Today, my friends, following on from last week’s article, I am going to introduce to you, the most important particle you have never seen.

Now then, picture this. It’s the early 1960s, and physicists are feeling pretty good about themselves. They’re piecing together the ultimate instruction manual for the universe, a theory that would eventually become known as the Standard Model of Particle Physics.

There was, however, one teeny tiny problem. The maths insisted that many fundamental particles should have no mass whatsoever, and reality was very much in disagreement.

Electrons have mass. Quarks have mass. The particles responsible for nuclear reactions have mass. In fact, pretty much everything around you has mass, so, where does that mass come from?

The answer to that, as it turns out, lies in an invisible cosmic field that fills every corner of the universe, and a tiny particle called the Higgs boson.

Imagine the entire universe submerged in an invisible substance. Not a liquid, not a gas, but a field of invisible cosmic treacle, which physicists call the Higgs field. I’ve bolded that as it very much deserves it.

The field is absolutely everywhere. In your room, inside your body, between galaxies, and (slight pause for dramatic effect) in the emptiness of deep space.

You can never step outside it because it fills the entire cosmos, and some particles move through this field almost effortlessly, while others interact strongly with it and effectively become heavier. The greater the interaction, the greater the mass. And just like that, one of nature’s biggest mysteries begins to make sense.

Touching back on my last article, there is an analogy the physicists love because it captures the basic idea so perfectly. And that is the celebrity party analogy.

Imagine you’re in a crowded room and an ordinary, average Joe, enters. Nobody notices them. They walk straight across the room with ease, no interruptions, no one stopping them to chat, a bit sad really, I guess. Now imagine a famous movie star walks in and people start gathering around them, wanting selfies, autographs and conversation. Suddenly, for that one individual, moving across the room becomes that much harder.

In this analogy, the crowd is the Higgs field, the celebrity is a particle with lots of mass, and the unnoticed person is a light particle. The more interaction there is with the crowd, the more “massive” the particle appears. Although it isn’t a perfect comparison, it is a great way to visualise a very strange piece of physics.

If you were to travel back nearly 14 billion years, before mass existed, to immediately after the Big Bang, the universe was warm, it was very warm, in fact, it  was unimaginably hot. So unimaginably hot that the Higgs field behaved very differently.

Particles zipped around at light speed. Mass as we know it didn’t really exist. Then the universe cooled and a cosmic phase change occurred.

The Higgs field “switched on” and settled into the state we observe today as suddenly  particles gained mass, and the universe changed forever.

If it hadn’t been for that moment atoms would never have formed, chemistry would never have happened. Stars would never have ignited, planets would have never existed, and life, itself, would have been impossible. And in many ways, this was the moment the universe became recognisable.

So, that leads us to a question. Just what exactly is the Higgs Boson? And the answer to that question, dear readers, is when things start to really get interesting, as the Higgs boson is not the field itself. It’s more like a ripple in the field.

Analogy time again! Think of a pond. The water is the field and the ripple is the particle. The Higgs boson is simply evidence that the Higgs field exists. Physicists had spent decades looking for that ripple because finding it would prove the field was real.

No Higgs boson? No Higgs field.

No Higgs field? Back to the drawing board, I’m afraid.

Finding the Higgs boson became the ultimate scientific treasure hunt, as it wasn’t easy. In fact, it became one of the most difficult experiments ever attempted, as the particle is extremely rare, very heavy, incredibly unstable, and most annoyingly, it’s gone almost instantly after it’s created. To find it, scientists needed a machine capable of recreating conditions that existed fractions of a second after the Big Bang.

This is when the Large Hadron Collider entered the scene. Buried beneath the French-Swiss border near Geneva is the largest machine humanity has ever built. The LHC is a gigantic 27-kilometre ring that accelerates protons to almost the speed of light.

Scientists smash these particles together billions of times every second, and where most collisions create nothing unusual, every now and then a Higgs boson briefly appears, and then vanishes almost immediately. The challenge is spotting the clues it leaves behind. A bit like reconstructing a firework after seeing only the sparks.

On 4 July 2012, physics changed for ever, as  scientists around the world held their breath, researchers at CERN announced that they had discovered a new particle, and two independent experiments, ATLAS and CMS had detected exactly the sort of particle predicted nearly fifty years earlier. The missing piece of the Standard Model had finally been found.

