Category: Chemistry

A Sublime Moment

On By rolcottIn Chemistry, Physics: Entropy and Thermodynamics, Uncategorized1 Comment

It’s either late Winter or early Spring, trying to make up its mind. Either way, today’s lakeside walk is calm until I get to the parking lot and there he is, all bundled up and glaring at a huge pile of snow. “Morning, Mr Feder. You look even more out of sorts than usual. Why so irate?”

“The city’s dump truck buried my car in that stuff.”

“Your car’s under that? But there’s a sign saying not to park in that spot when there’s a snow event.”

“Yeah, yeah. Back on Fort Lee we figure the city just puts up signs like that to remind us we pay taxes. I’ll park where I want to. Freedom!”

“I’m beginning to understand you better, Mr Feder. Got a spare shovel? I can help you dig out.”

“My car shovel’s in the car, of course. I got another one at home for the sidewalk.”

I notice something, move over for a better view. “Step over here and look close just above the top of the pile where the sunlight’s hitting it.”

“Smoke! My car’s burning up under there!”

“No, no, something much more interesting. You’re looking at something that I’ve seen only a couple of times so you’re a lucky man. That’s steam, or it would be steam at a slightly higher temperature. What you’re looking at is distilled snow. See the sparkles from ice crystals in that cloud? Beautiful. Takes a very special set of circumstances to make that happen.”

“I’d rather be lucky in the casino. What’s so special?”

“The air has to be still, absolutely no breeze to sweep floating water molecules away from the pile. Temperature below freezing but not too much. Humidity at the saturation point for that temperature. Bright sun shining on snow that’s a bit dirty.”

“Dirty’s good?”

“In this case. Here’s the sequence. Snow is water molecules locked into a crystalline structure, right? Most of them are bonded to neighbors top, bottom and every direction. The molecules on the surface don’t have as many neighbors, right, so they’re not bonded as tightly. So along comes sunlight, not only visible light but also infrared radiation—”

“Infrared’s light, too?”

“Mm-hm, just colors we can’t see. Turns out because of quantum, infrared light photons are even more effective than visible light photons when it comes to breaking water molecules away from their neighbors. So a top molecule, I’ll call it Topper, escapes its snow crystal to float around in the air. Going from solid directly to free-floating gas molecules, we call that sublimation. Going the other way is deposition. Humidity’s at saturation, right, so pretty soon Topper runs into another water molecule and they bond together.”

<sarcasm, laid on heavily> “And they make a cute little snow crystal.”

“Not so fast. With only two molecules in the structure, you can’t call it either solid or liquid but it does grow by adding on more molecules. Thing is, every molecule they encounter gives up some heat energy as it ties down. If the weather’s colder than it is here, that’s not enough to overcome the surrounding chill. The blob winds up solid, falls back down onto the pile. If it’s just a tad warmer you get a liquid blob that warms the sphere of air around it just enough to float gently upwards—”

“Like a balloon, I got the picture.”

“Floats up briefly. It doesn’t get up far before the surrounding chill draws out that heat and wins again. Not so brief when there’s a little dirt in there.”

“The dirt floats?”

“Of course not. The dirt’s down in the snow pile, but it’s dark and absorbs more sunlight energy than snow crystals do. What the dirt does is, it tilts the playing field. Heat coming from the dirt particles increases the molecular break‑free rate and there’s more blobs. It also warms the air around the blobs and floats them high enough to form this sparkling cloud we can see and enjoy.”

“You can enjoy it. I’m seeing my car all covered over and that’s not improving my mood.”

“Better head home for that shovel, Mr Feder. The snow dumper’s coming back with another load.”

~ Rich Olcott

Deep Dive

On By rolcottIn Chemistry, Physics: Entropy and Thermodynamics, UncategorizedLeave a comment

“Sy, I’m trying to get my head wrapped around how the potential‑kinetic energy thing connects with your enthalpy thing.”

“Alright, Vinnie, what’s your cut so far?”

“It has to do with scale. Big things, like us and planets, we can see things moving and so we know they got kinetic energy. If they’re not moving steady in a straight line we know they’re swapping kinetic energy, give and take, with some kind of potential energy, probably gravity or electromagnetic. Gravity pulls things into a circle unless angular momentum gets in the way. How’m I doing so far?”

“I’d tweak that a little, but nothing to argue with. Keep at it.”

“Yeah, I know the moving is relative to whether we’re in the same reference frame and all that. Beside the point, gimme a break. So anyway, down to the quantum level. Here you say heat makes the molecules waggle so that’s kinetic energy. What’s potential energy like down there?”

<grabs another paper napkin> “Here’s a quick sketch of the major patterns.”

“Hmm. You give up potential energy when you fall and gravity’s graph goes down from zero to more negative forever, I guess, so gravity’s always attracting.”

