WARNING: This entry has a LOT of background stuff in order to make the story a complete one. If you are patient, you will learn a lot... but dinner will be late.
The Higgs boson is sometimes called the God Particle (said with a deep, sonorous voice). That title irritates most physicists, who view it as a classic example of media hyperbole. The Higgs is the theoretical particle manifestation of the theoretical Higgs Field, which theoretically gives elementary particles mass. Theoretically, anyway. The graviton is something different, and like the Higgs has also never been seen, but is proposed by high-energy physicists to be the gauge boson - the force carrier - that conveys the force of the gravity field on all that mass.
You can quit here, but if you continue on you will be able to answer all your friends' questions about the Whichness of the Why.
Like... why is the Higgs being talked about so much in the media? Among other things, it has led to the multi-billion-dollar funding and construction of the largest and most technically sophisticated machine in the history of humankind: the Large Hadron Collider. The LHC is the source of worship of at least one atheist Harvard physics professor. It is a giant underground ring full of monster magnets, 27 kilometers (17 miles) in diameter, straddling the Swiss-French frontier.
But first, what's a hadron, anyway? A hadron is a heavy particle, made up of three quarks, the fundamental building blocks of the universe. A proton and a neutron are perhaps the best examples of a hadron. It's sort of like saying "siblings" instead of "brother," or "sister."
Uhhhh. Then what is a quark? For more than 30 years, the particle zoo called elementary particle physics has been more or less, well sort of, explained by something called the Standard Model. Let's see if this helps: twist electromagnetism with the Strong (nuclear) Force and tweak the Weak (nuclear) Force and you get... a lot of strangely-named particles and six different characteristics including mass, spin, "up-ness" and flavor. Among other things, gauge bosons are particles that carry or transmit the different forces between particles like hadrons.
Except mass and gravity. Since the 1960's, some of the sharpest minds on the planet have tried - and failed - to bring mass and gravity into the Standard Model. They wanted a Grand Unified Theory, or GUT for short. A Theory of Everything. String Theory is just one of many attempts at a GUT, and because it is mathematically elegant, it has seduced much of the physics community into its clutches. Just a few problems: String Theory is not testable, not falsifiable - so it's not even remotely scientific. It also has 10 to the 500th power (10^500) possible solutions; I could use it to predict the existence of Extreme Moosetracks Ice Cream. After the fact, of course.
I once took a graduate physics course called Group Theory and Quantum Mechanics; the idea was to predict still-unseen particles by building a sort of association matrix. An incomplete symmetry - an empty box in the matrix - might mean some particle physicists haven't seen yet. There were a lot of different particles in the high-energy zoo even at that time, and this approach eventually became Super Symmetry.
However, even with Super Symmetry no one has ever been able to figure out how to fit gravity and mass into all this. You know: the force and physical property that order the entire macro universe, cause galaxies to spin, bend light...
To explain the next part, we need to go back a century in history. Particle physics really got its start with Ernest Rutherford in 1911: he started out by stripping electrons off hydrogen atoms - leaving naked protons - and shooting a stream of these protons at a patch of gold foil. The first thing he noticed was that the protons were only very rarely deflected backwards. Mostly the beam passed through the foil with some electromagnetic repulsive bending. So: atoms and matter were mostly empty space. If one increases the energy of the beam, sometime protons would hit actual nuclei and stick - and new elements came into being, along with exotic particle fireworks in the original cloud chambers. The alchemist dream was finally realized: elements were converted to something else. The exotic particles that would go flying off would often last for just tiny fractions of a second and then break down into yet something else.
You can rivet the attention of a lot of over-sized children for a long time with a toy like this. But a tiny fraction of the great early experimental physics discoveries led to something with real-world consequences: a single bomb that could destroy an entire city.
Perhaps a residual benefit of having invented the nuclear bomb is that physicists can still wangle billions of dollars out of entire national governments to build bigger and better... proton smashers. Keeping in mind the basic Einstein equation of E=mc2 that equates matter with energy, the thinking goes like this: a bigger cyclotron, a bigger synchrotron, a bigger linear collider, a bigger Tevatron... and you can generate more energy when you shoot particles at each other. More energy means heavier particles pop up, however momentarily, in collisions. That generally means more new things, particles that hadn't been seen before.
Some more background: Let's talk a bit about electron-volts. This is the amount of energy gained by an electron moved across an electric potential difference of one volt. Technically, it's not even an SI unit, but it IS measurable, and equivalent to about 1.6 x 10^(-19) Joules. About 1 Quintillionth of a fly push-up. BTW: that ^(- symbolism means you move the decimal place 19 digits to the LEFT - in other words, you put a lot of 0's between the decimal and in front of that 1. That's pretty tiny; to put it in perspective, the power to run a 100 watt light bulb for one second is about 6 x 10^(+20) eV. That's six times ten to the twentieth power: moving the decimal point all the way back - and multiplying by another 40 besides.
