Beyond the boundaries of the natural elements may lie a whole new form of matter without protons or neutrons: quark matter. [2 of 2]
In Part 1 I wrote about the island of stability, that theoretical point of supermassive but (relatively) stable elements beyond the periodic table we know. But there’s another theoretical point even further out that could be much much larger. It’s also a whole lot messier. To get there, we need to move beyond protons and neutrons and into much stranger territory.
In exploring this territory, I debated whether to begin with James Joyce or The Simpsons. In keeping with this website’s classy and sophisticated tone, I opted for the Simpsons.
The very first appearance of the Simpsons was in a series of shorts made for The Tracey Ullman Show, starting in 1987. The very first such short involves the family’s bedtime, and the very start of that very first short is a conversation between Homer and Bart:
Homer: Well, good night son.Good Night
Bart: Er, Dad?
Bart: What is the mind? Is it just a system of impulses, or is it something tangible?
Homer: Relax! What is mind? No matter. What is matter? Never mind.
Homer and Bart were a lot smarter back then, no? Anyway, that last question – “what is matter?” – has been the subject of scientific and philosophical pursuit for millennia. It wasn’t until the very late 18th century CE that we began to really get into the fundamental nature of matter. Short answer, pretty much all the observable matter in the universe is made of atoms. And those atoms are made of protons and neutrons orbited by electrons. The different combinations of these particles form the elements we know and love.
Our discovery of protons, neutrons, and electrons was enough to trigger some pretty astounding science and technology (modern chemistry, materials science, atom bombs…), but it wasn’t the end of the story. In 1964 a couple of physicists theorized that protons and neutrons were themselves composed of something even more elementary: quarks.
(This is where James Joyce comes in, by the way. The name “quark” comes from his influential and impenetrable book Finnegans Wake: “Three quarks for Muster Mark!”)
Quarks combine together to form protons, neutrons, and other particles. Quarks come in different varieties – poetically called flavours – and different combinations of quarks determine the nature of the particle they create. A proton, for example, is made of two up quarks and one down quark. A neutron is one up quark and two down quarks. They are held together by another elementary particle called a gluon.
Still with me? Going back to Part 1, I talked about the fact that elements above a certain size are inherently unstable and tend to decay – with the possible exception of an island of stability beyond the current reaches of the periodic table. And that’s inevitable for matter made of protons and neutrons. But what if there were a new type of matter?
Quark matter, like regular matter, is full of quarks. But rather than being bound up in protons and neutrons, in this matter the quarks flow freely on their own: up quarks and down quarks and gluons too finally able to kick around independently. We managed to make one variety of this matter for the first time in 2000: a quark-gluon plasma. Its creation involved the hottest temperatures ever produced on Earth.
The existence of quark matter means that elements could be much much heavier than our current heavyweights and yet remain surprisingly stable. Theoretically, there could be a lot of such elements. Not just an island of supermassive stability, but a whole continent’s worth. This possibility was proposed in a paper published in 2018 (fourth link below), which also coined the phrase “continent of stability.” It remains tantalizingly theoretical at this stage, but future experiments (such as those in the Large Hadron Collider) may make it a reality.