Of Water Worlds and Desert Planets

Everyone learns in primary school that the surface of the Earth is about 70% ocean and 30% dry land. But is there any reason to believe that this is the norm across the Galaxy? In this paper, Fergus Simpson argues that most habitable planets should actually be "water worlds," i.e., planets covered entirely with water.

Dark Matter - Where is it ???

Last month I discussed the experiments using vast tubs of liquid xenon to search for dark matter. It turns out to have been a prescient post, because yesterday the scientists from LUX (a liquid xenon experiment buried deep under the Black Hills in South Dakota) posted their latest results. And they saw.... absolutely nothing.  LUX is the most sensitive experiment of its kind, and these scientists were able to push down upper limits on how strongly the dark matter interacts with ordinary matter by a factor of 4.

So why haven't we detected dark matter yet? It might still be hiding just below the current sensitivity of our experiments. But it's also possible that we're barking up the wrong tree.

Popular Culture Down the Memory Hole

Popular culture is by its very nature ephemeral. Today's famous actor or musical hit is tomorrow's trivia question. But some types of pop culture are more ephemeral than others, and there's one area that's vanished so thoroughly that it's left almost no trace at all.

See if you can fill in the blanks:

I'd rather fight than _____
I'd walk a mile for a _____
A silly millimeter _____
You've come a long way, _____

My guess is that everyone over the age of 50 will recognize the answers instantly, and nobody under the age of 40 will have the slightest clue what I'm talking about. So what are the answers?

Mars, and its Rival

For those of you in the Northern Hemisphere, there's a spectacular sight near the southern horizon in the early evening. ("Spectacular" here is a relative term when applied to the night sky -- I'm not talking Disney-fireworks-over-Cinderella's-Castle spectacular). If you look to the south, you'll see a very bright, reddish-looking object -- that's Mars. And if you look to the left of Mars, you'll see two other bright objects. The lower one also has a reddish hue. It's Antares, a red supergiant and the brightest star in the constellation Scorpio, the scorpion. (Yes, I know that none of the constellations looks anything at all like its assigned name. Aside from the Big Dipper). Antares actually means "rival of Mars," because of its red coloration, so this is a rare chance to compare Mars and its rival right next to each other. I'm afraid I'll have to go with Mars -- Antares is pretty weak competition.

Metrology -- the Boring Science

As promised, here is the short SF story I wrote on the topic of metrology, the study of "weights and measures."  It's "Equivalence Principle" and it appeared in the Jan/Feb 2004 issue of Analog. The story itself was inspired by a lecture I attended on string theory -- the speaker emphasized that physics was all about unifying disparate physical quantities, such as time and space, and mass and energy. It just shows that you can write a story about any topic, no matter how seemingly boring...

The Elements Nobody Talks About: Iridium

Do you know anything about iridium? Perhaps you've heard of the Iridium satellites, which were launched to serve as the basis for a satellite phone system. They're so reflective that they occasionally produce "Iridium flares," -- bursts of light that briefly outshine everything in the night sky except the Moon. If you've never seen an Iridium flare, then you should -- they're pretty impressive. The flares are extremely localized, so you need to go to the website Heavens Above, enter your location on the map (scroll all of the way in until you can see your own house!) and then click on the Iridium flare tab on the left. You'll get a list of flares that you can see from your location, including both the exact time they start, and where to look in the sky. Don't waste your time with any of the weak flares -- wait for one that's magnitude -5 or brighter. (In their typical contrary fashion, astronomers denote brighter objects with lower magnitudes -- blame the ancient Greeks).  Be sure to have an accurate time-keeping device -- the flares only last for a few seconds.

What do the Iridium satellites have to do with the element iridium? As far as I can tell, absolutely nothing -- the name just sounded impressive. (Which leads to an interesting question: can you trademark the name of an element?)

So what is the story with iridium? It's one of three sister elements with similar chemical properties; osmium, iridium, and platinum. Platinum is the Cinderella princess of the three -- a "precious metal" used in jewelry -- while osmium and iridium are the ugly step-sisters. But iridium plays a central role in science....

Help -- One of our Stars is Missing!

Suppose there were amazingly advanced alien civilizations out there -- aliens capable of harnessing the energy of entire galaxies. (These are the Kardashev Type III civilizations). Surely such a civilization would easy to spot?

I've noticed a surprisingly large number of serious astronomy papers on this subject recently. As you might imagine, nobody has seen any evidence for such a civilization -- if they had seen something, you probably would have heard about it by now. But here's a fun new idea from Beatriz Villarroel and collaborators at Uppsala University: searching for disappearing stars. These scientists compared two surveys of the sky -- one from the US Naval Observatory, based on observations of the sky between 1950 and 1999, and the more recent Sloan Digital Sky Survey. They examined 10 million objects, and found exactly one object in the first survey that seems to have disappeared in the later survey.

Does this mean that an advanced civilization has caused a star to vanish?

Are There Aliens in our Future?

Avi Loeb, who's one of the most creative people in my field, posted a paper yesterday exploring the likelihood of life in the universe as a function of time. He and his two collaborators argue that life is far more likely to arise in the distant future of the universe than it is today. Why?

