## Thursday, November 26, 2015

### Woodrow Wilson Trivia Question

Some of you might have noticed the recent kerfuffle about the position of Woodrow Wilson at my alma mater, where it seems like every other building is named after him. The reason for all of this Wilson hagiography is that Wilson was not merely a graduate of Princeton who became president of the United States, but that he was also a faculty member at Princeton and, ultimately, president of the university itself.

As I was contemplating the fact that Wilson was the only university president ever to become president of the United States, I realized that his career path was not unique. There is one other man who served as a university president before being elected president of the U.S. Can you name him? (Hint: like Wilson, he was the head of an Ivy League university).

## Tuesday, November 24, 2015

### Could We Still Exist if the Constants of Nature Were Different?

Physics is characterized by a handful of "fundamental constants."  For instance, the gravitational constant, G, tells us the force of gravity between different masses.  Similarly, the "fine structure constant" gives the electric force between two charges.  Does our existence depend on the values of these constants?  If they were different, could life still exist?

## Tuesday, November 17, 2015

### Probability and Statistics in Science Fiction

My previous post on mathematics in science fiction had a serious omission -- I ignored probability and statistics. These two subjects are often lumped together, but they are, in a way, opposites. In probability, you know the rules of the game ahead of time (I roll a die, and each number from one to six is equally likely) and you have to calculate the odds of various outcomes (how likely is it that I will roll three sixes in a row?)  Statistics is just the opposite:  you are given the outcomes and are trying to figure out the rules of the game. If you have a bunch of "data", what is the likelihood that they were produced from a particular model of the universe? In his book Numerical Recipes, Bill Press and his collaborators describe statistics as "that gray area which is surely not a branch of mathematics as it is neither a branch of science."  I couldn't agree more.

Probability is clean and precise, and I really enjoy it.  I've written several papers about the pattern of galaxy clustering in the universe (technically, this is called the "large-scale structure" of the universe) based largely on different aspects of probability theory.  Probability is my friend.

Statistics, on the other hand, is not my friend.  It's a necessary evil, like a decennial colonoscopy. Statistics is the Norse trickster god Loki -- it's slippery and untrustworthy.  There are even different sects within statistics whose members base their analyses on completely different fundamental assumptions.  For example, you can be a Bayesian or a frequentist -- these two groups fought an inconclusive war that devastated Germany in the 17th century.  (By the way, don't believe everything you read on the internet). For a less jaundiced and undoubtedly more accurate view of statistics, read the various posts on Michael Flynn's blog, such as this one.

## Tuesday, November 10, 2015

### Our Linguistic Debt to Chickens

There are four chickens living in my back yard. How did they get there? What road did they cross to get to my yellow slide? It happened in much the same way that I ended up with a dog: I returned home from work one day and discovered that we had adopted a small flock of chickens. So I am now the proud owner of a Metro Public Health Department Domesticated Hen Permit.

Once, after asking my kids if the chickens were "cooped up" for the night, and thinking about the "pecking order" that the chickens had established, I realized how many everyday English words and expressions we owe to chickens, and how accurately they describe the actual behavior of chickens.

## Monday, November 9, 2015

### No Radio Signals from KIC 8462852

Well that didn't take long. The SETI folks used the Allen Telescope Array to look for radio emissions from the star KIC 8462852 -- that's the star I discussed last week that shows an unusual pattern of dimming and brightening. You can read the scientific paper here. (They've got to find a shorter name for that star. How about KIC MEE?). So what did the SETI investigators hear over the radio?

## Friday, November 6, 2015

### Sailin' Through the Solar System

I first encountered the idea of solar sails in the Arthur C. Clarke story, "Sunjammer."  Yesterday, Les Johnson came up from the Marshall Space Flight Center in Huntsville to give an excellent talk on this topic -- I learned a few fun things I hadn't known before.  But first, a trivia question:  Do solar sails operate by catching the solar wind?

## Wednesday, November 4, 2015

### Mathematics in Science Fiction

Are there any examples of science fiction in which math plays the central role?  Before examining that question, let me pose a simpler one: is mathematics a branch of the sciences, like physics or astronomy?

## Monday, November 2, 2015

### Have We Discovered a Dyson Sphere Under Construction?

Many of you have probably seen this article over at The Atlantic.  The basic story is that the Kepler mission, which is designed to look for planets orbiting other stars, has turned up something very strange.  And no one is exactly sure what it is.