Quantum field theory: "An unholy crossbreed between quantum physics in a bad mood and every button you never push on a calculator"
Quantum field theory doesn’t get much coverage in popular science and if you open any textbook on the subject you’ll see why.
Humanity is a bit like a puppy. We’ve spent the last few millennia bounding around the planet eager to explore, but our lack of care has made a terrible mess. If an alien race were to put us on trial for our crimes (like Q does in Star Trek: The Next Generation) we would have to stick our tails between our legs and acknowledge that we’ve screwed up.
But could we offer anything in our favour? Is there something we could present to these alien overlords which would prove that despite our failings, humanity is moving in the right direction? I believe we would need to show them two things. First, the collected cinematic works of Jason Statham starting with The Meg (the one where he fights a dinosaur shark). Second, we need to present our understanding of quantum field theory - the most advanced scientific discovery we have ever made.
Read more about quantum physics:
- Dead and alive: why it's time to rethink quantum physics
- Quantum theory: the weird world of teleportation, tardigrades and entanglement
- What is Schrödinger's Cat?
Quantum field theory doesn’t get much coverage in popular science and if you open any textbook on the subject you’ll see why. It looks like an unholy crossbreed between quantum physics in a bad mood and every button you never push on a calculator. The idea of summarising it in 1,500 words or less for this article sounded daunting at first (it took a whole chapter to cover it in my recent book) but then again if I really did have to present it to a jury of aliens I wouldn’t have a choice.
Therefore, your honour, I request that you give me five minutes of your intergalactic attention. My presentation may not feature Jason Statham roundhouse kicking a shark in the eyeball, but I am going to try and justify the continued existence of the human race. Here goes...
Any object can be described in terms of its constituent particles and any event can be described in terms of how those particles interact. The more we know about how particles behave, the more phenomena we can explain. That’s the goal of quantum physics; to learn all the fundamental laws of particles and use them to understand everything.
But things get very complicated very quickly because each type of particle has its own set of laws. The quantum rules governing nuclear explosions are different to the quantum rules governing mutations of DNA so there isn’t just one version of quantum physics, there are several.
Quantum field theory is an attempt to unite these different sets of laws and formulate a single framework that accounts for everything in one go, rather than having multiple flavours of the same theory.
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It’s a lofty ambition, but what we need to point out to the aliens judging us is that we have actually been successful in doing it. We really have discovered a unifying principle which seems to account for the whole of quantum physics and all that remains is to extrapolate the principle to different scenarios.
Presumably of course, the aliens listening to our plea will have already discovered quantum field theory for themselves. We therefore need to prove that we genuinely know what the central idea states, and this is where things get strange (aka worth studying).
When we do normal physics we traditionally visualise particles as little balls zipping around in empty space. It’s a useful way of picturing the Universe but it doesn’t explain why different types of particle follow different sets of laws. Quantum field theory solves the conundrum by making a radical change to the picture: scrap the idea of particles altogether because they don’t really exist.
Picture a tornado moving through the air. Although we think of it as a self-contained object we know it is not truly a ‘thing’ in its own right. It is just a fluctuation, whipped together from the surrounding air. The same can be said for a wave undulating across the surface of the ocean. It looks like a distinct entity moving independently of the placid water around it, but we know that the wave and its surroundings are really made from the same stuff. This, according to quantum field theory, is how we need to understand particles.
One of the greatest achievements of human civilisation?
In quantum field theory, empty space is not genuinely empty. It is filled with what physicists call ‘fields’ - fluid-like substances which extend in all directions. Just like the water in our ocean analogy or the air in our tornado analogy, these fields are typically dormant, but if they get agitated, pockets of turbulence can bubble into existence and move around as if they were separate objects. We call these little clots of energy appearing in the field ‘quanta’ or, if you prefer, particles.
The particles we use in normal physics to describe the world are not really lumps of stuff moving through space, they are miniature tornadoes formed from the all-pervading fields which flood our Universe. Particles are, in a sense, an illusion.
You might find the idea that you aren’t really made of anything unsettling, but quantum field theory has made a string of knockout predictions which make it hard to dismiss. The existence of the Higgs boson for one. The existence of antimatter and neutrinos for another. Not to mention predicting the so-called ‘fine structure constant’ (a measure of how well electrons interact with light) to the highest number of decimal places ever recorded.
Quantum field theory has also enabled us to bring the different versions of quantum physics under one roof and almost anything we want to study now, from food chemistry to flame-throwers, can be understood with the same starting assumption: the Universe is a collection of overlapping fields and what we think of as matter is just three-dimensional bumps forming in these fields.
We have not figured out all the details yet, nor have we found a way of using it to account for gravity, but quantum field theory is the deepest we have dug into the fabric of reality and it has the capacity to explain everything we experience.
So, if it please the cosmic court, I present to you the most advanced breakthrough the human race has made to date. Yes, we are baking our atmosphere, beheading our rainforests and drowning our oceans in plastic, but we are not a lost cause.
Considering we only started doing proper science a few centuries ago and have already uncovered the single underlying principle of all physical phenomena in the Universe, I think that is sufficient evidence to show that we have potential.
If that is still not enough however, you can still catch Jason Statham starring in the action blockbuster Fast and Furious: Hobbes and Shaw, only in cinemas.
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