The Elements Nobody Talks About: Xenon

The inert gasses (helium, neon, argon, krypton, xenon, radon) are the elements you never hear much about. Sure, we worry about radon gas, and helium gets a good workout in balloons, but when was the last time somebody mentioned krypton at a cocktail party? (Come to think of it, when was the last time you actually attended a cocktail party?) The inert gasses are the lazy elements -- they just lie around all day in the hammock and never do anything. If I were an element, I would want to be be an inert gas.

And that applies especially to xenon. Until recently, if you'd asked me about the main uses of xenon, I would have said it was useful primarily in Scrabble. But within the last couple of years, xenon has become one of the most important elements in cosmology.

Robert Heinlein and Intellectual Fads

I just finished the first volume of William Patterson's massive two-volume biography, Robert A. Heinlein: In Dialogue with his Century. It suffers a bit from the curse of too much information; e.g., "Shortly after selling his second story to Astounding, Heinlein feasted on a breakfast of bacon and scrambled eggs. The bacon was crispy, but the eggs were too runny. There was no toast." OK, I just made that up, but you get the picture. I'm being a bit unfair, as the most interesting thing about this book is the detailed picture it paints of pre-WW2 American society, especially Heinlein's life at the Naval Academy and his early career in the U.S. Navy. Like many science fiction readers, I had always thought of Heinlein as a writer with a brief and unimportant stint in the Navy. But Heinlein had planned on a life-long naval career before being forced to retire for health reasons -- I am sure that in a parallel universe somewhere he led the Pacific Fleet to victory against the Japanese.

Patterson also highlights another striking aspect of Heinlein's life -- his tendency to fall for many of the more unusual intellectual fads of his day. While he often presented himself as a hard-bitten empiricist, Heinlein latched onto some of the most bizarre variations of socialism in the 1930s, and he was a big fan of general semantics. What's that? You've never heard of general semantics? But it was all the rage -- or at least it was 80 years ago. Promulgated by "Count" Korzybski, it promoted "non-Aristotelian logic." As far as I can see, its major contribution to Western thought was its use as a basis for A.E. van Vogt's novel, The World of Null-A.

New Element Named After Tennessee

I couldn't let the day pass without noting that the International Union of Pure and Applied Chemistry, which certifies the names of newly-discovered elements, has recommended that element 117 bear the name of "tennessine,"  in honor of the joint discovery of this element through work at Oak Ridge National Laboratory, the University of Tennessee, and the efforts of two of my colleagues here at Vanderbilt.

Graduation Season

I journeyed up to the "Garden State" for my oldest son's college graduation this past week. (I've always assumed that New Jersey's nickname was some sort of obscure joke):

The Garden State. Really???

In the course of sending my children through college I have come to this deep revelation, which I will now share with you:

Mothers cry when their children go off to college.
Fathers cry when they can no longer claim their children on their income taxes.

Playground Physics

Playgrounds are a great place to learn some basic physics. Or at least they were 50 years ago, before the safety mavens moved in and rebuilt everything in plastic and foam rubber. Take a look at this old seesaw:

The physics lesson is right in the center: the seesaw rested on an open pivot, so that you could just lift it up and move it, making one side shorter than the other. This was a perfect illustration of a lever -- a lighter kid on the longer end could easily balance against a heavier kid on the shorter end. At least until one of them jumped off, sending the other crashing to the ground. But it was the movable pivot that doomed this particular type of seesaw. You can see how easy it would be to get your fingers crushed in the center. I never actually saw this happen, but we all lived in dread of the possibility.

An even more interesting physics demonstration was the old-fashioned merry-go-round:

The game here was to push the merry-go-round as fast as possible, until centrifugal force almost flung everyone off. Disclaimer: we teach all of our college freshmen that there's really no such thing as centrifugal force. The force actually points inward, and it's called "centripetal force." But if our students go on to a more advanced class, they learn that there really is such a thing as centrifugal force, but it's a "fictitious force" --  a force that only appears in an accelerating frame of reference. So when you're flung off the merry-go-round and scrape your legs while sliding across the concrete, you can comfort yourself with the fact that it was only a fictitious force that threw you across the playground.

Galaxy Quest

I watched Galaxy Quest again the other night. It's a hilarious spoof of Star Trek -- a group of washed-up actors from a cancelled science fiction TV series are mistaken for the real thing by aliens who have intercepted their TV broadcasts and who need their help to defeat their ruthless foes.

Chipmunk Delenda Est

I am engaged in an ongoing war with a family of chipmunks that has taken up residence in a narrow strip of ground between my house and our outdoor fish pond. They are perilously close to burrowing through the pond liner, unleashing a thousand gallons of water against the base of my house.

While the chipmunks and I are evenly matched intellectually, I am thus far in the lead, 2-0. But my battle against the chipmunks led me to this scenario:

Imagine that the doorbell rings, and you go to the front door to discover an unexpected package from Amazon. The box is strangely wrapped, and some of the words are misspelled, but you can see that it's stuffed full of money -- some of the cash is leaking out of rips in the cardboard. So you lean over to pick up the box and... thwack! Revenge of the chipmunks.