Fiat Lux 1: On Fire for Quantum Mechanics

My sailboat's name is the Fiat Lux — "let there be light" in Latin — drawing from both my theological and scientific personae. I sail a Laser, an Olympic class racing dingy, which is an apt boat for a quantum mechanic. The ability to amplify light by stimulating an existing emission process was first predicted by quantum mechanics, then the apparatus to actually do it was built. Laser is really an acronym: Light Amplification by Stimulated Emission of Radiation. The radiation is electromagnetic radiation, not the radioactive radiation.

There's been a smattering of conversation about light production around my house this weekend between sailing the Laser, setting off fireworks and observing fireflies. One of my teen guests wondered how the fire in fire flies was different from the fire in fireworks. All light is not created in quite the same way....though there are some fundamental similarities.

There are really two fires in fireworks, the thermal explosives that send them skyward, and the "rockets red glare" — the glittering burst of color in the sky. The heat from the thermal explosion (usually blackpowder or a similar substance) is what trigger the colors.

If you ever done a flame test, putting a solid substance or a concentrated solution on a wire loop and placing it in a flame to see what color is produced, you've done the same chemistry. The extreme heat excites electrons in an atom or molecule, and as they fall back down to their lowest energy, or ground state, emitting a photon (a bit of light) that just exactly matches the difference in energy between the excited state and the ground state. An orange flame meant you had sodium on the wire, while a violet flame suggested potassium. More properly this technique is called atomic emission spectroscopy.

For atoms the picture you usually see in a high school text of this process is of a ladder, where electrons are shown moving from rung to rung. The larger the distance between the two rungs (or states) the higher the energy of the photon emitted. If the distance corresponds to photons in the visible region, you see a color, otherwise you have to use something fancier to figure out the energy of the photons being released.

Different atoms have different spacings between states and so the colors they emit when heated to high temperatures are likewise different. There are in fact many states, and so many types of photons can be emitted, but few are in the visible region.

If you click here, you can see a simulation of the photons you'd expect to see when an excited sodium atom returns to the ground state. Are you surprised that sodium can be used for yellow-orange in fireworks? Some urban legends suggest that lead (or radioactive barium) are used in fireworks, but if you look at the line spectrum of lead you can see why it can't be true -- there is no rung to rung jump in lead that corresponds to a visible photon. So a lead firework would be invisible! (Lead used to be used to make the fireworks "crackle"...)

(And it's true that barium salts are used in fireworks, but they are not radioactive. There are no naturally occurring radioactive isotopes of barium.)

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Read more:

An article at C&E News on the chemistry of fireworks

Related posts:

Jello lasers
Romancing the stone (lasers in the plot line of a romance novel)

Image from Wikimedia.

Warning, Dr. Smith! Warning!

An SF fan from the moment I discovered Heinlein's Have Spacesuit -Will Travel in the minuscule public library in the small (population 2500) Midwest town I grew up in, it's probably not a surprise that I would have been an avid watcher of SF on TV. When I get various 'urgent warnings' in my inbox, I often hear the Lost in Space robot's voice in my head, "Warning, Dr. Smith! Warning!"

A few days ago, this warning about the dangers of taking business cards from strangers appeared. Take one of these drug laden cards in your bare hands and soon you will be easy prey for swindlers and worse. Is such a thing possible? Can you be drugged against your will by briefly touching a drug?

In principle, yes. Unbroken skin, though a good way of keeping your insides in, is not an absolute barrier to molecules entering the body. Some molecules — such as DMSO — are better at getting in than others.

When I teach mathematical modeling, one topic we look at is ways to model diffusion. An application that many of my students find interesting are passive drug delivery systems that capitalize on diffusion. In other words - patches. To me this warning sounds like a folkloric riff on drug patches. In fact, delivery through a patch is a pretty complex system, it's not just a matter of soaking the equivalent of a gauze pad in a drug and taping it to your arm.

