The Oxford Dictionary defines intuition as “the apparent ability to acquire knowledge without inference or the use of reason.” We all have these hunches about how certain things will behave, which, mostly unconsciously, are based on our earlier experience with this type of thing. If you see for example a car approaching on the street, you can easily tell whether or not you’ll have time to cross the street before or not, because this situation keeps repeating itself. Our intuition is formed by our experience.
This is the problem with forming an intuition for physical theories that are far removed from our daily life experience. Our judgement is good for Newtonian physics. We rarely experience directly an object of relativistic speeds (i.e. near the speed of light), let alone move at relativistic speeds ourselves. And when have you last come close to an object heavy enough to bring general relativity into play, say for example a black hole like it can be found at the centers of many galaxies?
This is why the predictions of General Relativity seem incredible and strange at first, they just have nothing in common with the view of the world we have formed based on our daily experience. An effect like time dilation never happens to us (while on the other hand, every child is familiar with the Doppler effect).
The same is of course true for Quantum Mechanics. We simply cannot experience directly the behavior of single elementary particles.
But the case is not hopeless. Luckily, the human brain is so powerful that we need not rely solely on our direct sensory experience to form an intuition. It is enough to think about a certain abstract concept and its implications for extended periods of time to form an expectation for how similar concepts will behave. Experiences can take place exclusively in your head, they will be an equally good guide as the intuitions that were formed on the basis of real life experiences. Already after one semester of studying General Relativity, its implications seem much less mind-boggling than when we heard about them the first time. But this is merely the beginning. If you have spent a lot of time doing a particular kind of calculation, you will know that a certain result is wrong just by looking at it, and before re-checking everything step by step.
Sometimes it is said about a famous scientist that he or she has this great “physical intuition”. Guess what: they were not born with that. They simply spent a very large amount of time thinking about their physical models, toying with example calculations and tinkering around with them, wherever they were, including scribbling on napkins while waiting at the restaurant. They are able to see connections others could not see because they have seen so many similar things in their life as scientists. This acquired knowledge needn’t manifest itself as a rational thought process. It can really feel the same as just “having a hunch”, it’s having a vague, fuzzy feeling about how a certain thing should work or how some object should behave, even if this object is an abstract concept.
I have already seen this kind of intuition in action in more senior people I have worked with. And sometimes it even happens to myself that I find myself telling someone that a certain thing should work like this because I somehow just know that it must behave like that.
