The logic of quantum physics


I was always more of a dog person myself...

I bet you more people have heard of Schrodinger’s cat than the Law of the Excluded Middle. I say that because people like paradoxes if they show how ‘fab and groovy, windswept and interesting’ they are, but how many people ask enough questions to resolve the paradox? That’s usually the job of scientists, but with quantum physics and Heisenberg’s Uncertainty Principle those questions remain unanswered. In fact, it’s worse than that. In order to explain certain quantum phenomena, scientists have had to resort to suspending the laws of logic.

How can Schrodinger’s cat be both dead and alive? Paul Boateng once asked the same question about the Labour party at an Oxford Union debate on ‘zombie politics’. The answer was that it depended whom you asked. The Lib Dems wanted Labour to be dead, but the Conservatives relied on the party being very much alive! It’s the same in the world of astrophysics and quantum mechanics. If you believe Einstein’s General Theory of Relativity, you get one set of answers, but if you believe his Special Theory of Relativity you get another. The world of the very large and the world of the very small appear to behave according to different sets of rules. Admittedly, those rules make scientific experiments predictable to an astonishing level of accuracy, but they’re still different rules. Is it too much to ask that we have only one set of laws however big the objects we’re trying to describe?

Now, physicists are obviously working hard to reconcile these contradictions, but they haven’t got very far considering they’ve been at it since 1905!  What nobody seems to have done is to look at things from the other end of the microscope (or telescope): what if it’s not a problem with science but a problem with logic? What if the rules of logic that scientists have been following for thousands of years just don’t work? The Law of the Excluded Middle states that a proposition is either true or false, but it can’t be both. The Schrodinger’s cat thought experiment appears to be an exception to the rule, as the cat exists in a ‘superposition of states’ until it’s seen by a human observer. Now, in what other avenue of life do we accept that different versions of the truth exist in a ‘superposition of states’ or that cause and effect can be reversed? Do schoolboys only find out whether they’ve done their homework when their teacher opens their books? Can they then decide that they did it after all and see the answers magically appear like the keys to the jail in Bill and Ted’s Excellent Adventure? You can’t have your cake and eat it – unless you happen to be a quantum physicist…

Another case where logic is set aside is the nature of light, which is either a wave or a particle beam, depending on what you had for breakfast that day. You would think that it could only be one or the other, and that was certainly what I thought when my old physics teacher playfully asked the class which it was. What I didn’t know was that it was a trick question: it’s both! I thought he was just messing with our 15-year-old heads, especially as it was the last physics lesson before the summer holidays, but it turns out we’d just gone through almost the entire O-level syllabus without being told the whole truth. “You want the truth? You can’t handle the truth!” as he didn’t say…

Whether it’s photons or subatomic particles, physicists usually get away with breaking the rules of logic by invoking probability theory. Now, probability theory is just a decision-making tool and not any kind of explanation of cause and effect. The only reason we calculate probabilities is that we don’t possess complete information. If we toss a coin, we say the chances of it being heads or tails are one in two or 50%, but that’s just because we haven’t tossed it yet. Once we’ve tossed the coin, and it turns out to be tails, say, the ‘probability’ of that outcome collapses to 100%. If it’s tails, there was actually never a chance that it was going to be heads. It’s just we didn’t know all the variables such as how high the coin would be thrown or how fast it would be spun. With perfect information, probabilities are meaningless. However, quantum physics begs to differ. Whether it’s the rate of radioactive decay or the presence of electrons at different energy levels, outcomes are given probabilities as if that predicts and explains the phenomenon. Making predictions is fundamental to the scientific method, so we surely deserve a better answer than, “Well, it might do this or it might do that…” Logic demands that there is no effect without a cause and that causality runs from the past to the future. How have we reached such a pass that both those ideas have been thrown out the window? People used to ask whether knowledge of the positions and masses of every particle in the universe would theoretically make possible accurate predictions of every single event in the future. The uncertainty principle seemed to put an end to such speculation, but not in my book. If probability doesn’t actually ‘explain’ anything, then you’re back to looking for good, old-fashioned cause and effect. Unfortunately, that throws into doubt a whole lot of notions we tend to take for granted. Take free will. How can I be said to make a ‘choice’ when it’s simply the result of a collision between subatomic particles…? Do we all have to be biological determinists now?

When it comes to very big things rather than very little, physics has similar problems. There is no such thing, we are told, as ‘action at a distance’, and yet that is exactly what the effect of gravity seems to be. Physicists would say that gravity is ‘explained’ as the curvature of space-time and that we can visualise it by throwing little balls ‘in orbit’ round a big, heavy ball on a trampoline, but that’s (literally) a circular argument because it relies on the existence of gravity to explain gravity’s existence! When a theory is no more than a visualisation or a metaphor, you know you’re in trouble…

And another thing…in fact, a very big thing. If every effect must have a cause and nothing in the real world is infinite, then how did the universe get started in the first place? Religion bumped heads with this one a few thousand years ago, but making any kind of god the ‘first cause’ or ‘prime mover’ just begs the question, “Well, if God created the universe, who created God?” That leads to an infinite regress. Again, scientists have an excuse. The accepted version of events suggests that talking about anything ‘before’ the universe began is nonsense because time was only created during the Big Bang. Well, they would say that, wouldn’t they…?! Unfortunately, the laws of thermodynamics don’t deal very well with the idea that a couple of particles of matter and antimatter just ‘popped’ into existence, collided, exploded and created the whole universe because of a slight imbalance. There’s no such thing as a free lunch – unless you’re Schrodinger’s cat, and we all know how that worked out…

Bertrand Russell upset the apple cart when he showed that the logical basis of set theory in maths was faulty, but nobody has done the same with science yet. Either science doesn’t stand up to logic or logic doesn’t stand up to science. Who knows which? The only stupid question is the one you never ask…

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