Many physicists were emotional. Some cried, while others sat in stunned silence. One scientist in the room that day had spent almost his entire career waiting for that announcement, and his name was Peter Higgs.

The theory behind the Higgs mechanism had been proposed way back in 1964, and at the time it was nothing more than an elegant mathematical solution. For almost half a century there was no direct evidence that it was correct.

Then the LHC confirmed it.

In 2013, the Nobel Prize in Physics was awarded to Peter Higgs and Francois Englert, for helping develop the theory that eventually led to the discovery. It’s one of those extremely rare occasions in science where an idea survived decades of scrutiny and turned out to be almost exactly right.

You’ve probably heard the Higgs boson referred to as The God Particle. A nickname that practically all physicists hate. Although it sounds mysterious and spiritual, the reality behind the nickname is much more amusing. Physicist Leon Lederman reportedly wanted to call it The Goddamn Particle because it was proving so difficult to find. Publishers thought that title might be a little too spicy for bookstores and so they shortened it, and in an instant a nickname was born, which, unfortunately, stuck!

One of the biggest surprises was that the Higgs doesn’t give everything mass. The Higgs field gives mass to fundamental particles such as electrons, quarks, W bosons, and Z bosons, however, most of the mass inside your body actually comes from somewhere else.

Take a proton for example, the quarks inside it only contribute a small fraction of its total mass. The majority comes from the immense energy of the strong nuclear force binding those quarks together.

And in a strange twist, Einstein’s famous equation, E = mc², means energy itself contributes mass. So while the Higgs is essential, it isn’t responsible for all the weight in the universe.

This raises another obvious question. Could the Higgs explain dark matter? This question takes into the realm of modern mysteries. Scientists know that ordinary matter accounts for only a small percentage of the universe. The rest appears to be dark matter and dark energy (article on this coming soon).

The thing is, nobody really knows what dark matter is. Some theories suggest the Higgs field could act as a bridge between ordinary particles and an unseen hidden world, and if that’s true, the Higgs boson may eventually help reveal one of the biggest secrets in cosmology.

Are you ready for something truly weird? There’s a slightly terrifying instance to the Higgs theory.

Current measurements hint that our universe may not occupy the absolute lowest-energy state possible, something physicists call the metastable vacuum.

Analogy time! Think of a ball sitting in a small valley when an even deeper valley exists somewhere else. It may be stable for now, but theoretically it could drop to a lower state, and if that were ever to happen, a bubble of new physics would spread across the universe at light speed, rewriting the laws of nature as it went.

The good news?

Calculations suggest this is so unlikely that the universe will probably survive vastly longer than the lifetime of all the stars combined. So, I really wouldn’t lose any sleep over it, although I think I may pin that as the premise for a future novel.

And there’s another question. Is there more than one Higgs? And the answer to that question is…

Possibly.

The particle discovered in 2012 may be only the beginning as some theories predict multiple Higgs bosons, charged Higgs particles, and even entire families of Higgs-like particles.

Finding even one extra Higgs particle would be a scientific earthquake as it would instantly prove that the Standard Model is incomplete, and there are many physicists who believe that that is exactly what future experiments may reveal.

Even after one of the greatest discoveries ever made, huge mysteries still remain that keep a great many physicists awake (over enthusiastic amateurs too).

Why is the Higgs boson’s mass about 125 GeV? Why is the top quark enormously heavier than the electron? Is the Higgs truly fundamental? Is it connected to dark matter? And the answer to these questions is…

Nobody knows.

There is another question, could the Higgs reveal entirely new laws of physics? And the answer to that one is…

Possibly.

The discovery of the Higgs may have solved one problem but opened many more.

So, why does the Higgs boson matter?

The Higgs boson isn’t just another particle. It’s proof that empty space isn’t empty. It revealed that the vacuum of space possesses hidden structure that shapes reality itself. The stars overhead, the atoms in your body and the world around you all depend on an invisible field that quietly fills the universe.

That’s why the discovery of the Higgs boson ranks alongside the greatest scientific achievements of all time, as it showed us that the fabric of reality is stranger, richer and more beautiful than anyone imagined.

And perhaps most remarkably of all, it revealed that everything you have ever touched owes its existence to an invisible field that stretches endlessly across the cosmos, silently giving substance to the universe itself.

And that, is another reason of many that I love physics so much.