“Pretty much, but at this level we don’t have to bother with gravity at all. It’s about a factor of 1038 weaker than electric interactions. Molecular motions are dominated by electromagnetic fields. Some are from a molecule’s other internal components, some from whatever’s around that brandishes a charge. We’ve got two basic patterns. One of them, I’m labeling it ‘Waggle,’ works like a pendulum, sweeping up and down that U‑shape around some minimum position, high kinetic energy where the potential energy’s lowest and vice‑versa. You know how water’s H‑O‑H molecules have that the V‑shape?”

“Yeah, me you and Eddie talked about that once.”

“Mm‑hm. Well, the V‑shape gives that molecule three different ways to waggle. One’s like breathing, both sides out then both sides in. If the hydrogens move too far from the oxygen, that stretches their chemical bonds and increases their potential energy so they turn around and go back. If they get too close, same thing. Bond strength is about the depth of the U. The poor hydrogens just stretch in and out eternally, swinging up and down that symmetric curve.”

“Awww.”

“That’s a chemist’s picture. The physics picture is cloudier. In the quantum version, over here’s a trio of fuzzy quarks whirling around each other to make a proton. Over there’s a slightly different fuzzy trio pirouetting as a neutron. Sixteen of those roiling about make up the oxygen nucleus plus two more for the hydrogens plus all their electrons — imagine a swarm of gnats. On the average the oxygen cloud and the two hydrogen clouds configure near the minimum of that U‑shaped potential curve but there’s a lot of drifting that looks like symmetrical breathing.”

“What about the other two waggles?”

“I knew you’d ask. One’s like the two sides of a teeterboard, oscillating in and out asymmetrically. The other’s a twist, one side coming toward you and then the other side. Each waggle has its own distinct set of resistance forces that define its own version of waggle curve. Each kind interacts with different wavelengths of infrared light which is how we even know about them. Waggle’s official name is ‘harmonic oscillator.’ More complicated molecules have lots of them.”

“What’s that ‘bounce’ curve about?”

“Officially that’s a Lennard-Jones potential, the simplest version of a whole family of curves for modeling how molecules bounce off each other. Little or no interaction at large distances, serious repulson if two clouds get too close, and a little stickiness at some sweet-spot distance. If it weren’t for the stickiness, the Ideal Gas Law would work even better than it does. So has your head wrapped better?”

“Sorta. From what I’ve seen, enthalpy’s PV part doesn’t apply in quantum. The heat capacity part comes from your waggles which is kinetic energy even if it’s clouds moving. Coming the other way, quantum potential energy becomes enthalpy’s chemical part with breaking and making chemical bonds. Did I bridge the gap?”

“Mostly, if you insist on avoiding equations.”

~ Rich Olcott

Early Days in The Sunshine

On By rolcottIn Chemistry, Physics: Entropy and Thermodynamics, Uncategorized1 Comment

“Wait, Sy. From what you just said about rocket fuel, its enthalpic energy content changes if I move it. On the ground it’s ‘chemical energy plus thermal plus Pressure times Volume.’ Up in space, though, the pressure part’s zero. So how come the CRC Handbook people decided it’s worthwhile to publish pages and pages of specific heat and enthalpy tables if it’s all ‘it depends’?”

“We know the dependencies, Vinnie. The numbers cover a wide temperature range but they’re all at atmospheric pressure. ‘Pressure times Volume‘ makes it easy to adjust for pressure change — just do that multiplication and add the result to the other terms. It’s trickier when the pressure varies between here and there but we’ve got math to handle that. The ‘thermal‘ part’s also not a big problem because if you something’s specific heat you know how its energy content changes with temperature change and vice‑versa.”

<checking a chart on his phone> “This says water’s specific heat number changes with temperature. They’re all about 1.0 but some are a little higher and some a little lower. Graph ’em out, looks like there’s a pattern there.”

<tapping on Old Reliable’s screen> “Good eye. High at the extreme temperatures, lower near — that’s interesting.”

Data from CRC handbook, 39th Ed, pp 2081-2082

“What’s that?”

“The range where the curve is flattest, 35 to 40°C. Sound familiar?”

“Yeah, my usual body temperature’s in there, toward the high side if I’ve got a fever. What’s that mean?”

“That’s so far out of my field all I’ve got is guesses. Hold on … there, I’ve added a line for 1/SH.”

“What’s that get you?”

“A different perspective. Specific Heat is the energy change when one gram of something changes temperature by one degree. This new line, I’ve called it Sensitivity, is how many degrees one unit of heat energy will warm the gram. Interesting that both curves flatten out in exactly the temperature range that mammals like us try to maintain. The question is, why do mammals prefer that range?”

“And your answer is?”

“A guess. Remember, I’m not a biologist or a biochemist and I haven’t studied how biomolecules interact with water.”

“I get that we should file this under Crazy Theories. Out with it.”

