Universe Today
This is Part 2 of a series on topological defects. Read Part 1.
But here’s the thing about these defects. They can’t just go away. They’re stuck.
If you’re old enough to remember, phones used to live on the wall or counter, and the handset was connected to the phone with a long windy cord. Everyone wanted extremely long cords, because of course you wanted to walk around your house doing stuff while still being on the phone. And the windy cords were designed to stretch to help accommodate that desire and then also return to a somewhat compact neat configuration when you were done.
This never, ever worked. The cords always tangled up on themselves and got themselves in knots. It’s just a fact of the ancient world that doesn’t exist anymore.
But once a cord got a knot in it, the only way to untangle it was to start at the end – the handset – and work your way back, passing the handset through any knots that appeared. And if you’re not old enough to remember when phone were like that, then I’m sure you can still appreciate the analogy of the general difficult of untying knots.
The universe can’t untie these knots. We call these defects “topological”, which means of or relating to topology, which means…shapes that locked in.
Let me give you some examples. Specifically, a mug of coffee. Forget the coffee – the important part is the mug. The mug has a handle. Now imagine the mug was made of clay, and you could squish and reshape the mug to your heart’s content, but you had to follow one and only one rule: there always had to be a whole. Think of all the wonderful shapes you could make! You could make a donut (one hole), a hula-hoop (one hole), but you couldn’t make a figure 8 (two holes) or a flat slab (no holes).
In the language of topology, all the possible shapes with one hole are the “same” – they have the same one-hole topology. And there are the two-holers, and no-holers, all sharing the same, but distinct, topologies.
The same goes for knots. Once a knot appears, you’ve got a different topology. It’s a different thing. A rope with a knot in it is fundamentally different than a rope without a knot in it. A universe with a defect in it is different than a universe without.
And the only way to get rid of the knot in a line is to reach the end of the line – you have to go outside the system entirely. There’s no way to get rid of the knot while staying inside the line. No matter how much you squish and pull and reshape the rope, you can never get rid of the knot.
Here’s a hint: there’s no end to the universe.
The quantum fields of the universe wrap themselves around the defects like the monopoles and strings. They get trapped. They get knotted up. But the fields also exist throughout all of time and space; they’re the fundamental building blocks of material reality. They have no end, no edge. There’s no quantum handset that you can grab to pull the fields through to untwist them. The knots are there, forever.
I mean, kind of. It IS possible to vanish a defect (which now get the promoted title of “topological defects”, because they are twists and knots in the vacuum fields of the universe). But it’s not easy.
The defects retain a memory of the very earliest universe. They exist in a kind of reality that the cosmos hasn’t experienced in over 13 billion years. They’re built different. And most importantly, they are concentrated points/threads of extremely high energy – the kinds of energies where the forces of nature are still united. The only way to untie the gordian knot is to pull the full alexander and slice the thing in half.
You have to melt the knot by reaching insanely high energies. Which…well, the universe ain’t what it used to be. It’s old, it’s cold, its low-energy. It just can’t do that kind of stuff anymore without pulling its back. You could blow up a supernova right next to a defect and it wouldn’t even flinch.
But the cosmos does have some tricks up its sleeve.
When it comes to strings, they can sometimes get caught up on themselves. They are, after all, intensely vibrating, wiggling things. And once a string crosses itself, the loop pinches itself off. Did I mention that vibrations can race up and down the spine of a cosmic string at the speed of light? Yeah, pretty cool. But when a string becomes a loop, those vibrations amplify each other, reaching the energies needed to melt the defect away like a good massage hitting a knot in your back, and the loop evaporates in a giant shower of radiation and gravitational waves.
Bye bye defect.
And monopoles? Well they have no extent whatsoever so it’s kind of hard for them to cross over on themselves. But despite that they can still outweigh a bacterium, which is wild to even think about, but that’s what we get for dealing with the early universe. But there aren’t just the monopoles, there are the anti-monopoles. And just like matter and antimatter, when monopoles and anti-monopoles meet, they go kablooey in a giant blast of radiation.
Okay so maybe these defects aren’t so permanent anyway. But when things go kablooey or twist up on themselves (going kablooey in the process), we should be able to see that, right? Astronomers are good at finding all the things that go bump in the night, so this should be the definitive evidence that we need that the universe does – or at least, did – have defects.
To be continued...
