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:

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.

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.

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.