Monday, November 27, 2006

A match made in heaven

I read a couple of interesting articles on the web last week, but didn’t see how they relate to each other until just now.

The first was an article by the New York Times, describing how Mythbusters is the best science show on television. I happen to agree with this sentiment. If fact, I know of no other TV show that demonstrates how to test and refine a hypothesis as well.

The second article was a blog at Arms Control Wonk about how a nuclear weapon could be built from surplus military equipment (and a whole pile of Uranium). What really caught my notice here was the number of people who commented on whether the method described would work, and how it could be improved.

Now, I don’t entirely understand the temptation to post recipes for nuclear weapons on the internet- I’ve personally never uploaded instructions for creating anything more dangerous than a chocolate chip cookie. But my scientifically trained eye did notice that this wide variety of opinions and unsubstantiated prognostication did indicate a glaring shortfall: The lack of experimental data. And that’s where Mythbusters comes in.

Adam and Jamie are the masters of refuting bombastic urban legends through experimentation. So instead of polluting the internet with untested ideas, perhaps we should just give the Mythbusters the following hypothesis:

Myth: Shooting two bits of highly enriched uranium together will cause a nuclear explosion

It would be a win-win episode. If the myth us busted, then we could all breathe easier at night, knowing that nuclear terrorism is more difficult than it appears.

If the myth is partially confirmed- say, by a North Korean-style fizzle that irradiates all of Petaluma, then we can emphasize the unpredictability and danger of playing with critical masses of fissile material.

And finally, if the myth is confirmed by vaporizing the entire San Francisco metropolitan area, then at least we have the sort of visual spectacle that is appropriate for a season finale. Such a prospect might even appeal to the ultra-conservative Republican base, a community that could use a bit of extra scientific education.

If it's a hit, we could even follow it up with a test of some similar myths. For example:
Myth: Anthrax can be passed through the mail.
Myth: Most of today's population has lost resistance to small pox.
and finally
Myth: A large scale nuclear war will offset global warming with nuclear winter.

Sunday, November 26, 2006


Last week, the former Russian spymaster Alexander Litvinenko was killed by radiation poisoning after ingesting a dose of 210Po. I am not qualified to comment on the political ramifications of this radiological attack, I can give the bare-bones information on 210Po.

There are three basic ways to make short-lived radionuclides here on Earth. The first is to collect the short-lived intermediate decay products of Th or U isotopes, which undergo complex decay chains from the relatively stable initial isotopes, through increasingly unstable decay products, to Pb, which is stable. The second is to fission a heavy nuclide into unstable daughter products. The third is to irradiate a stable or long-lived nuclide such as 39K, 238U or 59Co in a reactor or particle accelerator to produce a less stable daughter, like 39Ar, 239Pu, or 60Co.

210Po -> 206Pb is the final decay in the 238U -> 206Pb decay system. As such, it is present in natural uranium ore in concentrations that are inversely proportional to the ratio of the decay constants of 210Po and 238U . This ratio is about 8.6x10-11. So for every kg of U in natural ore, there is 86ng of 210Po. (alternatively, that is 86ug/ton).

There have been reports that the soviets stockpiled 210Po during the cold war. While this may be true, it is unlikely that this is the source for the poison used today. 210Po has a half life of 138 days, and the cold war ended about 5800 days, or 14 210Po half-lives, ago. Thus essentially all of a cold war stockpile would have disappeared by now.

There are several options for 210Po generators, including 210Pb (half-life 22 years), and 226Ra (half-life 1600 years). In fact, polonium was originally discovered by Marie & Pierre Curie, after their isolation of Radium.

210Po can also be formed by neutron irradiation of 209Bi, at least according to Wikipedia. It is not abundant in spent nuclear fuel.

Anyway, the point of all this is that whoever killed the guy must have had access to either a reactor, a supply of the highly radioactive isotopes 226Ra or 210Pb, or an industrial scale U processing facility and a chemistry lab that can deal with serious amounts of radiation. It is way more sophisticated than stealing a spent fuel rod or a medical radiation source, and thus is considerably more worrisome than a mere dirty bomb. This radiological attack was obviously perpetrated by someone who knew what they were doing, and had access to some serious infrastructure.

Friday, November 24, 2006

Happy Thankgiving

I hope yours is as joyful, stress-free, and turkilicious as ours was.

From start.

To finish.

Saturday, November 18, 2006

Phase equilibria of pie crust

With American Thanksgiving and Christmas rapidly approaching, the pie baking season is rapidly approaching. One of the most important, but least quantified, aspects of pie creation is the crustal composition. A simple ternary phase diagram for three-phase pie crust is presented below.

