What are topological defects?

This is a repost of an article I wrote in 2013, back when I was willing to take the time to explain physics stuff, and generate lots of images too.

Donut and Coffee
(image source)

It’s often said that topology is the branch of mathematics where they can’t tell the difference between a donut and a coffee mug. They each have a single hole (the mug’s handle and the donut hole), and that’s all that matters. If I may overanalyze this joke, the point seems to be that topology is so disconnected from our everyday experience. How is this useful?

I wish to explain one particular use of topology in physics: topological defects.

A topological defect is a sort of knot that exists in the microscopic structure of a material.* You can move the knot around from atom to atom, but you can’t untie it. We’ll get into how that works soon enough.

*Material is a vague term for “stuff”. Later I’ll discuss a few different materials including magnets, liquid crystals, and superconductors [Read more…]

Five awful things about “God’s not Dead”

This is a repost of an article I wrote in 2014.  I thought it might be relevant, given that God’s Not Dead now has a sequel.

I saw God’s Not Dead, a Christian film that appears to be based on that absurd chain e-mail about the brave Christian student who faces down an atheist professor.  This movie got a 16/100 on metacritic, but still ended up a big box office success.  If you want to know what happens in it without watching it, I recommend this synopsis.

In the world of God’s Not Dead, atheists are horrible people who mock their girlfriends in public, abandon people close to them when they’re dying, and secretly hate god.  The movie joyously depicts atheists dying by cancer or car accidents, and gloats over their last minute conversions.  Also, all atheist arguments are arguments from authority or assertion (oddly, so are the Christian arguments).

But a lot of that has already been said.  So here I present five things that were awful or bizarre about God’s Not Dead that had nothing to do with atheism.

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The Extremely Simple Model of Orientation

I’m trying a monthly feature where I repost things from my archives.  This one is from 2015, and is very silly.  It’s also a great example of talking about asexuality without talking about it.  A preoccupation with modeling orientation is flamingly ace.

When it comes to models, simplicity is a value. The point of a model is not to tell you everything, but to isolate the information that you actually want to know. When people try to model human sexuality, they often undervalue simplicity, leading to such misguided attempts as the following:

Transcript: an equation for W, the amplitude of a quantum transition, including parts from quantum mechanics, spacetime, gravity, other forces, matter, and Higgs.
The Universal Equation Model of Orientation (TUEMO). Image borrowed from Sean Carroll.

Proponents of this model argue that they are making simplifications, and far too many. For instance, they already graciously ignore quantum gravity, under the assumption that black holes aren’t involved in most human relationships. But I say it still doesn’t go far enough. I propose a bolder simplification…

[Read more…]