The drug cocktail purported to be on the business cards is burundanga - a mixture of two plant alkaloids, atropine and scopolamine. Both can be administered through the skin, when I had surgery a couple of years ago, the anesthesiologist use a scopolamine patch to manage my post-op nausea. But he didn't hand me a "don't throw up" card to hang onto for a few minutes in pre-op - that patch he applied behind my ear was a marvel of pharmaceutical engineering!

Burundanga has been used criminally but by slipping into a victim's food or drink. Incidental contact with atropine or scopolamine won't incapacitate you — though the prescribing information for the scopolamine patch points out that you should avoid touching the patch and then your eyes - resulting in dilated pupils and blurry vision.

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Scopolamine was used as an amnesia inducing agent during labor and delivery in the 60's. I suspect Betty Draper's halucinations during labor and delivery on Mad Men (The Fog, Season 3, episode 5).

Image is of belladona, from which atropine and scopolamine can be extracted.

Climate Change Skeptics

Paul Krugman has a piece on climate change on his blog at the NY Times. One commenter responds:

"One thing they are "gong" [sic] to do is point out that if the ppm increase in atmospheric CO2 is solely due to man-made combustion of fossil fuels, laws of chemistry and physics have been violated. For every molecule of carbon, two molecules of oxygen are consumed. Therefore, if the rise in CO2 is due to such combustion, then we should observe a decrease in atmospheric O2 by a factor twice as great. I have seen no evidence to suggest that global O2 is decreasing at all." (H. Muhlphart )

Ouch! My response:

No law of chemistry and physics has been violated by assuming that the increasing CO₂ comes from combustion of fossil fuels. The reason no decrease in O₂ is "noticed" is because the loss due to the formation of carbon dioxide is very small compared to the total amount of oxygen. If you increase the amount of CO₂ by 100 ppm (more or less what's predicted in the next 50 years), the decrease in O₂ is from 209,460 ppm to 209,360 ppm. That's the equivalent of being at the top of less than a 30 foot hill. You certainly don't notice any change in the oxygen levels between the basement and second floor of a house, do you?

And I didn't even bother with the notion that carbon dioxide "eats" two oxygen atoms no matter what carbon source you make it from - fossil fuel or respiration. Or that it's one carbon atom to one oxygen molecule. At this level of understanding of the basic science, you are not simply not entitled to an opinion on the matter.

Chemical Urban Legends: pH

What does the p in pH stand for?

The term pH has been in use for more than a century. It is a logarithmic measure of the hydrogen ion concentration ([H+]): pH = -log10[H+]. (Technically, there aren't bare protons (H+) floating around in solutions, but that wasn’t known when pH was introduced!) The original symbol used by Sorensen was p_H⁺.

Theories vary as to the origin of the p - most agree it means power but whether in Latin, French or German, seems in dispute. Thinking it would be either French or Latin as the original paper was published in French, I was surprised to find that it's neither, though the legend is both old and persistent. By 1920, many authors were assuming that it meant “power”, but Jens Norby returned to the original sources and points out that it was the arbitrary choice of the letters p and q for two variables in the work-up of the experimental data. The variable p eventually ends up in the formula arrived at for the concentration of the hydrogen ion.

The modern form pH was introduced in 1920, "as a matter of typographical convenience".

For the full explanation, see Jens G. Norby, The origin and the meaning of the little p in pH, Trends in Biochemical Sciences 25, 36-37 (2000). The illustration is a selection from the original paper: Sorensen, Compt. redn. du Lab. de Carlsberg 8 1-168 (1909).

Open Laboratory 2009

Open Laboratory 2009 - a juried anthology of the best of the science blogosphere from last year has appeared. Edited by scicurious, it's available here. I have a piece in it - a cleaner version of this post on the use of helium to preserve documents. I'm fascinated with the interplay between web and print that ultimately produces this volume.

Want a copy? Order one -- or if you're feeling lucky, de-lurk and leave a comment before March 5th and I'll draw a winner at random. The rest of the pieces look great - on everything from the flu to charismatic megafauna (whales and chimps) to the statistics of human milk production.