“Okay. Suppose it’s early days in mammalian evolution. You’re one of those early beasties. You’re not cold-blooded like a reptile, you’re equipped with a thermostat for your warm blood. Maybe you shiver if you’re cold, pant if you’re hot, doesn’t matter. What does matter is, your thermostat has a target temperature. Suppose your target’s on the graph’s coolish left side where water’s sensitivity rises rapidly. You’re sunning yourself on a flat rock, all parts of you getting the same calories per hour.”

“That’s on the sunward side. Shady side not so much.”

“Good point. I’ll get to that. On the sunward side you’re absorbing energy and getting warm, but the warmer you get the more your heat sensitivity rises. Near your target point your tissues warm up say 0.4 degree per unit of sunlight, but after some warming those tissues are heating by 0.6 degrees for the same energy input.”

“I recognize positive feedback when I see it, Sy. Every minute on that rock drives me further away from my target temperature. Whoa! But on the shady side I don’t have that problem.”

“That’s even messier. You’ve got a temperature disparity between the two sides and it’s increasing. Can your primitive circulatory system handle that? Suppose you’re smart enough to scurry out of the sunlight. You’ve still got a problem. There’s more to you than your skin. You’ve got muscles and those muscles have cells and those cells do biochemistry. Every chemical reaction inside you gives off at least a little heat for more positive feedback.”

“What if my thermostat’s set over there on the hot side?”

“You’d be happy in the daytime but you’d have a problem at night. For every degree you chill below comfortable, you need to generate a greater amount of energy to get back up to your target setting.”

“Smart of evolution to set my thermostat where water’s specific heat changes least with temperature.”

“That’s my guess.”

~~ Rich Olcott

It’s in The Book

On By rolcottIn Chemistry, Physics: Entropy and Thermodynamics, Physics: Quantum Mechanics, UncategorizedLeave a comment

A young man’s knock, eager yet a bit hesitant. “Door’s open, Jeremy, c’mon in.”

“Hi, Mr Moire, I’ve got something to show you. It’s from my acheii, my grandfather. He said he didn’t need it any more now he’s retired so he gave it to me. What do you think?”

“Wow, the CRC Handbook of Chemistry And Physics, in the old format, not the 8½×11″ monster. An achievement award, too — my congratulations to your grandfather. Let’s see … over 3000 pages, and that real thin paper you can read through. It’s still got the math tables in front — they moved those to an Appendix by the time I bought my copy. Oooh yeah, lots of data in here, probably represents millions of grad student lab hours. Tech staff, too. And then their bosses spent time checking the work before publishing.”

“Acheii said I’d have to learn a lot before I could use it properly. I see lots of words in there I don’t recognize.” <opens book to a random page> “See, five- and six‑figure values for, what’re Specific Heat and Enthalpy?”

“Your grandfather’s absolutely correct. Much of the data’s extremely specialized. Most techs, including me, have a few personal‑favorite sections they use a lot, never touch the rest of the book. These particular pages, for instance, would be gold for a someone who designs or operates steam‑driven equipment.”

“But what do these numbers mean?”

“Specific Heat is the amount of heat energy you need to put into a certain mass of something in order to raise its temperature by a certain amount. In the early days the Brits, the Scots really, defined the British Thermal Unit as the amount of energy it took to raise the temperature of one pound of liquid water by one degree Fahrenheit. You’d calculate a fuel purchase according to how many BTUs you’d need. Science work these days is metric so these pages tabulate Specific Heat for a substance in joules per gram per °C. Tech in the field moves slow so BTUs are still popular inside the USA and outside the lab.”

“But these tables show different numbers for different temperatures and they’re all for water. Why water? Why isn’t the Specific Heat the same number for every temperature?”

“Water’s important because most power systems use steam or liquid water as the working fluid or coolant. Explaining why heat capacity varies with temperature was one of the triumphs of 19th‑century science. Turns out it’s all about how atomic motion but atoms were a controversial topic at the time. Ostwald, for instance—”

“Who?”

“Wilhelm Ostwald, one of science’s Big Names in the late 1800s. Chemistry back then was mostly about natural product analysis and seeing what reacted with what. Ostwald put his resources into studying chemical processes themselves, things like crystallization and catalysis. He’s regarded as the founder of Physical Chemistry. Even though he invented the mole he steadfastly maintained that atoms and molecules were nothing more than diffraction‑generated illusions. He liked a different theory but that one didn’t work out.”

“Too bad for him.”

“Oh, he won the first Nobel Prize in Chemistry so no problem. Anyway, back to Specific Heat. In terms of its molecules, how do you raise something’s temperature?”

“Um, temperature’s average kinetic energy, so I’d just make the molecules move faster.”

“Well said, except in the quantum world there’s another option. The molecules can’t just waggle any which way. There are rules. Different molecules do different waggles. Some kinds of motion take more energy to excite than others do. Rule 1 is that the high‑energy waggles don’t get to play until the low‑energy ones are engaged. Raising the temperature is a matter of activating more of the high‑energy waggles. Make sense?”

