Science In Real Life

SiRL: Quantum Weirdness pt 1 December 8, 2009

Submitted for your approval and your consideration: a quantum world. A world where Planck’s constant looms larger than life, where there are decent odds on quantum anomalies arising on your way to the corner store to pick up a gallon of milk. Where 70 years ago you might have found Einstein being chased by spooky action at a distance. You are traveling through a dimension not only of position and velocity but of probability. You have entered … The Quantum Zone.

Of course we don’t actually live in the quantum zone. We do not see the truly strange effects of quantum mechanics around us on a daily basis, even though the theory, when it was first formulated in the 1920s, suggested an application to all matter, all energy, all objects. It took decades for physicists to begin to understand this discrepancy. Research continues to this day into the precise processes by which the quantum weirdness goes away as we bridge the gap between microscale and macroscale mechanics.

But, if we did live in the quantum zone, your wavelength would be interfering with everything around you. Let’s talk about position in quantum mechanics.

( Image Source )

This right here is a wavepacket. It represents a photon, or an electron, or any other subatomic particle. It looks this way because, as quantum mechanics tells us, everything is governed by probability. What we have here is a graph of the particle’s wavefunction, which is related to the probability of finding it in one place or another. So, where is the particle? Who wants to take a guess? Let’s ask Professor Carlin.

What my esteemed colleague missed is that the particle isn’t really anywhere, at least not yet. Here’s the weirdness: everything, including us and this planet and your dear aunt Martha, exists as a matter wave. Carlin was right about one thing, though – it could be anywhere. What this graph isn’t showing us is that a real particle has very very small fluctuations out to the ends of the Universe. That particle could end up here, or in your hair, or in the Andromeda Galaxy; it does not possess a definite position … until! Until it interacts with something, colliding with another particle. That collapses the wavefunction to a single peak, a single position. And there we have the restoration of normalcy. Objects on our scale are trillions and trillions of particles all interacting with each other. They are constantly pushing on each other every which way, like members of Congress. And much like that venerated political body, all those pushes usually average out to nothing.

Another way we can see this, and with less recourse to cheap shots at the government, is by actually calculating the wavelength for something normal sized. Here’s the formula.

The Greek letter lambda means wavelength, m is mass, v is velocity and h is a constant called Planck’s constant. Planck’s constant is already a small number, so you can see that the wavelength for anything of appreciable mass is going to be smaller than the object itself. For an average human walking across a room, the wavelength is about 7×10^-36 meters. That’s smaller than a really really small thing. That means the wavepacket is extremely localized, and all is as it was before.

A related bit of weirdness is embodied by something usually known as the Heisenberg Uncertainty Principle. The most common one, and the one we’re going to discuss, is properly referred to as the position-momentum uncertainty principle. It says that the indeterminacy in a particle’s position is inversely proportional to the indeterminacy in its momentum — one goes up, the other goes down — and that their product is always greater than a minimum value. Heisenberg, the old jokes go, was driving down the road when he was pulled over by a police officer. “Do you have any idea how fast you were going?” says the officer. “No,” replies Heisenberg, “but I know exactly where I was!”

In short, because a change in momentum creates a change in position and vice versa, the two are eternally linked in an indissoluble bond of give and take. One way this manifests is in observing particles. Naively, we can imagine using a flashlight to look for a particle. Light rays bounce off the particle and into our eyes, telling us where it is. But light rays, also known as photons, carry energy, and the particle goes careening off in a new direction. By the time we see the result, the particle is already somewhere else. Why isn’t this a defense against speeding tickets? “But officer, your radar pushed my car over the limit!” No dice – for anything on our scale, the energy of light is far too small to have a significant effect. So yes, you are constantly being buffeted this way and that by every Peter Photon and Emily Electron that happens to come your way, but they are having about as much effect on you as the Lilliputians had on the awakened Gulliver.

Okay, that does it for tonight. Tune in next time for even more weirdness!

