Is the Universe Defective? Part 2: The Persistence of Memory

This is Part 2 of a series on topological defects.

Read Part1. 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.