Monday, 19 December 2011

On attempting to understand the universe

Horribleness of tomorrow: oral exam in particle physics. Strangely enough I'm hardly even terrified. I seem to have adopted an air of "meh"-ness. It will work out or it won't, really. Nothing to panic about. ARGH who are you and what have you done to the usual nervous wreck that is me?

I spent a couple of hours yesterday reading a little about string theory. Dug up an essay on it that I wrote four years ago, in high school. Read through it and realised sadly that I don't know more on the subject now than I did then, not even after three years of physics studies. That is kind of the feeling I've got from this whole particle physics course, really. Everything is kind of simple and neat — there are a number of quarks and leptons and bosons and interaction rules and Feynman diagrams and whatnot, but everything seems to be really hand-waving. There is all this talk about symmetries and resonances and other concepts I thought I had an idea of the meaning of, but their meaning here seem so arbitrary. The further the course have progressed, the stronger the suspicion has grown that the math behind these theories is so impenetrable that it isn't even worth beginning to investigate it in a five-week course on the subject. It is both scary and depressing that it would probably take at least five years of hard studies on the subject before I would even begin to understand what it is all about. And then it would probably only be to discover that even the theory itself is far from complete. Exhilarating, yes, but also more than a little frustrating.

But not to worry, I'm inspired enough to get me through a couple of years worth of exams. One of the guys who won the Nobel Prize in physics this year, Brian Schmidt, gave a talk at the university last weak. I simply had to go there. I mean, they got the prize for the discovery of one of the most awesome facts of the universe: it is not only expanding, its rate of expansion is accelerating. So how could they tell? Well, allow me to go astrophysics populariser on you a bit.

They have been looking at galaxies other than our own, many millions of light-years away out there in space. The first problem that needs solving is: how do we measure their distances? Well, we know a couple of basic properties of light, and more precisely luminosity. Luminosity is a quantity that can be measured by sensitive instruments, and we know that it decreases as one over distance squared. Therefore, if we know exactly how bright some distant object is shining, and can measure how bright it appears to be shining all the way over here, the object's distance can be easily calculated. Fortunately, there are objects called type Ia supernovae whose luminosity is always the same, and we know this at a very high degree of accuracy. So when we observe such supernovae in distant galaxies (and although rare they are easily recognised), we know how bright they really are, compare with how bright they appear to be, and can calculate their distance. Yay!

But how do we know their velocity? Then a physical concept known as Doppler effect is an important phenomenon to take into account. Light waves, as they travel through space, experience so-called redshift as an effect of journeying through space towards an observer whose velocity differs from that of the light-emitting object. Their wavelengths stretch out, blue light goes redder, simply put. By studying spectra of absorption lines (alright I'm sorry I don't have the energy to explain every single term right now... just think of rainbows with black lines in them?) and noting how much farther to the red or the blue end of the spectrum these have moved, it can be deduced at what speed and in which direction the studied object is moving compared to us.

It turns out that all galaxies, including our own, are moving away from each other. It is also the case that galaxies further away seem to be moving away faster than those nearby. The conclusion to be drawn from these observations is that the galaxies are not just moving away from each other within space, but space itself is expanding, and its expansion rate is accelerating. If things continue like this, then in a couple of billion years we won't be able to see other galaxies since they will have moved beyond our observable universe (disregarding the fact that we all will be long-since dead by then). A mind-boggling thought, eh?

Definitely. But apart from the slight sea-sickness i cannot help but feel a strong urge to investigate this universe until it reveals more of its secrets. And although I'm surely one of the least bright persons aspiring to conduct research on the subject, I hope I some day will at least get to be a part of some kind of discovery. Could there be a deeper satisfaction after a hard day's work than knowing you have expanded the boundaries of human knowledge, even if just the tiniest bit? Not for me, I think. Wow. Maybe I'm going to be a scientist when I grow up, after all.

In the meantime, please reflect on this quote from an excellent book I recently read. I think it summarises my sentiment on knowledge after three years at the university quite well.

Before I heard him talk, I was like everyone else. You know what I mean? I was confused and uncertain about all the little details of life, but now" [...] "while I'm still confused and uncertain it's on a much higher plane, do you see? And at least I know I'm bewildered about the really fundamental and important facts of the universe.
— Terry Pratchett (Equal Rites)

May your minds stay clearer than mine, dear readers.

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