SiRL: Baseball December 3, 2009

Greetings, sports fans, and welcome to a very special Science In Real Life about the physics of lobbing the leather. I’d especially like to welcome those of you who are reading this on or from This Purist Bleeds Pinstripes, and thank the Purist herself, who had the balls to allow me to write a guest post for her esteemed virtual publication. Hopefully, for you who are getting an exhibition pass to the way we do things over at SiRL, you will enjoy yourself enough to sign up for a season ticket. Now that I’ve made my pitch, get the wax dug out of your ears, and let’s play some hardball.

The physics of baseball as a whole is of course far too extensive to cover in one essay. Fortunately most of the interesting stuff is concentrated in the mechanics of pitching, which is an aerodynamic spectacle unto itself. It also has the advantage of being extraordinary science hidden behind an ordinary phenomenon – we’ve all watched baseball, and we’ve all thrown spherical objects ourselves. What’s to get, anyway? “It just flies through the air!” you might insist. This is akin to insisting that the economy may be accurately described as “It’s just moving money around!” Sure, you can do it, but you miss all the fun that way.

The fluid dynamics of a baseball pitch, in their full glory, are as complicated as those of a hurricane or an episode of Jerry Springer. But we can dissect some of the basic concepts anyway. First we need the idea of a boundary layer. If you’ve ever had to clean the blades of a rotating fan, you might have wondered why it is that they need cleaning in the first place – shouldn’t the dust get blown away? Would that it were so, but friction’s domain extends even to air. Friction ensures that a thin layer of air hugs the blades as they whir; any dust particles short enough to ride inside that layer get a free pass. The same holds for a baseball (or indeed any object moving through air).

Enter the Magnus Effect. If it sounds imposing and impressive, that’s only because it is. Imagine watching a thrown pitch from overhead. Suppose that as it travels to your right, it rotates counterclockwise. The air hits it head-on (apply directly to the baseball) and splits. The air that follows the ball’s rotation stays a coherent boundary layer slightly longer than the air that goes agains it. Check out this handy diagram:

( Image Credit )

We can see that one side of the ball there is more turbulent flow, which is scientific jargon for “a giant mess”. In turbulent flow the air molecules push every which way. Since that push is heavier on one side than the other, there is a net force “into” the direction of the ball’s existing rotation. In full rigorous glory, the Magnus effect is stated as: A rotating body with velocity V relative to the fluid experiences a net force perpendicular to the direction of both the velocity and the axis of rotation.

From there it’s really just a hop, skip, and a jump to the cornucopia of curves charging into the catchers’ claws. By changing which way the ball is gripped, and the angle through which the arm rotates during the throw, a pitcher can change the axis of rotation. In addition, as with many things in life, controlling the speed of rotation is all in the wrists. Pure backspin on a ball results in an upward force, stabilizing the throw into a speedy straight trajectory – a good old fashioned fastball. A rising fastball does not actually rise, of course. That would require a backspin three times as rapid as what major league pitchers can currently achieve. Instead, it plays off our intuition about falling objects. We are so accustomed to seeing objects fall at 9.81 m/s² that a slowly falling fastball appears to rise.

The rest of the classic tools in a pitcher’s arsenal involve some kind of lateral rotation, and hence a lateral deflection relative to the trajectory of a nonspinning ball. In other words: yes, curveballs really do curve. So do sliders, screwballs, slurves, and any of the innumerable variations on that theme. Here is a handy guide to what rotation the hitter will see for the four most common pitches from a right-handed pitcher:

Every pitch has something like this, with two notable exceptions. Those exceptions look like this:

( Image Credit: Science In Real Life )

The gyroball (recently invented in Japan) looks like a fastball, quacks like a fastball, but spins like a duck. I mean, a bullet. To batters expecting the limited drop of a fastball, this can come as quite a surprise. You will notice that the knuckleball there has no arrows – it is thrown without any deliberate spin. A pitcher throwing a knuckleball puts his or her fate into the hands of Papa Physics. Stray fluctuations in wind speed, air pressure, and density can have this pitch wobbling every which way over, or not over, the plate. Without extensive practice, a knuckleball might, well, strike out.