“Like electron shells in an atom, right? Filling the lowest‑energy shells first unless a photon supplies more energy?”

“Exactly, except we’re talking atoms moving within a molecule. Smaller energies, by a factor of 100 or more. My point is, the heat capacity of a substance depends on which waggles activate as the temperature rises. We didn’t understand heat capacity until we applied quantum thinking to the waggles.”

“What about ‘Enthalpy’ then?”

Crystal photo by JJ Harrison

~ Rich Olcott

The Oldest Clock Ticks Slowest

On By rolcottIn Astronomy: Techniques, Chemistry, UncategorizedLeave a comment

<Cliff‑hanger Cathleen strikes again> “How can you even measure a 2‑million year half‑life?”

Kareem’s right back at her. “What’s a half‑life?”

“Start a clock, weigh a sample, wait around for a while and then weigh it again to see how much is still there. When half of it’s gone, stop the clock and you’ve measured a half‑life. Simple.”

“Simple but not that simple or maybe a bit simpler. For one thing, you don’t have to wait for a full half‑life. For spontaneous radioactivity, all you have to know is the interval and whatever fraction disappeared. There’s a nice equation that ties those two to the half‑life.”

“Spontaneous? Like there’s another kind?”

“Stimulated radioactivity. That’s what nuclear reactors do — spew neutrons at uranium‑235 atoms, for instance, transmuting them to uranium‑236 so they’ll split into krypton and barium atoms and release energy and more neutrons. How often that happens depends on neutron concentration. Without that provoking push, the uranium nuclei would just split when they felt like it and that’s the natural half‑life.”

“Wait. I know that curve, it’s an exponential. Why isn’t e in the equation?”

“It could be. Would you prefer e-0.69315*t/half‑life? Works just as well but it’s clumsier. Base‑2 makes more sense when you’re talking halves. Usually when you say ‘exponential’ people visualize an increase. Here we’re looking at a decrease by a constant percentage rate but yeah, that’s an exponential, too. You get a falling curve like that from a Geiger counter and you’re watching counts per minute from someone’s thyroid that’s been treated with iodine‑131. Its 8‑day half‑life is slow enough to track that way. Really short half‑lives I don’t know much about; I care about the slow disintegraters that are either primordial or generated by some process.”

“Primordial — that means ‘back to the beginning’, which in your specialty would mean the beginning of the Solar System. We’re pretty sure the Sun’s pre‑planetary disk was built from dust broadcast by stars that went nova. Isotopes in the dust must be the primordial isotopes, right? Which ones are the other kind?”

“Mmm, aluminum‑26 is a good example. The half‑life equation still applies even for million‑year intervals. Half‑life of aluminum‑26 is about 0.7 million years and it decays to magnesium‑26. Whatever amount got here from the stars would have burnt down to a trillionth of that within the first 30 million years or so after arrival. Any aluminum‑26 we find today couldn’t be primordial. On the other hand, cosmic rays can smack a proton and neutron out of a silicon‑28 nucleus and voila! a new aluminum‑26. There’s a steady rain of cosmic rays out in space so there’s a steady production of aluminum‑26 out there. Not here on Earth, though, because our atmosphere blocks out most of the rays. Very nice for us geologists who can compare measured aluminum‑26 to excess magnesium‑26 to determine when a meteorite fell.”

“Excess?”

“Background magnesium is about 10% magnesium‑26 so we have subtract that to get the increment which came from aluminum‑26. A lot of the arguments in our field hinge on how much of which isotope is background or was background when a given rock formed. That’s one reason you see so much press about tiny but rugged zircons. They’re key to uranium‑lead dating. Crystallizing zirconium silicate doesn’t allow lead ions into its structure but it happily incorporates uranium ions. Uranium‑235 and uranium‑238 both decay to crystal‑trapped lead, but each isotope goes to a different lead isotope and with a different half‑life. The arithmetic’s simpler and the results are more definitive when you know that the initial lead content was zero.”

“So that aluminum‑magnesium trick’s not your only tool?”

“Hardly. The nuclear chemists have given us a long list of isotope chains, what decays to what with what half‑life and how much energy the radiating particle gets. Nuclei flit between quantum energy levels just like atoms and molecules do, except a spectrum of alpha or beta particles is a different game from the light‑wave spectrum. Tell me a radiated particle’s energy and I can probably tell you which isotope spat it out and disappeared.”

“Your ladder rungs are Cheshire Cat grins.”

~~ Rich Olcott

The Ideal Gas Game

On By rolcottIn Astronomy: Planetary Science, Chemistry, Physics: Fundamentals, UncategorizedLeave a comment

“But Uncle Sy, you never did answer my real question!”

“What question was that, Teena?”

“About the helium planet. With oxygen. Oh, I guess I never did get around to asking that part of it. You side‑tracked us into how a helium‑oxygen atmosphere would be unstable unless it was really cold or the planet had more gravity than Earth so the helium wouldn’t fly away. But what I wanted to know was, what would it be like before the helium left? Like, could we fly a plane there?”

