For a few years before escaping the extraordinary gravitational pull of my university, I served as a tutor and lab demonstrator for some first year physics units. From time to time I would find myself reliving the same argument with yet another student, over and over again — an argument that would inevitably start with this:
Will we ever use relativity/quantum physics/particle physics? Why learn it?
There are many ways to answer this question. One could make a grand speech about the value of learning things that aren't obviously useful, or claim that our innate curiosity should be fed with a range of intellectual foodstuffs, or talk to the fact that university is all about learning bizarre and wonderful things. But... well, these are all a little bit patronising and a far too general. There are plenty of not-obviously-useful things to learn, some of which really aren't useful to learn, ever. Morse code, for example. Repair techniques for the fire-lance. How to maintain a MySpace page. Latin. What makes particle physics different from these things?
In fact, underneath the need to answer this question for a student was this: if I didn't have an answer to this question for myself, why was I even teaching it?
I admit that what follows isn't a perfect case. There's still room for argument here — but that's fine, because the decisions about what to teach or what to learn are entirely subjective. So this is about as close as I can get to articulating why I thought it was worth (a) learning and (b) teaching.
Imagine you go to see a doctor about some minor complaint. During your visit, you make some comment about DNA.
D N huh? the doctor asks.
You clarify — you meant DNA, as in deoxyribonucleic acid, the building blocks of life, the mechanism by which we inherit certain traits from our parents, the famous double-helical structure of which was proposed in 1953 by Watson and Crick.
Oh, the doctor shrugs,
I don't really know about that stuff.
Would this not alarm you? The doctor to whom you have taken your sick, ailing cells has no idea what DNA is! Your attempts to explain base pairs, genes, RNA, mutation and the X-Men are just met with impatient disinterest. More than sixty years of profoundly game-changing concepts are just a vague, irrelevant concept to the person you are asking to make you better with modern medicine!
But hang on, says your doctor,
what do you care? Your ailment doesn't require any application of the details of DNA, so what's the problem?
So ask yourself: wouldn't this bother you anyway? It would sure as hell bother me. Why? Well, I suppose I'd expect that someone who's meant to be a specialist in biology and physiology might actually be up to speed on recent developments. I'd be a bit worried if medicine seemed to be the least interesting thing in my doctor's life. If they don't know about DNA, how interested are they in being well equipped to help me with problems I don't understand myself?
But DNA is frontier stuff compared to quantum mechanics! Einstein won the Nobel Prize for explaining the photoelectric effect in 1905! He'd already tackled special relativity by then too! Particle physics was in full bloom by the 1950s!
So if you expect a medical doctor to know about DNA, shouldn't you also expect a civil engineer to know about modern (ie. post-19th century) physics?
Now it might sound like I expect a chemist or mechanical engineer or biologist to be able to solve problems in general relativity off the top of their head years after they graduate. I don't. What I'm getting at is that when you're an engineer or scientist, part of your job is simply knowing how the things around you work. Most of the things around us — including tools you will use for your own work — function using concepts in physics that are well under a century old. If you don't understand them, you are simply not as good at that part of your job as someone who does. You will forever be a consumer, rather than a producer, of new ideas and their applications.
If you're fine with that picture, then the answer is actually: you probably won't need this stuff, ever. Otherwise, pay attention, because it's awesome.