While the “traditional composition” point is plotted to scale, the positions and shapes of the curve are poorly constrained approximations. Lack of accurate thermodynamic data for the system precludes accurate prediction of these fields. It is the shapes and positions of the top two curves that is of paramount importance; anyone who reaches the butter-water two phase field should be banished from the kitchen.

As anyone with baking experience knows, the stability region for pie crust is a relatively small area on the wet side of the two phase flour + dough field. This field is generally approached by adding water to a flour/butter mixture, as is shown below.

However, if the approximated slopes shown above are correct, then a radical new approach to crustal formation might be advisable. By generating a flour-water mixture, and then adding butter, a wider range of valid crustal compositions should be achievable before exiting the edible portion of this phase diagram. This approach is shown below.

I will be baking at least three pies this week for T-day. I might have a go at this radical new approach, to see if it yields additional information on the slope of the upper two phase boundaries. I suspect they might be steeper than the lines shown here. Assuming I can actually get a cheap, accurate kitchen scale, there may be more reports on the thermopienamics of this system sometime next week.

Thursday, November 16, 2006

Wednesday, November 15, 2006

Eye of Newt and blur of science

Double double toil and trouble.
Fire burn and cauldron bubble.

One of the problems facing scientists and science promoters is that the human brain has not evolved to naturally gravitate towards clever experiments or robust theorems. As a result, journalists and educators often resort to using a variety of non-scientific techniques to catch the public’s interest or to explain the significance of a particular discovery. The problem with this approach is that it blurs the borders between science and the non-scientific tools used for education. It is difficult to complain about liturgists, fraudsters, or entertainers intruding into the arena of science when their traditional techniques are used for science promotion.

I suspect that entire journals could be filled with theories, explanations, or apologies for various aspects of and solutions to this problem, but being an illiterate lab techo, I haven’t read any of them. So I will ignorantly suggest a simple way of judging the usefulness of any particular unscientific selling technique: the cost-benefit analysis. If a particular method has limited explanatory power, and has a high chance of causing confusion or misunderstanding, then it should be avoided. One such high cost, low benefit literary device is nomenclatural overload, and its poor cousin, technobabble.

Modern science is complicated. But despite that complication, the particular experiments and observations that are undertaken are generally done for specific, definable reasons. Simply dumping the names or generalizations about a field onto the page without explaining them merely creates the illusion that science is a collection of arcane trivia, and not the amalgamation of knowledge based on prediction and observation. The practice of name dropping and information overloading has the effect of reducing science to alchemy, where arcane ingredients are combined and channeled without any overarching principles. This is obviously a risky approach:

Adder’s fork, and blind worm’s sting,
Lizard’s leg, and howlet’s wing-
For a charm of pow’rful trouble,
Like a hell-broth boil and bubble.

The solution is fairly obvious- if you’re writing an article, explain why things are important before you discuss what the result of measuring them was. An example of how this should, but doesn’t happen can be found in this week’s New York Times science section, in the article, "Ancient Crash, Epic Wave."

The offending excerpt:
“When a chondritic meteor, the most common kind, vaporizes upon impact in the ocean, those three metals [iron, nickel and chrome] are formed in the same relative proportions as seen in the microfossils, Dr. Abbott said.”

The reason behind these analyses is fairly simple, so it is a shame that this otherwise excellent article didn’t bother explaining it. For any non-geologists who have wandered into this site by accident, here is the story:

When the planets and asteroids originally formed early in the solar system’s history, the larger ones heated up and melted, and the immiscible liquid metal and molten rock differentiated to form a metallic core and a silicate mantle. Small asteroids did not generate enough heat to melt, and remained undifferentiated. These are the chondrites, and they contain a mix of metal and silicate that condensed from the primordial solar nebula.

Because the Earth is differentiated, most of the elements that dissolve into metal instead of magma are contained in the core, and thus are relatively rare at the surface. These elements, called “siderophiles” (iron lovers) are thus more common in undifferentiated bodies than they are in the Earth’s crust. So when a chondrite hits the earth, the ejecta is enriched in siderophiles such as Fe, Cr, and Ni. Iridium is also a siderophile, so the search for nickel and chromium is based on the same principle as the search for the Ir anomaly at the K/T boundary, which marked the end of the Mesozoic (the age of dinosaurs).

Obviously, these elements are not “formed” in the impact. They are just particles from the impactor, which can be identified because the impactor and the silicate Earth have very different siderophile concentrations.

Of course, getting scared off by terminology and avoiding it is just as problematic as simply namedropping undefined terms. But in science, things often have names for a reason, so explaining what that reason is can go a long way towards illuminating the subject at hand.

Saturday, November 11, 2006

A bit of perspective, lab style

High School science is not a particularly memorable period in one’s journey through life. The science geeks generally know everything already, while the people who don’t really care are hardly inspired to learn. But my second year of high school physics had a few memorable labs.

