rolls are not truly random. They are the result of inputs which, if all of them were known, could in principle predict the precise outcome every time.

Therefore, Einstein was wrong in phrasing his objection to quantum theory. God may indeed throw dice. That would not violate Einstein’s conception of physics as inherently deterministic. The real question is (tongue in cheek), does God throw uranium?

Einstein insisted (as far as I know, for the rest of his life) that there is some unknown factor at work in quantum physics that causes the inherent uncertainties of quantum events to collapse into specific outcomes, thus eliminating true randomness from physics.

The idea in QP is that the only factors at work (in context of the foregoing) are the mathematical rules of probability itself. But if one thinks about it, there are two reasonable objections to that view. One of them has to do with physical causation, and the other is the more philosophical question, does reality ultimately make sense?

First, the matter of causation: To use a familiar example, if one throws a rock, it will move in the direction of the force propelling it, and follow a trajectory that is predictable if one knows all the inputs. This (albeit simplified) is due to the everyday rule of cause and effect. If cause A happens, then effect B must also happen.

Police ballistic science relies heavily on the fact that if enough is known about effect B, then one can trace back with great precision to determine what cause A was. Where was the bullet fired from? Many a killer has been caught by answering this question.

But according to QP, we could know absolutely everything about effect B, and have not a clue as to what cause A was, beyond a few vague principles. And this is true not only for a single electron, but even for scales of the macro world. After all, every macroscopic event is composed of countless subatomic events. Of course, at the macro scale, the statistical probabilities are so immense as to constitute certainty beyond the faintest doubt that a sane person could have. Even so, there is nothing in probability that prohibits the least probable event from actually occurring. Quite to the contrary, eventually, given enough opportunities, the least probable possible event must at some point occur.

This will bring us to the second objection concerning true probability. But before doing that, a final thought is in order. If the cause of the precise timing of a quantum event is pure probability alone, and if in principle there is no more cause than that, then in effect are we saying that, beyond the vaguest abstraction, there is no cause of anything?

Now, on to the second objection, which springs from the first. Does reality (in principle) make sense? Can it, if true randomness exists?

As we already pointed out, according to the laws of probability, given enough opportunities, even the least likely of all possible events must occur. In a universe of infinite proportions, and therefore infinite possibilities, it has been said that “everything that can happen, must happen.” Dr Brian Greene stated in a discussion on You Tube beginning at approximate video time 59:00, that “the mathematics doesn’t allow any possibility to go unrealized. All roads are traveled in the quantum multi-verse.” (He does, however, express a doubt that the final stage of this idea has been verified.)

If one contends that physical reality is infinite (whether a single infinite universe, or infinite numbers of finite universes), then the laws of probability do seem to affirm Dr Greene’s statements. Everything that can happen, must happen.

Putting aside the question of what decides what is possible (if infinity is the context), let’s consider the implications. We already mentioned that uranium 235 decays. It is statistically improbable, but not impossible, that every radioactive atom in the observable universe could simultaneously decay. The improbability is so low as to be considered impossible.

But not only is it possible, it is theoretically inevitable that, in some vast expanse of galaxies somewhere, in an infinite reality, just exactly that is happening, and will continue to happen, in infinite numbers of events, at unpredictable moments.

True, massive catastrophes do happen even in the visible universe. I saw it stated that a gamma ray burst in one galaxy could sterilize a neighboring galaxy, and that this likely has happened. It could happen to us, with no warning at all.

So there is nothing inherent in nature that says we cannot be vaporized at any instant.

But science works on the proposition that, overall, on the grandest of scales, reality does make sense, and that we can discern, at least to a large practical degree, what that sense is. Localized, seemingly senseless disasters can indeed occur. But that is a different thing than to say that at its core, reality makes no sense. Were that the case, science would be futile.

This, if my intuition about Einstein is correct, is why he could never accept the idea that true randomness exists. To him, the universe must make sense. To him, making sense was the same as determinism.

In my fallible view, even determinism itself would render the universe senseless, because determinism (as does randomness) rules out the most essential ingredient of any scientist, that of free will.

If a quantum event can be triggered by a purely mathematical abstraction, that of pure randomness, then it would seem pointless to try to trace backward beyond that trigger, to ask, what triggered the trigger? The pure randomness itself, constrained only by rules governing statistics, becomes a sort of force outside of the physical world of cause and effect. It becomes a cause unto itself. (May I say, tongue in cheek, a cause without a rebel?)

If physics can accept such a thing, then it seems but a small further step to posit that our personal sense of free will is not an illusion entertained by synaptic bundles (our brains), but rather, that free will is, analogous to true randomness, an untraceable force of causation in the physical universe.

If it is, if there is an as yet undetected dimension from which emanates randomness and free will, then perhaps Einstein’s description of scientific endeavor is spot on. He described his work as an attempt to “know the mind of God.”

Perhaps the unlikely and random events that gave rise to our universe, our planet, and ourselves, were neither unlikely nor random.

If the universe is truly without purpose or plan, but only blind, indifferent and random, then I will use another of my favorite analogies. The universe is at its core, a bad Monty Python movie, or much worse than that, a good Monty Python movie.
A correspondent replied to my brief treatment by mentioning that quantum decay occurs because of quantum tunneling, an event that occurs inside an atomic nucleus. He further described this tunneling as inherently unpredictable. But that is not precisely correct. His mistake is a very common one, that of confusing true randomness with our failure to predict an outcome. The difference may seem trifling at first. But in the context of the subject matter, it is all the difference in the world.
Here is what I said in reply:
It is important to distinguish between practicality and principle. (I'm speaking of course in the context of physics, not of morality.)

As a practical matter, a die roll is not (assuming fairness) predictable, because the variables are too numerous to handle.

But this does not mean that the die roll is truly random, because if, and this is in principle, if all the inputs could be known and calculated, the outcome is a certainty, unless quantum probability gets involved at the macro level.

Likewise in a deck of shuffled cards, it may be impossible (as a practical matter) to know what the top card is in the deck. But in principle, "nature knows," (so to speak) what that card is. It is not truly random. The three of clubs does not oscillate between rank and suit.

Therefore, the internal dynamics of a nucleus would be, in principle, not in practice, deterministic if the alpha particle were not a probability wave.

But since quantum mechanics defines the alpha wave as a wave of probabilities, then the tunneling effect is truly random as to timing.

However, if in some far flung future, science is able to delve deeper into the actual mechanism that "triggers" a quantum event, then there are many possible explanations, ranging from determinism to probability, but also including presently unknown forces, such as a concept of true volitional free will. That, in turn, might explain why conscious perception collapses a probability wave.