"Physics is like sex: sure, it may give some practical results, but that's not why we do it."
- Richard Feynman
I have been asked this question countless times and I would like to rephrase it: Why did you want to have a messy desk? Last Monday, I was asked this question once again but it took me six days to write a proper answer. It is not that I didn't have an answer, it is just that I was too busy having fun with physics.
Indeed, I have a problem to solve. What is the electromagnetic field like near a fast moving charged particle? This problem was already solved by Alfred-Marie Liénard in 1898 and independently by Emil Wiechert in 1900. However, my task was to go a step further. I had to write the same expression in covariant form using outer derivatives, that is, in non-coordinate form. I derived it. But then I had to prove it. I tried. Wedge products, outer products, inner products, 4X4 matrices, 16X16 matrices, tensors,... More than 50 pages and still not proven. My strategy is simple, if I am short of ideas, I drink coffee and take a nap. Thus, I'm sure of waking up in 20 minutes with everything in my head refreshed. I did just that yesterday and when I woke up I got a new idea and decided to prove my work this way. Was it right? It seems right, The electromagnetic tensor is a rank-two antisymmetric tensor. I've seen the four zero components, I've seen the antisymmetry, there are no weird components. But the laziness of physicists is not a secret to anyone, so I kept this work for today.
There are two possibilities: If I am wrong, then I'll try even harder to prove it, I'll ask for help, but I'll prove it. That's passion. If I am right then, I will be happy but not satisfied. Another question will arise. What happens to the electromagnetic field when one gets nearer to the particle? Quantum effects will need to be considered in that case. And what if the particle is in a strong gravitational field? The theory will then include general relativity. And what if we get very close to the particle, let's say a distance of about 10^-34 metres ? All hell breaks lose. The laws of physics as we know them just don't work anymore. String theories(which one?), superstring theory, quantum loop gravity? We just don't know which we to go anymore and we want to go anyway. We want to unveil the secrets of the universe, to read the mind of god(metaphorical). That's curiosity.
Fun, laziness, passion, curiosity and the ability to be happy but not satisfied are the reasons why I wanted to become a physicist. I'm sure that there is a consensus on this matter among all types of physicists, from particle physicists to cosmologists. We understand that we are the most important people on earth and that we are the pinnacle of human knowledge and that the future of humanity lies in our minds. I'm not being pretentious but Faraday's law of electromagnetic induction runs the economy and Einstein's mass-energy principle ended the second world war :) But that's not why we do it. We do it for love.
“I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.”
― Isaac Newton