My monthly astrophysical column written for the Astronomical Society of Southern Africa.
“All truth passes through three phases. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as self-evident.” – Arthur Schopenhauer, German philosopher, 1788 – 1860
The media are awash with rumour, speculation, and no small measure of excitement. No doubt the thirteen million eager sycophants who bought and applauded Stephen Hawking’s monumental best-seller, A Brief History of Time, are leaning forward in their armchairs in rapt expectation—the shady halls of journalism are experiencing a feeding frenzy, devouring the scraps cast out by CERN and regurgitating them with thrilling headlines: The God Particle has been found! It must have been. As the cost of the Large Hadron Collider spirals upwards towards the twenty-billion-dollar mark, the world of armchair scientists prepares a fete of celebration not seen since Sir Arthur Eddington announced that he had indeed found confirmation of General Relativity Theory in the solar eclipse of 1919. So what’s all the fuss about?
One of the great remaining challenges in theoretical physics is finding a verifiable quantum theory of gravity, in other words, finally uniting Quantum Mechanics with General Relativity to give the world the much-vaunted Theory of Everything. What stands in the way of progress towards such an achievement is one tiny, ever-elusive particle called the Higgs Boson.
University of Edinburgh’s theoretical physicist Peter Higgs is an affable, well-meaning chap. I recall reading a press interview with him a few years back, in which he stated quite clearly that he did not believe that the particle that bears his name actually exists, and that he did not expect that it would ever be found. Be that as it may, it was Dr Higgs who in 1964 independently gave us one version of a theoretical construct called Spontaneous Symmetry Breaking. The Standard Model of Particle Physics explains force by means of intermediary particles known as force carriers. These quantum mediators “carry” the force from the object effecting the force to the object being affected by the force. However, Spontaneous Symmetry Breaking has an abiding, serious flaw: It could not explain the means by which an object obtains mass, and consequently, has grave difficulty with gravitation. That’s where Dr Higgs came in. Based upon the prior assumption that the Universe indeed had a beginning in time, Dr Higgs theorised that particles in their primordial state are massless, and acquire mass almost immediately after birth by interaction with a hypothetical quantum energy field that permeates all of space (the Higgs field). He devised a mathematical mechanism whereby vector bosons (a boson is a class of subatomic particle associated with force) can obtain rest mass without violating other constraints embedded in the Standard Model.
The key to Higgs’ theory was the Standard Model’s missing link, an ephemeral unit of energy that took the title “Higgs Boson”. Because it was tantalisingly close to sealing the Theory of Everything, the popular media soon gave it a catchy name, the God Particle. Although the Large Hadron Collider’s predecessor, Fermilab’s Tevatron Collider (which shut down in 2011) was capable of more than enough collision energy to reveal the Higgs boson, particle physicists wanted a much bigger toy to play with, and that’s how we came to enjoy the 27 km loop 100 metres beneath the French-Swiss countryside known as the Large Hadron Collider.
The Standard Model strictly requires for mathematical consistency that any mechanism that would impart mass to elementary particles should become visible in particle interactions above a certain threshold, which both Tevatron and the LHC are designed to achieve. Clearly, the Higgs Boson needs to be seen, and definitely should be seen if the model’s correct, but there’s a problem. It’s quite impossible to see it.
Fundamental particles are strange creatures. They require a bespoke mathematical language and a unique scientific model just so that they can be described. They might just as well be aliens, so weird are they. One of the properties they are awarded by those painting the theoretical landscape is that they exist for unimaginably brief moments of time—they come into existence, and almost instantly disappear again. For the Higgs Boson, the lifespan according to my calculations is around 1 zeptosecond. What’s that, you may well ask? It’s one sextillionth of a second. That’s one second divided by 10 to the power 21. In other words, one second over 1 followed by 21 zeroes. A billion times a trillion; we’re talking about a billion-trillionth of a second. Get it? Thought so…
Okay, that’s how long it lives for. How far does it travel during its lifetime? From birth to death, how long a trail would it leave on a photograph of the event? We use Planck’s constant and Heisenberg’s Uncertainty Principle to calculate that a particle with this sort of energy (we have to best-guess the mass because it is not predicted by the Standard Model) will travel around 100 fermis before it disappears. So what’s a fermi? It’s a femtometre. That is one trillionth of a millimetre. It equates to about one third of the diameter of an electron. And an electron, you will recall, is less than a thousandth of the diameter of the nucleus of an atom. Still with me? Good.
Right, clearly we cannot see or detect things that small or that temporary. I shouldn’t think anyone of sound mind would argue that point. However, the Standard Model does predict some scenarios that could be read as a signature of Higgs boson decay. For example, in a proton-proton collision of sufficient energy, they would hypothetically decay immediately to form two hadrons and two electrons which escape laterally, and these would be visible as lines on the plate. How does this indicate the presence of the Higgs boson? Well, that’s a bit tricky, but the model does say that it does, and who are we to argue? Higgs’ 1964 paper showed mathematically that only a particle with mass can decay, that particles are born massless and acquire mass by the intervention of a particular boson, and therefore, by simple deduction, if I cup my hands by lacing my fingers together, and put my foot into it, I’d be able to give myself a leg-up to see into the top cupboard. If you get my drift…
In other words, if the LHC detectors were to see some lines like those suggested, the CERN team could in principle claim to have discovered the Higgs boson. The fact that I would personally be highly sceptical of such claims doesn’t mean a row of beans. There’s a vast machine rolling down this particular hill (excuse the pun), and I’m not ever going to slow it down, let alone stop it. Five leading theoretical physicists, including Peter Higgs himself, have been invited to a press conference in Switzerland in two days’ time, and the expectation is that the “discovery” will be announced there. Will God be replaced by a particle in popular opinion? I doubt it. But the ideological divide between believers and atheists (essentially also believers, since non-existence cannot be known) is becoming more pronounced with each passing day, and somewhere between the two extremes are reasonable people, trying to make sense of it all. Both camps claim privileged vision, and describe their clairvoyance by talking in tongues. What seems to be lacking, in my view, is a decent dose of humility.
We shall have to scrutinise these pronouncements very carefully. After all, it will affect us long-suffering astronomers in ways that we have yet to realise, and place yet another incomprehensible constraint on the way we are being told to view the cosmos. Atheists will beat their chests and crow in their usual annoying way, and believers will no doubt declare that the Bible predicted it; that leaves you and me somewhat bemused with our little telescopes and red-filtered torches and Norton Star Atlases as we try to wrap our heads around big-buck politics.