SiRL: Eyes December 1, 2009

There is an old thought experiment that goes like this: Get an infinite number of monkeys and give them each a typewriter (these days it’d be a laptop), and monitor all of their output. With an infinite number of monkeys banging on an infinite number of typewriters, eventually one of them will produce the complete and unabridged works of William Shakespeare. When I think about what biological evolution has done on this planet, I cannot help but be reminded of the monkey typewriter scenario. Instead of an infinite number of random text generators, we have a finite (but still very large) number of organisms, with some number of random genetic mutations occuring every generation. Given that system in some specific environment, it would be surprising if optimal arrangements did not arise. And so it is, in our Sun-drenched environment, that that marvelous organ known as the eye has evolved and re-evolved and refined itself over and over again in the 3.7 billion years of life on Earth.

Our eyes, you may be surprised to learn, are simple. Each one has but a single chamber for sensing light – how bourgeois. The arthropods (arachnids, insects, and crustaceans), on the other hand, have compound eyes with thousands of photosensitive facets. What these two different types of eyes are, are two different solutions to a single problem, like Macs and PCs. Before we get to what that problem is, we have to start by dissecting the basic unit of organic vision: the biochemical photoreceptor. And for that we need a weapon that is to physics what firearms were to medieval warfare: quantum mechanics.

If you want an organ like your brain, which functions by the transmission of electrical voltages, to respond to light, you need a way to convert an optical signal (light) into an electrical signal. The way our eyes do it is by molecules called opsins that react in a very special way with photons. An opsin is a very complex molecule, with lots of bonds of different shapes and sizes connecting its atoms. Those bonds consist of shared electrons. When a photon comes through and knocks one of those electrons loose, the bond structure is disrupted. Opsins happened to be shaped just right so that when visible light hits it, it is disrupted in just such a way as to not break clean in two but twist around on itself into an alternate form. Think of it like what happens to Bruce Wayne when he sees the Bat Signal – he’s the same person, but in a different form, one that operates in a different way.

What happens next is a long sequence of biochemical transformations. The upshot is this: that one changed opsin molecule alters a whole bunch of proteins which then go around the photoreceptor cell locking all the doors and closing all the windows. The cell is now denied a flow of positive ions which it was previously enjoying, and so it becomes negatively charged. That, then, is the beginning of the signal which is transmitted to the brain.

So now we have this structure that can sense light. But if you’re an evolving organism on an up-and-coming planet like Earth, that’s not good enough – you need an image of the world around you. Here is where we come back to simple vs. compound eyes. Starting from a single area of photoreceptors on an animal’s skin, there are two ways to create focus (that marvelous phenomenon we all take for granted in photographs). You can surround your photoreceptors with refracting materials to bend the light, or you can add thousands more photoreceptors, each one aimed in a different direction. Either way allows differentiation of the light depending on the location and size of the source. The former is our simple eye, the latter are compound eyes.

The way this focusing happens is an elegant illustration of the principles of optics. For a compound eye, the directionality of the facets means that the light rays from the edges of an object-shaped object in view only activate photoreceptors on the edges of an object-shaped region on the compound eye. It is as though a smaller version of the object has been projected onto the lens. Next up, on Simple Eye For the Straight Guy, all the light enters through one aperture, so we need to be a bit more clever. Light rays from all the different parts of the object will all be coming from slightly different angles. The cornea, lens, and vitreous humor bend the light so that we once again have a projection of the object. This time it’s upside down, but your brain adroitly corrects for that.

I suppose now you’ll want color vision too. Very well. This is done by having more than one type of photoreceptor. Be you insect or simian, you have either rods or cones. Rods respond purely to light intensity; they are your night vision. Cones come in three flavors loosely corresponding to red, green and blue colors. If an orange flies past your face, your rods will tell you that something very bright is very close, your red and green cones will stand to attention in roughly a 2:1 ratio, and your brain will interpolate all of this to generate an image of citrus in motion. If the orange happens to fly at your face, you will have all of this information plus the added benefit of knowing exactly where the orange is at the moment of impact. Isn’t science great?