Our school didn’t have the funds/ organization/ inclination to offer AP physics, so the “advanced” physics had one of the physics teachers dredging up all this crazy ancient equipment and teaching us the physics that they demonstrated. There were two labs, in particular, which I remember.

The first was digging up and fixing an old single grating diffractometer and looking at the discharges from various gas tubes to learn all about both diffraction and gas excitation. The culmination of this was figuring out what the fluoro tubes that lit the lab must be filled with- it was easy to look up, but cool to see that ordinary real life was made of the same elements, wavelengths, and concepts that were stored in the back of the physics cabinet.

The second lab I remember was radioactivity. The cabinet (perhaps set up by Dr. Calgari?) contained a half a dozen Geiger counters. First we learned safety procedures- which include Geiger-countering each other at the end of each lab to detect spills. Next, we looked at the radioactivity of various normal or natural items. Finally, the teacher brought out the radioactive generators. These were little disk-shaped things, about the size of a small stack of poker chips, through which a dilute acid was poured. The liquid that emerged was radioactive, and our task was to count it throughout the class to determine the halflife, from which we were to identify the isotope being extracted. I know I got the isotope wrong, and I still can’t remember what it was, exactly- the halflife was less than the class length, though, so my best guess- 15 years later- would be 223Fr.

Of course, we all had to Geiger-counter each other at the end, just to make sure nobody spilled anything, and this is where some clown snuck the pitchblende ore up behind the counter as it dropped past the beltline of a particularly nervous doctor wannabe. Being a fairly excitable sort of kid, he went on for weeks about how dangerous and stupid the entire lab was, how those extra handful of decays had needlessly put him at risk, and all the other prattlings of an angry, humiliated young man.

He sort of had a point- I mean, radiation is dangerous, and even though we were generally well-behaved and conscientious, I’m not really sure what would have happened if somebody had spilled a beaker on themselves. But the magnitude and importance of the risk was brought into clearer focus after Christmas that year.

When we came back from Christmas break, our physics teacher was gone, and the school’s other teacher took over the class for the rest of the year. We graduated in 1991, and our teacher, who was in the army reserve, had been called up to teach kids a year older than us how to drive tanks, in preparation for the liberation of Kuwait in the first gulf war.

No longer was he teaching us the physical processes illustrated by trace concentrations of U decay chain products. Instead, he was showing army recruits how to take care of, load, and fire shells made of depleted uranium.

It was then that we realized that all of the chemistry, physics, and other science that we were taught to use caution around was also used for the deliberate killing of other human beings. It is one thing to have a bottle of nitrates say, “warning: fire hazard.” It is another for someone to use the same basic decomposition reaction in a bomb or shell aimed at your head. Technology can do some nasty things to the human body, and one of my key high school revelations was that people my age would willingly put themselves in the way of technology’s most dangerous creations.

Needless to say, complaining about a high school lab seemed a little bit petty compared to the idea of going off to war. This realization was heightened when I turned in my selective service card at the post office on the President’s deadline for Iraqi troops to leave Kuwait. The bombing campaign started 2 days later.

Today is Remembrance Day. So spare a thought for all the service men and women who are putting themselves in harm’s way. They put themselves in the way of science’s most destructive and lethal applications, so that we don’t have to worry about anything more traumatic than traffic, or eye strain, or any of the other molehills that we tectonically uplift in the day to day existence of our overly civilized lives.

Wednesday, November 08, 2006

Jan Veizen’s cosmic ray climatology

Last week we had Jan Veizen, a long-ago ANU alumnus, come back to give a talk about how hew thinks that Phanerozoic climate is primarily governed by cosmic rays. I am not a climatologist, so I can’t really get into the nitty-gritty details. Additionally, it was a fairly qualitative presentation, so this reflection is similarly mushy. There was a fast one that he tried to pull, and there was an abundance of sketchy science that is worth repeating.

First of all, Professor Veizen did repeatedly state that he was not in favor of polluting, and that he thought it was a generally bad idea. But he also concluded that CO2 climate sensitivity was overestimated because it did not create a water vapor feedback. The trouble is, even if we accept his overall model, the application of it to anthropogenic climate change is not necessarily appropriate.

Professor Veizen’s thesis basically goes like this:
Cosmic rays encourage cloud formation, by increasing nucleation.
Cloud formation effects the hydrological cycle, by changing albedo and precipitation.
The hydrological cycle drives CO2 levels, by regulating CO2 sequestration by land plants.

So CO2, humidity, and albedo are all increasingly direct feedbacks from cosmic ray abundance.