“Mmm, let’s get a leetle more specific. You asked about swapping all of Earth’s atmospheric nitrogen with helium. Was that one helium atom for each nitrogen molecule or each nitrogen atom?”

“What difference would that make?”

“Mass, to begin with. A helium atom weighs about 1/3 of a nitrogen atom, 1/7 of a nitrogen molecule. The atmospheric pressure we feel is the weight of all the air molecules above us. Swap out 80% of those molecules for something lighter, pressure goes down whether we swap helium for molecules or helium for atoms. We could calculate either one. But the change would be much harder to calculate for the atom‑for‑atom swap.”

“Why?”

“Mmm, have you gotten into equations yet in school?”

“You mean algebra, like 3x+7=8x+2? Yeah, they’re super‑easy.”

“This won’t even be as complicated as that. Here’s a famous Physics equation called The Ideal Gas Law — PV=nRT. Each letter stands for one quantity. Two adjacent quantities are multiplied together, okay? The pressure in a container is P, the container’s volume is V, T is the absolute temperature, and n is a measure of how much gas is in there.”

“You skipped R.”

“Yes, I did. It’s a constant number. Its job is to make all the units come out right. For instance, if the pressure’s in atmospheres, the volume’s in liters, n is in grams of helium and the temperature is in kelvins, then R is 0.021. Suppose you’re holding a balloon filled with helium and it’s at room temperature. What can you say about the gas?”

“Umm, all the nRT stuff doesn’t change so P times V, whatever it is, doesn’t change either.”

“If we let it fly upward until the pressure was only half what it is here…?”

“Then V would double. The balloon would get twice as big. Unless it burst, right?”

“You got the idea. Okay, now let’s fiddle with the right-hand side. Suppose we double the amount of helium.”

“P times V must get bigger but we don’t know which one.”

“Why not both?”

“Wooo… Each one could get some bigger… Oh, wait, I’m holding the balloon so the pressure’s not going to change so the balloon gets twice bigger.”

“Good thinking. One more thing and we can get back to your difference question. The Ideal Gas Law doesn’t care what kind of gas you’re working with. All the n quantity really cares about is how many particles are in the gas. A particle can be anything that moves about independently of anything else — helium atom or nitrogen molecule, doesn’t matter. If you change the definition of what n is measuring, all that happens is you have to adjust R so the units come out right. Then the equation works fine. Next step—”

“Wait, Uncle Sy, I want to think this atom‑or‑molecule thing through for myself. I’m gonna ignore R times T because both of them stay the same. So if we swap one atom of helium for one molecule of nitrogen, the number of particles doesn’t change and PV doesn’t change. But if we swap one atom of helium for each atom of nitrogen then n doubles and so does PV. But if we do that for the whole atmosphere then we can’t say that the pressure won’t change because the atmosphere could just expand and that’s the V but the pressures are all different as you go higher up anyway. Oh, wait, T changes, too, because it’s cold up there. It’s complicated, isn’t it?”

“It certainly is. Can we stick to just the simple atom‑for‑molecule swap?”

“Uh‑huh.”

~~ Rich Olcott

  • Thanks again, Xander, and happy birthday. Your question was deeper than I thought.

A Fleeting Shadowed Sky

On By rolcottIn Astronomy: Planetary Science, Chemistry, UncategorizedLeave a comment

“Hey, Uncle Sy, I’ve got a what‑if for you.”

“What’s that, Teena?”

“Suppose we switched Earth’s air molecules with helium. No, wait, except for the oxygen molecules. I know we need them.”

“First off, a helium-oxygen atmosphere wouldn’t last very long, not on the geological time scale. That’s an unstable situation.”

“Why, would the helium burn up like I’ve seen hydrogen do?”

“No, helium doesn’t burn. Helium atoms are smug. They’re happy with exactly the electrons they have. They don’t give, take or share electrons with oxygen or anything else. No, the issue is that helium’s so light.”

“What difference does that make?”

“The oxygen and helium won’t stay mixed together.”

“The air’s oxygen and nitrogen molecules are all mixed together. They told us that in Science class.”

“That’s correct. But oxygen and nitrogen molecules weigh nearly the same. It would take eight balloon‑fulls of helium to match the weight of one balloon‑full of oxygens. Suppose you had a bunch of equal‑weighted marbles, say red ones and blue ones. Pretend you pour them into a big bucket and stir them around like an atmosphere does. Which color would wind up on top?”

“Both, they’d stay mixed together.”

“Uh-huh. Now replace the blue marbles with marble‑sized ping‑pong balls and stir well.”

“The heavy marbles slide to the bottom. The light balls need to be somewhere so they get bullied up to the top.”

“Exactly. That’s what the oxygen molecules would do — sink down toward the ground and shove the helium atoms up to the top of the atmosphere. Funny thing though — the shoving happens faster than the sinking.”

“Why’s that?”

