[lamchopz]

The term “particle”, coined by the wise ancient Greeks, literally means “an indestructible identity” (but don’t take it the wrong way, modern Greeks haven’t lost a single bit of their hereditary wisdom). The word itself gradually lost its meaning with the discovery of electrons which directly suggested that there were more fundamental identities. The electrons were later known to be negatively charged but the atoms in which the electrons were housed were usually neutral. Physicists logically inferred that the atom also contained positively charged materials but had no idea how they were all arranged. The first acceptable model was the Plum Pudding model of the atom which proposed that electrons were immersed in positively charged materials, much like a pudding (yes, physicists are very imaginative in naming their theories). Rutherford kicked this model off the table once and for all with his famous scattering experiment. It then became a matter of fact that the atom was mostly empty with a tiny positively charged nucleus at the centre and the electrons on its periphery. This encouraged Bohr to formulate his model of the atom which is the standard picture in any high school science class: a nucleus with electrons revolving around it in well defined orbits. Like Planck in a sense (but not quite), Bohr had to make several post priori assumptions to ensure that his model worked. It did work, for a hydrogen atom but proved to be problematic for larger molecules (as an aside, Bohr’s model is still constantly used in cases where heavy atoms can be approximated to a hydrogen atom). We now know that the electrons don’t orbit the nucleus like planets orbit the sun but rather, they assume different shapes (clouds) which are directly related to the highest probability of finding them at a given time. The theory is called hybridisation theory and has been the standard model of the atomic electron configuration. If you now look at the science class’s picture of the atom, it is actually not wrong: the orbits depicted do not explicitly relate to the apparent paths of the electrons but rather they serve as pictorial representations of the electrons’ positions at any given time.

Then there was the question whether the nucleus was really a fundamental particle like the electron. This is when modern particle physics widened its wings and soared to a new height. Particle collision is achieved in a monstrous set of equipment called a collider whose one major feature is an accelerator. The accelerator underwent transformations from the linear form (linac or linear accelerator) to the powerful synchrotron. Upon colliding protons and neutrons which were thought to be basic constituents of the nucleus, we observed many other unknown particles spitting out. The logic here is that if protons and neutrons (generally called nucleons) were fundamental (that is, indestructible) particles, the collision would return the same protons and neutrons. The fact that a myriad of different particles were produced suggested that the nucleons were not what we believed. Another interesting fact was that the new particles exhibited the known properties of the nucleons! At this stage, there are two questions that you might ask: how did we detect the new particles and how did we work out what lay inside the nucleons?

To answer the first question, we need to invoke Einstein’s E = mc^2 but with a little variation: m = E/c^2. Algebraically, the two equations are of the same kind but physically, they mean totally different things. E = mc^2 implies that an enormous amount of energy can be obtained from a small mass (the idea behind nuclear bomb) whereas m = E/c^2 refers to mass arising from energy. Indeed, energy, not mass, is a more fundamental property of a system. As such, when we analyse the energy pattern produced by the collider, a distinct peak will correspond to a particle according to m = E/c^2.

For the second question, it is rather a very elegant discovery. It is elegant because the constituents of the nucleons and similar particles, now widely known as quarks, were theoretically predicted by the established group theory before being observed and confirmed experimentally! This is reminiscent of the antiparticles whose existence was inferred from Dirac’s equations and experimentally verified.

The introduction of quarks revolutionised the field of particle physics. Not only did we solve the mystery of the ambiguous “nuclear force” which was then renamed to “strong interaction” but we are also able to construct an expansive framework where the four fundamental forces of Nature and their appropriate mechanisms slowly came to light.

It is not the end of the journey. We are still very far from “knowing it all”. While the weak force partly explains the fact that the current universe is made up principally of up and down quarks, it does not fully account for this observation as well as elucidate on where the antimatters disappeared to even though in the beginning, according to the Big Bang theory, an equal amount of matter and antimatter were produced. The Standard Model, which is the greatest model to date, successfully incorporating the strong, weak and electromagnetic interactions and allowing seamless and effortless formulations based on observations (unlike in the past when one sometimes had to use clever guesswork, like Planck and his equation for Black Body Radiation), is still unsuccessful in integrating the gravitational force into its structure. There exists a need for a larger, better theory in the quest of unifying the known forces. The Unified Field Theories are a strong candidate but it is still imperfect. If we then speculate further theories, one of which is the low-energy supersymmetry, Unified Field Theories instantly becomes a perfect model.

Preceding the Large Hadron Collider, there was the Large Electron Positron (LEP) Collider at CERN. The LEP experiment was the most extensive and impressive international collaboration ever achieved: more than a decade of work just to determine the one single quantity, the mass of the W boson. Perhaps hearing my lecturer, who was involved in the experiment itself, retell the achievement in its grand details was one of the most inspirational experiences in my entire life.

So we look forward, with the knowledge that our current theories, immensely successful yet conspicuously limited, are in need of expansion, extrapolation and solidification. The Large Hadron Collider (LHC) will do just that. Owing to our refined understanding of accelerators, we are able to attempt this ambitious experiment right here and now and because of the enormity of the modern theories that were beautifully devised but still need to be verified, such as the Higgs’ mechanism and its associated Higgs’ bosons which are speculated to give rise to mass (and consequently matter as we know it), the LHC will not only carry just two protons heading for collision but also our ambition, expectation and exultation in hope of finding, for the first time, the new physics which we’ve been consciously waiting for.

That’s science. The way it should be.

P.S.: Most likely, when I mention LHC, people tend to think of the movie Angels and Demons and the one kilogram of antimatter. While the internal view of the LHC was accurately filmed, the rest was pretty much fictitious. The controller room is actually situated above ground with a view into the outer landscape but the more pressing affirmation I must make is that the LHC, even if running at its full intended capacity (14TeV or 14 tera-electronvolts), will not produce even some hundred grams of antimatter. So rest assured, DoomsDay won’t come.