Nobel Conversations

I vividly remember the first time I met a Nobel Prize winner. I was a graduate student in my 3rd year, and Roald Hoffman had recently won the Prize in chemistry (1981). A group of us went up with our research advisor (who had worked with Hoffman as an undergraduate) to hear him speak at a symposium at USC. On the drive up we were briefed as to behavior - do not speak unless spoken to. Frankly, we were happy enough to be out of the lab as well as treated to lunch (and to a terrific speaker). Lunch was at picnic tables in an outdoor courtyard - the grad students all clustered at a table on the edge. Imagine our surprise (and delight) when Hoffman joined us at the table, and spent lunch asking us what we were doing for research, and what excited us most about chemistry. I, at least, left with the sense that I was an interesting part of the chemical community -- even if a very junior one.

The Noble organization and Honeywell are offering the opportunity to anyone to ask a question of Nobel winners. The next live broadcast is Tuesday, March 2 at 11:15am (-6hrs GMT), when you can hear Robert Grubbs, who won the chemistry prize in 2005 for his discovery of olefin metathesis (a method to rearrange carbon-carbon double bonds using metal catalysts). I wrote my oral exam proposal on olefin metathesis in 1982 - I was fascinated then, and am still, with these atomic level architectural changes.

The best part? You can ask questions - email them to question@honeywellscience.com or go through Twitter or Facebook.

Are scientists palatable?

In the early part of the 19th century, the word scientist had yet to be coined. As the scope of materials and phenomena that natural philosophers and historians dealt with increased, there was a growing sense that these terms were inadequate to describing the task of this new breed of inquirers. In the 1830s, the British Association for the Advancement of Science explored potential candidates, but ultimately rejected various proposed terms, including scientist:

"Philosophers was felt to be too wide and too lofty a term,..; savans was rather assuming,..; some ingenious gentleman proposed that, by analogy with artist, they might form scientist, and added that there could be no scruple in making free with this termination when we have such words as sciolist, economist, and atheist — but this was not generally palatable."

The need remained, however, and a decade later, William Whewell, a philosopher and biologist pushed the issue again: “We need very much a name to describe a cultivator of science in general. I should incline to call him a Scientist.” This time it stuck.

Once the name stuck, an image quickly became attached -- wild hair, lab coats and odd apparatus all became part and parcel of what it means to be a scientist. My most recent Thesis columnin Nature Chemistry -- Men of Mystery -- takes up popular images of scientists, and considers the impact the images might have on public discourse about science.

UPDATED: See Snail's Tails post about philosophy and philosophical instruments. The ad for the "philosophical instrument makers" is fascinating!

Science blogging at its best: Open Laboratory 2009

In 2006, Bora Zivkovic brought us the first edition of Open Laboratory, a print collection of the best science blogging of the year. Now in its 4th year, the 2009 edition, guest edited by scicurious at Neurotopia is going to press soon. A record 760 posts were nominated, winnowed down to fifty by scicurious and her panel of judges.

One post of mine (The Pressure to Preserve) will be included! While you're waiting for this edition to come out, I heartily recommend browsing the earlier editions. Who says scientists can't write?

Chemistry on Holiday: Science Cookies

'tis the season for baking on the home front. It's been mostly biologically based leavening (yeast) at my house, but some strictly chemical rising has been going on as well. For an interesting mix of chemistry and biology in the kitchen check out Not So Humble Pie's science cookies: zebrafish, drosophila, gel electrophoresis and atoms are on the menu. Something to keep in mind for the next snow day around here...

Unfortunate Acronyms: PUS

When I was lecturing on lasers this week, I was surprised to discover how many of my students were unaware that laser was an acronym (Light Amplification by Stimulated Emission of Radiation). Science is replete with acronyms - Ira Levine once essayed that if you knew enough acronyms you could pretend you knew computational chemistry - good, bad, really funny and occasionally unfortunate.

On my desk is a paper which refers (with as near as I can tell with a straight face) to "PUS research." Public Understanding of Science. I swear this is true.

If you've got a favorite one - funny, famous or truly unfortunate - leave it in the comments for all of us to enjoy...

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Related Posts
Science in the kitchen: Jello lasers
Romancing the stone (steampunk lit and lasers)