“It’s the mass thing again. At any given temperature, helium atoms in a gas zip around four times faster than oxygen molecules do. Anyway, the helium atoms that arrive up top won’t stay there.”

“Where else would they go?”

“Anywhere else, basically. Have you heard the phrase, ‘escape velocity‘?”

“It has something to do with rockets, doesn’t it?”

“Well, them, too. The general idea is that once you reach a certain threshold speed relative to a planet or something, you’re going too fast for its gravity to pull you back down. There’s a formula for calculating the speed. The fun thing is, the speed depends on the mass of what you’re escaping from and your distance from the object’s center, but it doesn’t depend on your own mass. It applies to everything from rockets to gas molecules.”

“And we were just talking about helium being zippy. Is it zippy enough to escape Earth?”

Chart by Cmglee, licensed under
CCA-SA 3.0 Unported

“Good thinking! That’s exactly where I was going. The answer is, ‘Maybe.’ It depends on temperature. Warm molecules are zippy, cold molecules not so much. At the same temperature, light molecules are zippier than heavy ones. There’s a chart that shows thresholds for different molecules escaping from different planets. Earth could hold onto its helium atoms, but only if our atmosphere were more than a hundred degrees colder than it is. Warm as we are, bye‑bye helium.”

“How long would that take?”

“That’s a complicated question with lots of ‘It depends’ in the answer. Probably the most important has to do with water.”

“I didn’t say anything about water, just helium and oxygen.”

“I know, but much of Earth’s weather is driven by water vaporizing or condensing or just carrying heat from place to place. Water‑powered hurricanes and even big thunderstorms stir up the atmosphere enough to swoosh helium up to bye‑bye territory. On the other hand, suppose our helium‑Earth is dry. The atmosphere’s layers would be mostly stable, light atoms would be slow to rise. We’d have a very odd‑looking sky.”

“No clouds.”

“Pretty much. But it wouldn’t be blue, either.”

“Would it be pink? I like pink.”

“Sorry, sweetie, it’d be dark dark blue, some lighter near the horizon. Light going past an atomic or molecular particle can scatter from its temporarily distorted electron cloud. Nitrogen and oxygen molecules distort more easily than helium atoms do. Earth skies are blue thanks to sunlight scattered by oxygen and nitrogen. Helium skies wouldn’t have much of that.”

~ Rich Olcott

  • Thanks again to Xander, who asked a really good helium question.

Sounds, Harsh And Informative

On By rolcottIn Astronomy: Techniques, Chemistry, Physics: Waves, UncategorizedLeave a comment

Vinnie’s frowning. “Wait, Sy. I get how molecules bumping into each other can carry a sound wave across space if the frequency’s low enough and that can maybe account for galaxies having spiral arms. So what’s that got to do with the Sonication Project?”

Now Jeremy’s frowning. “What’s sonication got to do with Astronomy? One of my girl friends uses sonication in Biology lab when she’s studying metabolism in plant cells.”

“Whoa! Sonification, not sonication — they could have called it soundify‑cation but sonification‘s classier. ‘Sonication‘ uses high‑intensity ultrasound to jiggle a sample so roughly that cell walls can’t take the stress. They break open and spill the cell’s internal soup out where your friend’s probes can get to it. Tammy, the chemist down the hall from my lab, uses sonication, too.”

“Whoa, Susan, wouldn’t sonication break up molecules?”

“Depends on the frequency and intensity, Vinnie. Sonication can mess up big floppy proteins and DNA, but chemists who play with little peptides and such don’t care. Tammy does solid‑state chemistry. She’s looking for superconductors and she actually does want to break things. The field’s hot category these days is complex copper oxides doped with other metals. You synthesize those compositions by sintering a mix of oxide powders. To maximize contact for a good reaction you need really fine‑grained powders. Sonication does a great job of shattering brittle oxide grains down to bits just a few‑score atoms wide. But Tammy’s technique is even more elegant than that.”

“Elegant sneezes from the powder?”

Susan wallops my shoulder. “No, Sy, the powders are so small they’d be a lung hazard and some of them are toxic. Everything’s done behind respiratory protection.” <Susan doesn’t joke about lab safety.> “There’s evidence that some of these materials are only superconductive if they have the right kind of layered structure. Turns out that if Tammy has her sonicator setup just right when she preps a sample for sintering, the sound wave peaks and valleys inside the machine make the shattered particles settle out in interesting layers.”

“Like Chladni figures.”

“Oh, you know about them.”

“Yeah, I wrote about them a few years ago. Waves do surprising things.”

The Bullet Cluster (1E 0657-56)
Sonification Credit: NASA/CXC/SAO/K.Arcand,
SYSTEM Sounds (M. Russo, A. Santaguida), based on X-Ray image by NASA/CXC/CfA/M.Markevitch,
Optical and lensing map: NASA/STScI, Magellan/U.Arizona/D.Clowe,
Lensing map: ESO WFI

Vinnie’s getting impatient. “So what’s sonification then?”