SiRL: Food November 26, 2009

Today is, of course, the American holiday of Thanksgiving, where friends and families all across the nation gather to celebrate that most favored pastime of this great land: eating absurd quantities of food. And it is in that spirit that I devote this Science In Real Life essay to the chemical process by which our body extracts and uses energy from the foods we eat. From poultry to pumpkin pie, from giblets to gravy, all of the food we eat stores chemical energy in the form of carbohydrates or fatty acids, and all multicellular animals use the same biochemical processes to function off of those fuels.

First, though, we need to understand how it is that a molecule can carry energy. Consider for a moment the Empire State Building. In this corner, weighing in at about 370,000 short tons (that is, tons of the 2000 lbs each variety), we have an edifice with most of its mass lifted up from the surface of the Earth. But gravity attracts everything – how is it not a heap of rubble? Because the structural arrangement is elegantly designed to resist exactly that process. There is energy contained in that building in a form called Gravitational Potential Energy; it’s Potential because the energy has the potential to be released if the building falls down. A quick back of the envelope calculation suggests that at current levels of American energy usage, the gravitational potential energy in the ESB is enough to fully power 20 households for a year. If the current energy crisis gets particularly unbearable and some clever chap designs a way to extract energy from falling buildings, we could blow up skyscrapers to heat our homes.

In this way do molecules contain potential energy – only this time it’s not gravitational, it’s electromagnetic. Molecules are made of atoms are made of charged particles, and a negatively charged electron in a chemical bond in a molecular arrangement contains some level of energy by being restrained “above” its positive counterparts. Left entirely to their own devices, molecules would all “fall down” into the lowest energy arrangements. But we are fortunate enough to have a source of energy which is as abundant as the sun. Sunlight becomes sugar, thanks to photosynthesis, and we ingest the sugar. You see, unlike today’s tech companies, Momma Nature has actually implemented a design credo based on interchangeable components. Glucose (C6H12O6) is the currency of choice for 99% of lifeforms on this planet; the rest accept VISA and Mastercard.

So you’ve wolfed down some glucose (or maybe some more complex sugars, or even a carbohydrate polymer or two – your body will have broken it down to glucose within minutes). Then what? Enter glycolysis, an ancient and venerated metabolic pathway. Since before time was counted, since before the sun rose over anything with limbs, even before prime time television (gasp!) there was glycolysis. Now, the actual biochemical process that is glycolysis is more complicated than I can explain here. But the upshot is exactly what I described above – the tight chemical bonds of glucose are broken, and the energy from that is used to form new molecules. In this case, the relevant products are substances called Pyruvate (C3H4O3) and a molecule called ADP, for Adenosine DiPhosphate. If glucose is the incoming mail for your body, ADP (and its relatives A-Tri-P and A-Mono-P) are the internal memorandums. They are used to transfer energy in and around the different parts of every single one of your cells.

But we still have to deal with this pyruvate business. Here is where your body really kicks it into high gear with an engine called the Krebs Cycle. This is … complicated. Here, scope this out:

( Image credit: Wikimedia commons )

Did your eyes just pop out of your head? Mine did. Doctors and biologists know this cycle like the proverbial back of the proverbial hand. I am neither of those things, but the nice thing about being a physicist is I get to cheat – the twin principles of conservation of energy and increasing entropy are always at work, throwing badly behaved misconceptions out of our heads like bouncers at an exclusive nightclub. We know, therefore, that energy comes in with the pyruvate and leaves with everything else. We also know that because the energy is going from concentrated (one molecule) to dispersed (many molecules) there are transferences of energy taking place. Where energy disperses, entropy increases. And where entropy increases, heat increases. Congratulations, you now have one warm-blooded mammalian body, ready for use. This cycle, ladies and gentlemen, is where some of your body heat comes from.

