Tuesday, July 11, 2017

The Physics Problem that Isaac Newton Couldn't Solve

I spent the year before graduate school doing research at the Institute of Astronomy in Cambridge. While I was there, Martin Rees (later Sir Martin, and now Lord Rees) gave a talk to the new graduate students on the best way to choose a Ph.D. dissertation topic. I remember him saying, "Don't choose a problem that Poincare couldn't solve. Choose a problem that Poincare never heard of."

But let me dial up the challenge even more. There's a physics problem so difficult, so intractable, that even Isaac Newton, undoubtedly the greatest physicist who ever lived, couldn't solve it. And it's defied everyone else's attempts ever since then.

Monday, June 26, 2017

Star Trek Dentistry

Upon reaching a Certain Age, your teeth begin to disintegrate -- something to look forward to, kids! Thus it was that I found myself sitting my dentist's office last week, waiting for a new tooth. What I hadn't realized is that dentistry has, over the past decade, entered the era of Star Trek.

Thursday, June 22, 2017

If You Miss Next Month's Eclipse...

In just one more month, the city of Nashville will host part of the Great American Eclipse. I can already feel the excitement building, along with the email inquiries about housing in the area. If you're planning to drive somewhere to view the eclipse, book your hotel early and drive to your viewing destination well in advance. The traffic leading up to the eclipse is going to look like a hurricane evacuation in reverse.

But what if you miss the eclipse? Suppose it's overcast that day, or your car breaks down on the way? No need to despair -- there's another eclipse across the middle of the US only seven years later, in April of 2024.

Thursday, June 15, 2017

The Next AI Frontier: Teaching Computers to Lie

I got into a minor kerfuffle over at Steve Hsu's blog when I commented on this post about AlphaGo, the neural net program that has blown away all of the human competition in the game of Go. I said that I would be more impressed when computers mastered Diplomacy, a comment which was immediately challenged by someone else. But as impressed as I am with AlphaGo, I stand by that comment.

When I was a kid back in the 60s, the local science museum had a computer that played tic-tac-toe. (The local fair had a pigeon that played tic-tac-toe, but maybe that's a topic for another day). I have no idea how the computer worked -- maybe an analog circuit of some sort? The London science museum at one point had a tic-tac-toe computer constructed from Tinkertoys and string. As primitive as these sound, I think you can draw a straight (but very steep!) line from tic-tac-toe to the computer that "solved" checkers, and then to IBM's Deep Blue (which conquered chess), and finally to AlphaGo. These games (tic-tac-toe, checkers, chess, Go) are all deterministic with perfect information, in which the players alternate taking turns, choosing from a finite number of moves. (To be fair, there is a qualitative leap between the earlier "brute force" programs, which relied on simply increasing the number of moves scanned by the computer, and AlphaGo, in which the computer actually "learns" to play better, and in which it's impossible for the programmers to determine why the computer chose a particular move.)

Diplomacy is a very different animal. For those of you not familiar with the game, it's a contest of almost pure negotiation, requiring the ability to form alliances, offer bribes, bluff, lie, and backstab your way to the top. It requires a very different, more "human" set of skills than chess or Go. Computer scientists are already working in that direction, particularly with the game of poker.

I myself wrote two chess programs back in the 1970s, one in high school (in BASIC), and the second in college (in Fortran, the One True Programming Language). Both of my programs were, in one sense, more advanced than Deep Blue. They cheated.

Friday, June 9, 2017

Fr. Georges Lemaitre and Cosmology

If you'd like to see my talk on Fr. Georges Lemaitre and his contributions to cosmology, there is a video posted here. You'll find me about half-way down on the right-hand side. The other talks were also very interesting and definitely worth your attention.

Thursday, June 1, 2017

The Smartest Person Who Ever Lived

Who was the greatest genius in human history? Einstein? Newton? Mark Zuckerberg? (Hint: not Mark Zuckerberg). My vote goes to someone who probably died about 3000 years ago on the shores of the Eastern Mediterranean.

Tuesday, May 30, 2017

The Mystery of Cosmic Lithium

When most people think of lithium, they probably think of antidepressants, or possibly lithium batteries. But to a cosmologist, lithium is the misshapen puzzle piece -- the one that won't quite fit, no matter how hard you push it.

What does lithium mean to you?
Most of the elements were produced in the nuclear furnaces of stars or supernovae, but a handful were made in the first few minutes of the universe, when it was incredibly hot (billions of degrees) and dense. These big bang elements include helium, deuterium (a form of hydrogen with an extra neutron) and one isotope of lithium. Our theory, called "big bang nucleosynthesis," gives beautiful agreement with the observed helium and deuterium abundances, but it fails miserably for lithium -- the theory predicts about three times as much lithium from the big bang as we actually observe.

So what's going on here? As one of my high-school teachers used to say, "half-right equals all wrong." But the fact that big bang nucleosynthesis works so well for helium and deuterium suggests that maybe it just needs a few tweaks, instead of wholesale reworking. Roughly speaking, there are three likely alternatives:

Thursday, May 25, 2017

Physics in the Year 2116

Last year Physics Today ran an essay competition called "Physics in 2116." The idea was to write a science article that might appear in Physics Today 100 years from now. Motivated largely by the enormous prize money, I entered the competition but, alas, mine was not among the winning entries. As the article itself is not really suitable as either a science fiction story or a nonfiction article, I am presenting it here for your amusement. Be sure to read the footnotes.

Friday, May 19, 2017

Lies, Damned Lies, and Astronomy Photos

I'm sure you've all see beautiful images like this NASA photo of the Crab Nebula:

Who you gonna believe, me, or your own eyes?

