Thursday, 31 October 2013

Explaining the weird world of quantum mechanics

Quantum mechanics tells us things about the world that are impossible to make sense of. For example, it seems to tell us that a particle can be in more than one place at once. In fact, so the maths suggests, it can be in infinitely many. But then, putting aside the fact that this sounds ludicrous in itself, why is it that we only ever measure a particle to be in one place?

Human kind has always wanted to make sense of the world around us. When the ancient Egyptians saw the sun move through the sky, they understood it to be their god "Ra" travelling across the sky with the sun on his head. Thousands of years later, the Greeks, and later Copernicus, made sense of it by proposing that the Earth revolves around the sun.  Of course, these two theories are very different from each other, with the latter justified by a lot more evidence than the former. But they both try to explain.

Similarly, physicists and philosophers of physics are trying to explain quantum mechanics, but it is proving impossible to do so conclusively. According to the most widely accepted theory, a particle is in infinitely many places at once only until the moment it is observed or measured. At this point, it instantaneously and unpredictably takes up one position. A less conventional but increasingly popular theory proposes that when the particle is measured, our universe actually branches off into infinitely many others universes, with the particle assuming a different position in each of the universes. Thus, we only ever measure the particle to be in one place.

Neither of these theories seem very intuitive; rather, they both seem utterly fantastical. But when Copernicus proposed that the Earth revolved around the sun, that didn't seem very intuitive to his contemporaries either. What I think is really exciting is that something has to be right, and whatever it is, I feel quite sure, is going to be weird.

Friday, 25 October 2013

The reasons behind our fundamental constants

I've just watched an interesting talk by Gian Giudice. In this talk, Giudice presents his hypothesis that the value of the Higgs boson mass, which is approximately 126 GeV, is special: it is special because it falls within the small range of critical values that mean that the structure of our universe is on the brink of collapse. Luckily, the probability of such a collapse happening is so small, that this is only likely to happen inconceivably far into the future (phew!).

Of all the values the Higgs boson mass could take, why is it this one, one that puts the fate of our universe on knife-edge? Giudice believes that there could be a reason, using an effective analogy to explain why. Consider the much less mysterious phenomenon of sand dunes: the slope of sand dunes generally take a value between thirty and thirty five degrees, because the effects of the wind and the effects of gravity upon the sand mean that the slope is simply statistically likely to be within this range. And so the same can be said for the Higgs boson mass: there is a high statistical probability that its mass takes a value within the range that it does, due to two competing effects. What these effects might be caused by pose further questions to be explored.

This got me thinking about the other fundamental constants of the universe: Planck's constant, a fundamental constant of quantum mechanics; the speed of light in a vacuum, the constancy of which is the insight of Einstein's theory of Special Relativity; and the fine structure constant, which, if it were just four percent larger, would prohibit the formation of carbon and life as we know it. Do the values of these constants have reasons? Or are some of them simply what they are by pure chance?

My intuition has been that they have reasons. Our world is so intricate that I can't imagine that, when the universe was born, light simply took on a value of 3x10^8 m/s for its speed by chance. But until now, I couldn't understand what a reason might look like; what would possibly cause any fundamental constant to take on the value it does? I liked Giudice's talk because it helped me to understand how there could indeed be reasons behind such things.


Tuesday, 15 October 2013

Two theories of almost everything

The standard model of particle physics constitutes a huge development for modern physics, going a long way to fulfilling the physicist's ultimate dream, a 'Theory of Everything'. It describes all of the fundamental building blocks of matter known to exist, three of the four known forces that determine how they interact, and it even tells us how matter has mass at all. This last feat, of course, is achieved by the Higgs Boson.

The force that the standard model notoriously finds too challenging to describe is the very first force we learn about at school, gravity. Our best theory of gravity is Einstein's general relativity. Unifying the current standard model with general relativity would successfully create a Theory of Everything.

It seem rather simple then, doesn't it, to fulfil the physicist's dream? However, the current standard model and general relativity have proven horrendously difficult to unify, with attempts resulting in 'complete nonsense'. Physicists have turned their hopes onto other theories (including the commonly cited string theory), in the hope that these new routes will be more fruitful.

There, for now, the standard model remains: alongside Einstein's general relativity as one of two theories almost everything.

Tuesday, 8 October 2013

The Higgs boson and the Nobel prize

Congratulations to Francois Englert and Peter Higgs for their Nobel Prize achievement, and congratulations too to Robert Brout (post-humously), Tom Kibble, Gerald Guralnik, Richard Hagen, Philip Anderson, Jeffrey Goldstone and the thousands of technicians and experimentalists who have been part of the multi-decade long project to find the Higgs Boson at the LHC, CERN. 

As in almost any discovery, a lot of people have played a part in the discovery of the Higgs Boson. I've found it very satisfying to read about the story of the theoretical discovery that happened almost fifty years ago, the planning and construction of LHC and the very recent and momentous experimental confirmation; how lovely it is to recognise the small but hugely significant step that the human race has made in search of truth.

I wrote an article back in February, when the nominations for the 2013 Nobel prize winners came in; it talks a little about the history of the Higgs boson discovery and speculates upon who the winners might be. Read it here, if you're interested.

Thursday, 3 October 2013

It's a fascinating world

The world is a strange place, and the more I learn about it, the stranger I think it is. 

I've just finished a degree in Physics and Philosophy, and unfortunately have forgotten a great deal of the content I learnt (I'm not entirely sure what a capacitor is at this moment in time). However, I spent a lot of time studying the the bizarre behaviour of the world at the quantum level, and at the very least my enchantment with this has remained. The theory of quantum mechanics is both beautiful and mind-boggling: beautiful because it falls out so perfectly from the mathematics, and mind-boggling because it seems near to impossible to build a conclusive picture of what is actually going on. The maths simply does not fit our intuitions about the way things work.

As such, it was this particular area of science that captivated me during my degree. But of course there are many fascinating things to learn about in this world, from the physics of our universe at the smallest and the largest scales to the science behind man's inventions and the biology of the living world around us. Now that I'm no longer consigned to physics alone, I hope to read and learn about the vast number of fascinating things in this world, and, as I do, I will try to write about them here in a simple and accessible way, yet keeping true to the science.

Do comment and send me feedback!