The rest of it merely happens further downstream. Those sunburst molecules of ATP and GTP (energy carriers) float away from where the Krebs cycle happens (that’d be your mitochondria) and into the rest of the cell, where they are picked up like dollar bills by so many hopeful entrepreneurs, and used to conduct the normal operations of your cell, like repairing structures, moving muscles around, reproducing, et cetera. Those processes also generate “waste” heat, which goes into warming you up. At a rough estimate, 60% of the energy you ingest goes into keeping you warm, and only 40% to the energy available for voluntary actions like moving, thinking, and writing science essays. Now if you’ll excuse me, I have to go consume large amounts of high-energy chemical bonds. Happy Thanksgiving!

SiRL: A Glass Of Water November 24, 2009

It is time to take Science In Real Life back to its roots. What I am going to do with this essay, what I have been aiming at all along, is to show you a glimpse of the Universe through my eyes. Through the eyes of someone who has spent years studying that which cannot be seen, heard, or smelled directly, but which must be studied indirectly, and studied for years if proper comprehension is to be obtained. Years of effort have given me a new layer of additional information accessible to me merely on examination of an otherwise familiar object. And that, dear readers, is what I am going to share with you today. Physicist Neil deGrasse Tyson once said, “We are all connected. To each other, biologically. To the Earth, chemically. To the rest of the Universe, atomically.” I tell you now that each and every one of those connections surrounds us in every moment. I tell you now that you can see all of that and so much more in a single ordinary glass of water. Come with me, and let’s explore.

Biologically

Go ahead and pour yourself a glass of water. Set it down on the table. Stare at it. You might think that it’s just water, but you might just as well convince yourself that a school building contains only students. Yes, the students comprise most of the volume, but it is the trace elements that really make the magic happen. From a biological perspective, the water in that glass is teeming with life. Exactly what life is in it will vary from region to region, but you can be assured that bacteria of all shapes and sizes are happily doing the Bavarian backstroke in your water. Most protozoa are rougly 100 times smaller than the human eye is capable of seeing (there are visible ones, but they are quite rare by comparison). Micro-organisms by the millions are inside just eight ounces of transparent fluid. If you were to drop a few pinches of sugar in and put it in the sunlight, you could create an ecosystem that would sustain itself for thousands of years.

Speaking of sugar, all kinds of organic molecules are in our drinking water. Where do they come from? Us, of course. We are dumping food waste by the metric shit-ton – pardon the expletive, but I mean it literally. Into our water supply via our waste systems goes a lot of wasted food, both of the digested and undigested variety. In addition to whatever you rinse down the drain or wash off your plates, some portion of the food you eat simply passes through you unscathed and ends up in, for example, Puget Sound, where researchers have measured seasonal variations in runoff sufficiently fine-tuned to, if one were feeling particularly Holmesian, deduce things about the American diet. Not only food, but prescription drugs as well, although so far not in concentrations to give you anything lasting more than four hours, if you know what I mean.

Chemically

The chemistry of water is amazingly complex for such a simple molecule. But before we get to that, there are more contaminants to deal with. Minerals like calcium, magnesium, and sodium are largely responsible for most collections of water being as electrically conductive as they are. Pure H20 all by itself is not a great conductor, but scatter a few ions through it and you suddenly don’t want to be in the pool when the thunderstorm hits. Which brings us to chlorine and flourine, two substances artifically added to keep the dangerous stuff from growing in the water. Behind all the biology, your glass of water is a chemical bonanza!