Tinkly music bursts from Cathleen’s tablet. “This one’s listenable, Susan, and it’s a nice demonstration of what sonification’s about and how arbitrary it can be. You start with complicated multi‑dimensional data and use some process to turn it into audible signals. The process algorithm can use any sound characteristics you like — loudness, pitch, timbre, whatever. This example started with the famous Bullet Cluster image that most people accept as the first direct confirmation of dark matter. All the white‑ish thingies are galaxies except for the ones with pointy artifacts — those are stars. The pink haze is X‑ray light from the same region. The blue haze comes from a point‑by‑point assessment of how badly the galaxy images have been distorted by gravitational lensing — that’s an estimate of the dark matter mass between us and that region of sky. Got all that?”

“And that vertical line is like a scan going across the picture?”

“It’s not like a scan, it is a scan. Imagine a collection of tiny multi‑spectral cameras arranged along a carrier bar. As the bar travels across the picture, each camera emits three signals proportional to the amount of white, pink and blue light it sees. If you look close, just to the right of the line, you’ll see moving white, red and blue line‑charts of the respective signals.”

“That’s fine, but what’s with the sound effects?”

“The Project’s sonification processing generated hiss and rumble sounds whose loudness is proportional to the red and blue signals. Each white‑ish peak became a ping whose pitch indicates position along that bar.”

“Why go to all that trouble?”

“The sounds encode the picture for vision‑challenged people. Beyond that, the Project participants hope that with the right algorithms, their music will reveal things the pictures don’t.”

“They should avoid screamy sounds.”

~~ Rich Olcott

More Map Games

On By rolcottIn Chemistry, General: Fun Stuff, UncategorizedLeave a comment

Vinnie’s not in his usual afternoon spot at the table by the coffee shop door. Then I hear him. “Hey, Sy, over here.” He’s at the center table, surrounded by Cal’s usual clientele but they’re passing sheets of paper around. I worm my way through the crowd. ”What’s going on, Vinnie?”

“Me and Larry are both between piloting assignments so we spent the weekend playing with that map software he bought. He’s figured out how to link it with online databases so we can map just about anything all different ways. Hey, you’re into history, right?”

“Some, yes.”

“This one’s about how far countries go back. I kinda thought countries have always just been there, but no. We found a list of when each country got to have their own government independent of somebody else in charge, so we made this map with the oldest countries the darkest. Look how pale most of the world is. Look at us — the USA is the tenth oldest country. I couldn’t believe it.”

“Ah, I know Denmark started with the Vikings soon after the Roman Empire collapsed. Hungary’s history as a kingdom started about the same time. Then there’s a handful of old states defended by mountains — yup, I see Nepal and Switzerland. Andorra, Liechtenstein and San Marino are in the same category, but they’re too small for this map to show them.”

“You missed the Netherlands from 1579 when they broke free from Spain. No mountains. Larry graphed the numbers down in the corner.”

“Mm-hm. I see two waves. The USA and France started the first one in the late 1700s. That took in most of the New World by the mid‑1800s. Then two World Wars and ‘Katie, bar the door!‘ I hadn’t realized how abruptly de‑colonization took place. Wow. All of Africa and most of southeast Asia became free‑standing countries in just half a century. What’s with Russia — missing data?”

“Gotcha, Sy. That was 1991, when the USSR broke up. Bang! Twenty new countries, all near the top of the scale.” <shuffling papers> “Here’s another one you’ll like. Larry has this theory that countries with lots of neighbors get militarized ’cause they’ve always got a war going on somewhere but if you don’t share borders with hardly anyone, no problem. He did up this map to check his theory. See Canada’s light blue ’cause it’s got only us, we’re dark blue ’cause we got Canada and Mexico. Dark green countries got four and so on. Whaddaya see here?”

“Uh-oh.”

“Yeah. Top of the list, 14 each, are Russia and China who are not best buddies with hardly anybody. Brazil’s got 10, but rainforest is probably as good as mountains.”

“Good point.”

“Excuse me, guys, but I’ve got personal counter‑example experience.”

“Hi, Susan. What’s that?”

“I grew up in Korea, right? Only 2 neighbors, China and Japan, but we’ve got a tough history because each of them just used us as a bridge to get to the other one. Tell Larry it makes a difference who you share a border with.”

“I’ll pass the word. Wait a minute…” <more paper shuffling> “Here’s one we did just for you, Ms Chemist.”

“Weird. How do you even read this?”

“We ran into a problem with the standard maps when we colored each country according to how many chemical elements were discovered there. Most of the action mushed into western Europe’s small area when we showed the other countries. Larry tried a bunch of different projections. This one’s like a fish‑eye lens looking down near the North Pole. See, Russia’s spread around the center but Europe’s bigger?”

“Ah, once I know what to look for it snaps in.”

“I cropped it down to the oval ’cause all the blue sea didn’t fit on the page.”