Even if we accept this model for the Phanerozoic, it still doesn’t tell us anything about 21st century climate change, for the following reason:
It assumes that CO2 is a passive positive feedback- an amplifier of humidity and/or precipitation.
The problem is that we know the current CO2 increase is NOT due to a feedback; it is due to fossil fuel burning. Therefore, we are already operating outside of the Veizen model. Since his model assumes that CO2 reacts passively, this model cannot be used for predicting the results of a forced change on CO2 content, which is our current situation.

As for the presentation, the only really deceptive bit was when he said that the 1 W/m2 dry CO2 forcing was equivalent to the 1 W/m2 variation in solar irradiance. As realclimate people have occasionally pointed out, the CO2 acts on surface area, which for a sphere is 4 times the cross section (4pi*r2 vs pi*r2). So using W/m2 on effects that operate over different numbers of square meters is dishonest. Interestingly, none of the 60 or so professional geoscientists in the audience called him on this.

The main criticism of the talk from our paleoclimate people was that he showed a lot of correlations of normalized, detrended data where his residual wiggles were way smaller than the magnitude of the detrending. For example, he showed a 1 per mil d18O curve without mentioning that the detrending removed 10 per mil of change.

My main problem was the lack of quantification of processes. For example, he was very coy about how much longer (or shorter) it took a cloud to nucleate in a high radiation vs. low radiation environment. Is it seconds, or hours, or years?

Furthermore, he did not discuss the magnitudes of changes that he claimed to observe on different timescales. For example, his observations on the 100 Ma timescale had 10 degree changes, while his observations on the century and decadal timescale were a degree or less. He correlated these with cosmic ray wiggles, but the magnitude of those cosmic wiggles on the various timescales was not linked to the magnitude of the climactic changes.

Finally, he failed to address any of the non-CO2 alternative hypotheses generally invoked to explain long term changes in paleoclimate. In order to get a new theory accepted, it is generally necessary to find a flaw in the current state of knowledge. He never mentioned the effect of traditional long timescale climate drivers like tectonics.

It was an interesting theory, and one worth trying to quantify, but running to the New York Times might have been a little bit premature.

Monday, November 06, 2006

Survivor: Laboratory

A while ago, a bunch of science promoters were suggesting that perhaps Hollywood should fund an LA Lab style TV drama, where hot, fit, lab scientists went out and solved the mysteries of the universe in ways that were way more exciting, dramatic, and tangible than real science is. The idea was to make science as misrepresented as law or medicine, when it came to television/ real world dissonance.

I think these suggestions are too high-brow. I think instead, they should redefine the common denominator with Survivor: Laboratory. Instead of an exotic jungle with silly adventure camp stunts thrown in, this would be rows of benches, test tubes, and occasionally combustible chemicals. Each team who first successfully synthesizes the correct compound gets immunity. Every show, the most triple thumbed, block-headed, OSHA hazard would get voted off. The protocol is repeated until there is only one survivor, who wins a 4 year scholarship to whatever school they can get into.

Like the current survivor, the show would be dominated not by the chemical/mechanical theory, but by the scheming, double crossing, and sabotaging that generates the most human interest. In this way, it would be very similar to actual professional scientific research. In fact, there could even be an episode where the teams have to crawl through a lab window and an obstacle course of dangerous glassware to steal Rosalind Franklin’s X-ray diffraction patterns.

Such a TV show could be relatively cheap to produce, entertaining, educational, and almost impossible to market. But those constraints didn’t stop Firefly or Operatunity, did they?

Friday, November 03, 2006

Vegemites are terrorists

According to various News Limited papers and websites, US Customs officials have banned the importation of vegemite from Australia to the USA. Evidently the reason given is that vegemite contains folate, which under US regulations can only be added to bread or cereal. Adding it to a spread used on bread is evidently a problem. If true (and with News Limited, you never know), then this has grave consequences for the US-Australia relationship.

First of all, why folate? The most well-known property of this substance is that it prevents neural tube defects in developing embryos. Are birth defects now a constitutional right? Wouldn’t a ban on harmful substances, like saturated fat or cane sugar, be more sensible? Or would those infringe on the right to be a fat slob?

Secondly, what about the free trade agreement? At no point during the FTA negotiations last year did anyone mention using FDA technicalities to block the exchange of culturally significant foodstuffs. This looks like protectionism, pure and simple.

Finally, imagine the consequences of the potential trade war that could erupt as a result. Australia could ban peanut butter, on the grounds that it is a potential allergen. It could forbid the import of Dr. Pepper, because that shit is nasty. And if the Australians wanted a truly disproportionate response, they could outlaw the baking of apple pie, as it has been correlated with dangerous levels of mindless militaristic jingoism*.

And that, my friends, would be a tragedy.

* I don’t know what foodstuffs promote thoughtful pacific jingoism, but anyone with a lead is welcome to comment.

Wednesday, November 01, 2006


The daily progress sheet of my nanowrimo bid is here.