But remember that matter and energy are interchangeable by that E=mc2 equation. In that case, the entire resting mass of the electron is equal to about half a million electron-volts, or 0.5 MeV, if converted to pure energy. The proton is heavier - more mass - so it's mass converted to pure energy is slightly under a giga-electron-volt, or GeV. The neutron is slightly heavier than the proton, so it comes out as slightly more than 1 GeV... or 1,008 MeV to be four-decimal-places precise. Maybe you see where this is headed by now.
As an aside, a photon of visible light has about 1.6 to 3.4 electron-volts, depending on its wavelength. And yes, if that photon has enough energy and hits something like a tiny electron, it will likely knock it around - even kick it out of its rest-state atomic shell. This is called ionization: there is a free electron floating around somewhere, and an atom or a molecule left with an excess of one positive charge. When the electron drops back down again to its rest state, it re-emits a photon of a precise wavelength that can be correlated with that particular atom. If you do it right, you can use this behavior to chemically analyze a molecule for its constituent atoms.
But heck: it all keeps coming back to gravity. It just won't fit in. Physicists have thought for at least TWO generations that gravity must just be another force - hey, it pulls masses together sort of like electromagnetism pulls two charged objects to each other (or pushes like charges away: SAYYYY... can there be an anti-gravity?). But where is the particle exchange that makes the force work between two masses? The gauge boson, the force carrier? For that matter, what gives rise to mass in the first place?
The Higgs would solve a big chunk of this problem... if it exists.
If you notice the very tiny numbers earlier, and then start thinking about the masses of galaxies with 100,000,000,000 suns in them... well, there is a lot out there that we know virtually nothing about. Intuitively, you might think that the Higgs boson must be something pretty bohonkin' huge. One rather mundane reason for this supposition is that it hasn't been found yet using smaller 'tron machines. So if it exists at all, it has to be out of reach of everything up until now except the LHC, right? That means a boson with a rather huge mass.
As I write this, no one has yet detected the Higgs boson. The science teams working at the LHC have been giving broad hints for a long time that they are seeing some "statistical" things that hint at its existence. However, that is a very, very long way from anything that anyone would call proof - and has a lot more to do with making sure that European governments don't suddenly pull all their LHC funding as the Euro goes down the tubes. These broad hints to the media are sort of like: your cousin knows a guy who heard from a neighbor that... Some theoretical studies have suggested that the Higgs might be in the energy range of 115 - 130 GeV. Not more, not less. For reference, 125 GeV is about 133 proton masses.
Hey, wait... the particle that gives rise to "mass" is ~133 times heavier than a proton?!??
If that sounds illogical, then give yourself three stars. And that isn't even HALF the problem.
Finally, we arrive at the recent history: Physicists gathered all the goodwill they could find, world-wide, and pooled enough tax-payer money (the U.S. Congress politely but firmly declined) to build the Large Hadron Collider at the CERN facility on the Switzerland-France border. This monster first came online in 2010. A lot of hope, and at least one atheist's faith, is pinned on that huge, spectacular machine.
History is being ignored again of course: every time something bigger is built to answer a question, new things pop up that need a bigger machine to answer... ad infinitem. Some people consider this an old con-game. In fact, the US Congress put a foot down in 1993, and cancelled the half-built American Superconducting Super Collider in Texas. It was a Texas-politician-boon-doggle with massive and growing cost over-runs, so this call was a no-brainer decision. This infuriated particle physicists, of course - but gave hope to most of the rest of the American science community that all their research funding wouldn't be gobbled up by a single gigantic foo-ball project.
So that's the story, right? I wish.
An article in a recent issue of Nature, by physicist John Ellis of the UK, titled "The Need for New Physics", makes these points:
- Whether or not the Higgs exists, there must be physics beyond the Standard Model:
- If the Higgs weighs in at less than 130 GeV, then all the calculations for the lowest energy state of the universe are totally wrong, totally unlike our current universe. A "mass-giving" particle that weighs 140 times the mass of a proton, really did seem a bit fishy, didn't it?
- What if the LHC results do NOT confirm a Higgs boson? Well, we could try to look at a particle heavier than 600 GeV... but that would take something bigger and far more expensive than the multi-billion-dollar LHC. We're talking about costs up in the range of another Iraq War (roughly calculated at $1 Trillion). But it's worse than even that: a heavier Higgs would require a host of new particles and particle interactions... and the interactions in the Standard Model become infinite at higher energies. The universe blows up. Since I'm writing this right now, that just can't be true.
Ellis has a number of even more arcane arguments, but the rather blunt bottom line is this:
Physicists don't know jack. We may think we're real smart, but we really know almost nothing.
If you got this far, you know more than The 99%. You deserve five gold stars on your forehead. And my thumb aches from teaching Jujitsu yesterday and today and hitting the space bar one too many times.