Just imagine if you looked at the Crab Nebula through a powerful telescope -- you'd see something that looked... nothing at all like this. That's because the colors in astronomy photos are almost never the "true" colors that you would see with the naked eye. They're "false color" photographs, with different colors assigned to different wavelengths of light or (in this case) to images derived from different telescopes.

When I first realized that false color photos were the standard in astronomy, I was dismayed. What else had NASA been fibbing about? The Moon landings? But NASA hasn't been lying at all, and there's no reason to get upset about false color photos. And here's the reason why: your own eyes give you a false-color picture of reality.

Monday, May 15, 2017

Germany's Famous Science Museum

I spent last week in Munich -- my first visit to Germany in 30 years. At this point, I am supposed to insert the obligatory paragraph expressing shock and surprise at how much everything had changed. But frankly, Germany didn't seem all that different from the last time I was there. Societies have a lot more cultural inertia than we realize.

My personal high point of the trip was a visit to the famous Deutsches Museum, the top German museum of science and technology.  It's the largest science museum in the world, and a true monument to Teutonic thoroughness: why include just a few slide rules in your computing exhibit, when you can display one of every type of slide rule ever made?

The high level of the exhibits is remarkable, especially compared to U.S. science museums, which have largely been dumbed down to the level of children's museums in the course of my lifetime. The Deutsches Museum tilts heavily toward physics and engineering -- we skipped the exhibits on machine tools and metallurgy.  But I learned quite a few fun things in the course of my visit:

  • Despite the fact that the wheel was known in ancient times, the wheelbarrow was not invented in the West until the Middle Ages.
  • It's possible to slice a torus (i.e,. a donut) along a Mobius-strip-shaped cut, so that the torus gets cut all of the way through but doesn't fall into two pieces (that's really hard to explain in words, but the museum had a nice model to demonstrate).
  • Germans apparently have a much longer attention span than Americans -- all of the push buttons on the exhibits required you to hold them down much longer than would be the case for an American museum. Several times I thought an exhibit was broken, only to discover that I had not depressed the button long enough.

Thursday, April 27, 2017

First Conference of the Society of Catholic Scientists

The new Society of Catholic Scientists held its inaugural conference last weekend in Chicago -- you can read all about it at the Forbes website here. I thought the conference was enormously fun. It's a sad fact that most of us in academic science end up funneled into narrower and narrower specializations, until we end up talking almost entirely to other people in our own field. In Chicago I got to meet a Penn paleontologist who digs up dinosaur fossils in Western China, an MIT linguist studying the birth of human speech (who also loves science fiction!), and a Harvard astrochemist examining the possibilities for life on other planets.

My own talk was on Georges Lemaitre, the Catholic priest who pulled together various observational and theoretical threads in the 1920s to develop the the Big Bang model. Modern cosmology had many fathers, but only one Father.

Wednesday, March 29, 2017

A New Email Low

I've hit a new low -- Vanderbilt's spam filter blocked a message I sent to myself. It says that I might not be the person I claim to be. I guess that's true.

Tuesday, March 28, 2017

Galileo and Dark Matter

I was drafted recently to give a talk about Galileo, a subject on which I am no expert. So I relied heavily on Rocky Kolb's book, Blind Watchers of the Sky (I wrote my very first physics paper with Rocky back in 1981, back when we were both, uh, about 12 years old), and on Michael Flynn's brilliant, if somewhat irreverent (coming from me, the latter is higher praise than the former), The Great Ptolemaic Smackdown.

When doing scientific research, you quickly come to realize that progress in science consists of thousands of blind alleys (for you), punctuated by the occasional breakthrough (for someone else). In the textbooks, all of the blind alleys get airbrushed away (who has time to study incorrect theories?), leading to the erroneous impression that science has been been one long march to the Truth. But it never happens that way.

For example, one of Galileo's main arguments for the Copernican model was his theory of the tides. He noticed that as the Earth moves around the Sun, the surface is moving faster at midnight than at noon, since in the former case the motion around the sun is in the same direction as the rotation of the Earth, and vice-versa at midnight.




So Galileo claimed that the water would bunch up at noon and spread out at midnight, leading to a low tide at midnight and high tide at noon (or maybe the other way around?)  A couple of problems here:  there are two high tides and two low tides a day, not one, and they occur at different times of the day, not just noon and midnight.  Galileo's theory was completely wrong, which is why you've never heard of it (except for you, Michael...)  But (and this is the weird part), I drew a diagram exactly like this one for my cosmology class a few weeks ago. Why?

Tuesday, March 14, 2017

Science Fiction Set In Your Home Town

If you grew up in New York or Los Angeles, you'll find no dearth of science fiction set in your home town, with familiar locales and landmarks. The same thing applies if you were born in Trantor, Diaspar, or Coruscant. But if, like me, you come from the Midwest, you won't see a lot of local color in the science fiction you read.

I grew up in St. Louis, so I was delighted to encounter The Jericho Iteration, by Allen Steele. Steele's novel is a science fiction conspiracy thriller set in a St. Louis devastated by an earthquake on the New Madrid fault. I enjoyed recognizing the numerous local landmarks in the novel, although I didn't actually like the story itself. But that's beside the point -- the important thing is that St. Louis has a science fiction novel to call its own.

I should also mention that the near-future dystopian film Escape from New York was filmed in St. Louis, despite being set in New York. Apparently New York was insufficiently run down to serve the filmmakers, so they came to St. Louis instead. Now that's something for a native St. Louisan like me to be proud of.

What about my adopted home of Nashville?

Wednesday, March 8, 2017

Texas Talk on Science and Science Fiction

I'm giving the physics colloquium at Texas A&M tomorrow (Thursday, Mar. 9) on science and science fiction. Details are here.