Today I want to talk about quantum entanglement. No, not the details but the idea of entanglement and how it, and other radical ideas like it, can challenge our intuition. Sometimes, either in our research or in our everyday life, we come across some process or some result that puzzles us and defies our understanding because it is “not intuitive”, as if our intuition were a constant of life. I don’t think that intuition is a constant. It shouldn’t be, otherwise we would not have survived millions of years of evolutionary pressures.
Newborns do appear to have some innate expectations about how the world works, but in a very limited way. Their intuition grows as they experience colors, shapes, sounds, smells, etc. First they are puzzled by the new experiences but, with repetition they incorporate them into their model for how the world works. Little by little, they expand their “mental horizon” and grow as individuals and are able to tackle new and exciting problems such as, writing a text, solving an equation, riding a bike, filling out a tax form (I’m still working on this last one).
Personally, the biggest challenge to my intuition occurred when I first learned about special relativity. The whole idea of how fast you move influences how time flows is a very radical one. For me it was completely counter-intuitive at first. But, with enough exposure to relativity problems (some of them quite disconcerting), I eventually developed an, albeit rudimentary, intuition for how reality seems to work at scales of vast speeds and distances. During my senior college year my friend and I did a final class project on wormholes. A wormhole is a theoretical shortcut in space-time. It is not a black hole, nor a white hole, nor does it allow instantaneous travel. It’s just a tunnel made out of “exotic matter” (matter that expands when you try to squeeze it). We actually solved the equations of a wormhole and figured out how a traversable wormhole would work (hint: it’s kinda hard to build one). It was one of my favorite physics problems but I would not have been able to solve it had I not first developed my relativity intuition.
And now quantum entanglement. Again, when I first learned about this concept, it was not easy to grasp. Not only did I have to deal with the fact that atoms and their constituent particles cannot (usually) stay put in any one place – the quantum part – but also that these particles can sometimes influence each other’s behavior instantaneously regardless of how far apart they are – the entanglement part. Yet, perhaps because I took quantum mechanics after relativity, it didn’t require that big of an effort to understand the basics of entanglement – the results were not that counter-intuitive. Quantum entanglement was first mentioned in the mid 1930s and has been demonstrated experimentally many times ever since. And yet experienced researchers developed entire alternative theories to quantum mechanics because they refuse to accept the idea of apparent instant influence between particles. Their reasoning is that there are these loopholes in a particular type of experimental test which, because they have yet to be all closed in one single experiment, can render quantum entanglement invalid. Every new experiment that is performed comes closer to closing all of the loopholes, but we are not quite there yet. We may never be able to convince the skeptics entirely because one particular assumption of these experiments is the existence of free will. Yes, there are alternative theories to quantum mechanics which are completely deterministic. Refuting them implies proving that free will exists. How do you prove that?
Fundamentally, the problem with intuition resides with the notion that all processes in the universe should be similar to those of our everyday experience. But really why should this be the truth? There is absolutely no evidence that it should. In fact, every experiment performed, from those in the realm of really big things (planets, stars, galaxies, etc.) to those in the realm of really tiny things (atoms, photons, quarks, etc.) shows that, in fact, the universe does behave differently at different scales. We don’t know why this is the case. But that’s okay. I believe we will eventually have an answer. All that matters is that the scale at which a process occurs matters greatly.
When we are learning about something new, we should be prepared to be confronted with non-intuitive events. When these events are repeated and have gathered enough momentum, then it is okay to start including them in our mental picture of the world and make them intuitive in the future. As long as we keep challenging our intuition we get closer and closer to understanding the ultimate question of life, the universe, and everything.