Friday, July 29, 2016

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.

Friday, July 22, 2016

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.

Wednesday, July 20, 2016

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?

Thursday, July 14, 2016

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.

Wednesday, July 13, 2016

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...

Monday, July 11, 2016

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....

Wednesday, July 6, 2016

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?