“Understandable. Lesseee… The UK’s on top mostly because of Wollaston’s geochemistry, Humphry Davy’s work on electropositive metals, and Ramsay isolating the inert gases. The USA owes its second‑place status to Seaborg’s isotope factory at UCal Berkeley. One step down, Germany, France and Sweden ran a discovery horse‑race during the 1800s. Russia came on strong with radioactives but that was late in the game.”

“Wait, Susan. How’d the purples get into this? No big labs there.”

“Except for nihonium, it’s mostly right‑place‑right‑time luck. India gets credit because a French astronomer observing an eclipse from there spotted a helium line in the solar spectrum. Later, an Italian recorded the line on Earth and a Scot isolated the gas.”

~~ Rich Olcott

A Disk of Heat And Violence

On By rolcottIn Astronomy: Planetary Science, Chemistry, UncategorizedLeave a comment

Susan suddenly sits bolt upright. “WOW! Kareem, that Chicxulub meteor that killed off the dinosaurs — paleontologists found iridium from it all over the world, right?”

“Right, the famous K‑T or K‑Pg boundary So?”

“It’d take a lot of iridium to cover the world. Iridium’s deep in the Periodic Table’s Soft Siderophile territory. Iron’s Soft. When Earth was molten, iron would extract and concentrate iridium. That’s why there’s so little iridium in Earth’s crust ’cause it’s all gone to the core. That iridium‑carrying meteorite must have been the iron kind.”

“Probably.”

Vinnie guffaws. “HAW! Earth’s Hard and crunchy on the outside, Soft and chewy in the inside, just like a good cookie.”

“Or an armored knight, from the dragon’s viewpoint. But how did Earth get that way, Cathleen?”

“Long story, Sy. The academics are still arguing about the details.”

“I love a good story, especially if it ends up explaining asteroid Psyche.”

“It starts 4½ billion years ago, when the Solar System was a rotating disk of galactic debris, clouds of hydrogen plus heavier dust and grit spewed out by energetic stars. Some of the atoms in that grit were important, right, Kareem?”

“Yup. Iron and nickel for planetary cores, silicon and oxygen for the crusts, radioactive isotopes of potassium, uranium and thorium but especially the short‑lived radioactives like aluminum‑26. Half‑life for that one’s only a million years.”

Al, Eddie and Vinnie erupt.
 ”If the short‑timers are gone, how come you say they were important?”
  ”How do we know they were even there?”
   ”If it’s such a short‑timer, is that stuff even a thing any more?”

Kareem’s not used to such a barrage but Cathleen’s a seasoned teacher. “Aluminum‑26 definitely is still a thing, because it’s continually produced by cosmic rays colliding with silicon atoms that aren’t too deeply buried. The production rate is so steady that Kareem’s colleagues estimate how long a meteorite was exposed to cosmic rays from its load of aluminum‑26 decay products compared to its related stable isotopes. We know aluminum‑26 was in the early debris because we’ve found its decay products on Earth. We even know how much — about 50 atoms per million stable aluminum atoms.”

Kareem regains his footing. “As to why it’s important, molten silicate droplets in the early system became chondrules when they aggregated to form chondritic meteorites. The droplets couldn’t have stayed that hot just from nuclear fission by their long‑lived radioactives. The short‑timers, especially aluminum‑26, must have supplied the extra heat early on. If short‑timers could keep the droplets molten, they certainly could have kept the newly‑forming planets molten for a while. Being fluid’s important because that’s the only state where Susan’s Hard‑Soft phase separation can happen.”

Cathleen nods. “The radioactives were just part of the story, though. The early system was a chaotic place. Forget notions of everything smoothly whirling around like the rings of Saturn. Except for the biggest objects, the idea of an orbit was just silly. Each object was gravitationally influenced by beaucoodles of other objects of all sizes that didn’t even all go in the same direction. There was crashing, lots of crashing. Every smash‑up converted kinetic energy to heat, lots of heat. Each collision could generate fragments which would cascade on to other collisions, maybe even become meteorites. Large objects would accumulate mass and heat energy in violent mergers with smaller objects. A protoplanet’s atom‑level Hard‑Hard and Soft‑Soft interactions would have plenty of chemical opportunities to assemble cohesive masses rising or sinking through the liquid melt just because of buoyancy and there you’ve got your layers.”

“But collisions didn’t have to be violent, Cathleen. Fragments could hang together through gravity or surface stickiness. That’s how the Bennu and Ryugu rubble pile asteroids formed.”

“Good point, Kareem, and that brings us to Psyche. We know its density is higher than stone but less than iron. The asteroid could be part of a planetoid’s interior, surviving after violent collisions chipped away the surface rock. It could be a rubble pile of loose metallic bits. It could be a mix of metal and rock like the Museum’s pallasite slice. Or an armored shell. We just won’t know until the Psyche mission gets there.”

~~ Rich Olcott