Explaining the light mill

 

A crookes radiometer, as described in the text

Image source: Wikipedia

The light mill, also known as the Crookes radiometer, is a little curiosity that can be found in stores at science museums, or in the offices of physics professors. It consists of four vanes, each painted white on one side, and black on the other. The vanes are placed in a bulb, under partial vacuum. When you shine light on the radiometer, the vanes spin around, with the white sides facing forward (counter-clockwise in the above image). A demonstration is shown in the video below.

Supposedly, the Crookes radiometer is an educational tool, but I can’t for the life of me determine what lesson it’s supposed to teach. Because if you ask how it works, the correct explanation is far beyond the ability for most people to understand. I have a Ph.D. in physics, and I still couldn’t understand it! There are numerous internet sources that identify “thermal transpiration” as the correct explanation, but fail to explain what that means or why it happens. So instead I found explanations in scientific literature,1 and now I will share the explanation with you.

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In which I destroy marriage

Attentive readers may have noticed a while ago when I started referring to my robot boyfriend as my robot fiancé. As I’ve told various people, we’ve been cohabiting for years, so we’re functionally already married. But after graduating, getting legally married has become a good financial decision, for two reasons.

First, it lowers our taxes. The general principle is that marriage most benefits couples where one partner has much higher income than the other.1 Since I’ve been unemployed for at least the first half of 2018, marriage very likely benefits us this year.

Second, it lets me buy health insurance through my partner’s employer. This is fairly significant, because I regularly take medication for asthma, and this stuff is surprisingly expensive without insurance coverage. Obamacare guarantees that I at least have the option to buy healthcare, but as I found out when I looked at insurance plans last December, the options aren’t nearly as good as what you can get through employers or universities.

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Origami: Toroidal Cube

 

Toroidal cube

Toroidal Cube, a design by me

In case it’s not clear what’s going on in the photo, the model is in the shape of a cube, and we are looking at it directly onto one of the vertices.  However, the vertex has been cut out, and there is a triangular hole in its place.  There is also a triangular hole on the opposite end, so that you can see directly through the cube.  The triangles aren’t really triangles, but they look triangular from just the right perspective.

Today’s model was inspired by the regular toroid.  You may have heard of a torus, which is the shape of a donut, or a mug.  A toroidal polyhedron (aka a toroid) is a polyhedron which is also a torus.  A regular toroid is a toroidal polyhedron where each face has the same number of sides, and each vertex connects the same number of edges.

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Great classics

I consider myself very “anti-classics”. Which is to say that whenever someone praises the great “classics” of literature, such as Shakespeare, or Tolkien, or the Bible, I have a negative gut reaction. And it’s not so much that I think classics are bad, if only it were it so simple to explain. Some classics are good, some are bad–all as a matter of subjective preference–and to call something a “classic” is simply no recommendation in my eyes.

I have had difficulty translating these thoughts to ideas, and ideas to words. But it recently came up when I went with a group to see a small stage production of Hamlet, and we also had some conversations afterwards. So I’m sharing some of my thoughts on Hamlet and Shakespeare to illustrate my viewpoint.

To be clear, we all enjoyed the play. I hadn’t seen Hamlet since my high school put on a musical version of it themed on Queen, so it was nice to see it again, now with a more developed taste in literature. To the extent I complain about any aspects of the play, I have to say there’s a special appeal in having something to complain about, so it should not be taken as evidence of dislike.

By merit or by accident?

After we watched the play, someone in our group wondered aloud how Hamlet became so great a classic. In response, some of us speculated that it was a historical accident. These things happen! For example, the reason the Mona Lisa is so famous is because it was stolen (link is to video). For the two years it was missing, the media talked up the Mona Lisa as particularly great art–with textual descriptions rather than photos. After its recovery, its fame was self-perpetuating.

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An altruistic Prisoner’s Dilemma

This is a repost of an article I wrote in 2015, with a short postscript added.

Jeff Kaufman talks about an ethics trade that he sometimes does with a friend.

I have a friend who is vegan for animal welfare reasons: they don’t think animals should be raised for food or otherwise suffer for our benefit. On the other hand, they used to really enjoy eating cheese and miss it a lot now that they’re vegan. So we’ve started trading: sometimes I pass up meat I otherwise would have eaten, and in exchange they can have some cheese.

This is a win-win for the vegan, since they get to have some cheese, and there is no net harm to animal welfare.  It is not clear what’s in it for Jeff though, except for his idiosyncratic preference to have such trades.  I am not sure this is an interesting scenario by itself, since, in general, any trade is possible with sufficiently idiosyncratic preferences.

Therefore, I propose a similar scenario, which I’ll call the vegan/omnivore dilemma.

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Link Roundup: July 2018

The Lifespan of a Lie – Zimbardo’s Stanford Prison Experiment is one of the most famous experiments in psychology.  I knew it was questionable in methodology and ethics, but this exposé gathers all the details in a more shocking picture than I had imagined.  Zimbardo is a crook.  He repeatedly lied about key aspects of his experiment, persuaded subjects to also lie after the fact.  And when other researchers failed to replicate, he accused them of being frauds.  It is a disgrace that people in psychology still respect him.

I know that people still like to cite the Stanford Prison Experiment, because it “proves” something they already know to be true, but have you tried instead just… making assertions without proof, because at least then we’re honest?

The World’s Highest Paid Musicians vs Average Salaries – This is an infographic showing how long it takes for popular music artists to earn as much as people with other jobs make in a year.  It’s based on a Forbes list.  That just makes me think of when I asked my brother how much money he made being a rock star (although “star” is rather overstating it), and the answer was basically nothing.  So, this is your reminder that capitalism doesn’t produce anything remotely resembling “fair”.

What’s interesting to me, is that this is easily explainable.  I honestly don’t understand why CEOs get paid so much–it kinda seems like companies just overvalue CEOs, or there are principal-agent problems–but it’s easy to see why top artists get paid so much.  The popularity of music follows a power law distribution, so artist’s salaries follow that too.  I think it would be an interesting exercise to think up a more utopian system of art monetization.

Do algorithms reveal sexual orientation or just expose our stereotypes? – I’ve always found “gaydar” research to be disappointing, because it’s fixated on what you can determine from facial features alone.  In reality, when I can guess someone is queer, that’s based entirely on cultural markers.  So I would say “gaydar” research isn’t really about gaydars at all, and is about some loosely related concept that really ought to be given a different name.

This article I’m linking is a detailed critique of a “gaydar” study that built an AI that can purportedly guess people’s orientation from their faces.  The critique is that the AI is clearly basing its guesses on cultural markers and grooming habits.  And to me, the cultural differences are the more interesting ones.  I would not have guessed that same-sex attracted men in the US are more likely to wear glasses, or that they take selfies from higher angles.

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