I read popular physics: The cosmic crisis

Someone went and got me a subscription to Scientific American, so for the past few months I’ve been covering physics articles, now with the benefit of a PhD. Perhaps it’s a way to keep in touch with my physics roots as my career has moved on to other things.

In this month’s issue, the cover article is “A Cosmic Crisis“, about a discrepancy between two measurements of the age of the universe.

Funny thing, there’s always a letter from the editor in chief where he introduces all the major articles, and here he contrasts the “cosmic crisis” with another ongoing crisis, that thing between US and Iran. Yep, this sure is an article that was written last month! FWIW, I could do with some reading that has nothing to do with COVID-19.

I thought I’d review the article in approximately the order in which I read it: pretty pictures first, walls of text last if at all. For serious, this is the correct way to read a science article, I can say that as a person with a PhD.

[Read more…]

I read popular physics: Giant Atoms

Someone went and got me a subscription to Scientific American. So I’ve been looking at these popular physics articles, marveling at what they look like post-PhD. I will continue doing this until I get bored.

Today, I will look at an article in the February issue, titled “Giant Atoms”, by Charlie Wood. It’s a short article about the MAGIS-100 experiment, which I was previously unaware of.

I got two main points from the article:

  • The MAGIS-100 experiment drops atoms down a 100 meter vacuum tube, creating “room-length” atom waves.
  • The experiment will eventually be sensitive to gravitational waves, and new forces that interact with dark matter.

[Read more…]

I read about the triple slit experiment

Someone went and got me a subscription to Scientific American, which is nice. Haven’t read one of those since before my PhD. In theory, I should be able to understand it a lot better. In practice, popular articles often omit crucial details or use “creative” explanations that would confuse most professionals.

So I went straight to the physics section and found an article titled “The Triple Slit Experiment” by Urbasi Sinha. Already this has me a bit confused. What’s so special about three slits? And why stop at 3? You can just have slits repeating indefinitely. It’s called a diffraction grating, and I had one when I was a kid (from this book).

Lightbulb as seen through a diffraction grating. A rainbow ring appears around it.

Diffraction gratings turn everything to rainbows, and are great toys. Credit: Wikimedia Commons

So I looked through the article to see what was going on. The article makes three main points:

[Read more…]

The physics of Dominion

For this month’s repost, I’m publishing up an article I wrote in explanation of a programming project in 2018.  In theory you could find it on Github, but to maintain a layer of pseudonymity I’m not linking it directly.  A few minor revisions have been made to adapt to the audience.

Introduction

The goal of this project is to create Markov Chain simulations showing that the card game Dominion contains phase transitions, much like the physical phase transition between liquid and solid.

Dominion is a popular card game created in 2008. In Dominion, each player has their own deck, and they add/remove cards from their deck over the course of the game. Each game has a unique set of cards available to be added to players’ decks, making the optimal strategy in each game different. However, there are two archetypical strategies, based on two fundamentally different decks. The “Big Money” deck makes the best of the 5 cards drawn each turn. The “Engine” deck includes cards that draw more cards, and tries to draw itself in its entirety each turn.

Because of my background in physics, I recognized that the line between “Big Money” and “Engine” strategies is a phase transition. More specifically, it’s a one-dimensional percolative transition. That explains why there is such a strong dichotomy between the two strategies over a wide range of conditions.

[Read more…]

Conjugate variables, in thermodynamics and elsewhere

When I wrote an explanation of cap and trade, I had a strong temptation to make a physics analogy, to an idea in thermodynamics. The trouble is nobody would understand the analogy, and I would be obliged to explain the physics instead of the economics. Well I’d still like to explain the physics, but in a separate article.

There are certain thermodynamic quantities that are considered to be paired with one another. For example, pressure and volume, or temperature and entropy. These pairs are called thermodynamic conjugate variables.

The concept of conjugate variables can be challenging for physics students to understand because the examples we use are unintuitive. The connection between pressure and volume is unclear, and most people don’t wholly understand what temperature or entropy even are. Therefore, I’d like to use a more down-to-earth example.

So, let’s consider a pool of water. The pool is described by two conjugate variables: the volume of water, and the height of the water.
[Read more…]

The black hole: Zoom in, enhance!

A few days ago, scientists announced the very first real image of a black hole (as opposed to one of those “artist’s conception” images that you see everywhere).

blurry ring of light

Black hole Messier 87 (aka M87) (credit)

This was a very nice surprise, because I was not aware any such project was underway, and I would have thought the obstacles were too great.  The main problem with imaging black holes is that black holes are really far away.  You would have to “zoom in and enhance” many many times to get the image above.  Let’s compare it to other examples of extreme zooming.

[Read more…]

Origami: Truncated octahedron

truncated octahedron

Truncated Octahedron, designed by me.  I kept this on my office desk.

Today’s model is one of my earliest original designs.   This is a truncated octahedron, which is the shape you get when you take an octahedron, and chop off the 6 tips.

I was interested in designing a model with this particular shape, because it has some special significance in condensed matter physics.  There’s a certain kind of crystal structure, called the “body-centered cubic structure”, which looks like this:

[Read more…]