And then there’s the chemistry of water itself. H20 has some remarkable properties. For such a tiny molecule, it packs a punch of polarization. Known in some circles as the universal solvent, the electrical properties of a water molecule by itself translate en masse to a substance that is as adept at pulling things apart as your three year old nephew. Water can also act as either an acid or a base (chemists call it amphoteric), making it instrumental in many of the chemical reactions so very common on planet Earth. We humans, and indeed almost all life forms on this planet, are mostly water – for a planet whose surface is also mostly water, this indeed connects us inextricably and irreversibly with our home planet. It is remarkable just how thoroughly connected everything is to everything else, by interchanging chemicals, through one simple truth: water flows. Inside your water glass are molecules, H20 and otherwise, that have been all around the world and back again.

Atomically

Here is where I could go on for far too long about a myriad of properties of this incredible liquid: its relatively high heat capacity enabling ecological mediation, its hydrogen bonding enabling so many different molecular arrangements, its astounding surface tension – here, look at the surface of the water in your glass. You will see the water rise ever so slightly when it meets the glass, as though making a bid for freedom. That is surface tension at work. The water clings to the glass and simply does not let go. Insects have evolved to take advantage of this; by being sufficiently light they are able to walk across as easily as we cross a room. Capillary action is a consequence of this. The stick-to-it-iveness of water enables 200 meter tall redwoods to siphon it up thin cellulose tubes to the highest leaves and branches.

But this is not the aspect of water that really connects us to the Universe. It is that the atoms of water, for all their extraordinary properties, are made of three very ordinary things: electrons, protons, and neutrons. They are governed by the same laws of gravity and electromagnetism and quantum mechanics that hold sway across the uncounted reaches of all of space and all of time. Everything that has ever been has helped to shape the Universe that you occupy, and you continue to shape the Universe as you live. An entire cosmos has led up to your glass of water, and an entire cosmos leads away from it.

SiRL: Experiments You Can Do At Home 2 November 19, 2009

Welcome, welcome, one and all. Gather round, take a seat, preferably in your own living room. This is part two of *coughcoughmumble* of the Experiments You Can Do At Home series here on Science In Real Life. Last time the experiments focused on electromagnetism; it can be found here in case you missed it. Today we’re under pressure – air pressure. So grab your gear, guys and gals, and let’s get sciencing!

Put That In Your Pipe and Smoke It

Okay, for this experiment you will need just three things: a campfire burner (butane will work nicely), a PVC pipe about 5 to 10 centimeters in diameter (we use the metric system here at SiRL, none of that imperial nonsense for us) and at least a meter long, and your wits. Your mission, should you choose to accept it, is to find some way to make sound with these two items, other than banging them into each other like a confused, angry monkey. Hint: turn the burner on. Okay, lemme know when you’ve figured it out.

I’ll wait.

… no? Okay. Here’s what you do. With the burner a-burnin’, hold the pipe in a vertical fashion so that its lower end is hovering just above the flame. Fiddle with it until you get the position just right. (And the award for Best That’s What She Said Moment in a Science Essay goes to …) If you have it vertical, and just the right distance above the flame, the tube will begin to sound off with a deep, resonant tone. Words don’t do it justice, honestly, but having heard it myself I can tell you that it is a much louder sound than you would expect these two objects to be able to produce. If you only try one experiment this year, make it this one.

Alright, enough cheese. Let’s suss out why whatever is happening here is happening. Flames, such as the one coming out of your burner there, are hot. I trust this is news to no one. That heat radiates, conducts, and convects itself out into the surrounding air. The air heated by the flame then rises upwards, drawing cooler air in from below. Lather, rinse, repeat. When there’s no pipe present, that’s the end of the story. But now introduce the pipe. I cannot stress how important geometry is to physics. The key concept here is that the shape of the pipe constrains the waves of heat coming off the flame. With air at one end of the pipe going like gangbusters, and traveling in the form of heat pulses up the length of the tube, there is what we call a fundamental mode (not to be confused with the natural state of being of Fred Phelps). It is the lowest energy oscillation possible given the source and geometry.

That fundamental mode, in this case, happens to occur at an audible frequency suitable for the likes of Mufasa, Darth Vader, or even James Earl Jones. Speaking of cool cats …

Schrödinger’s Cat

So for this one you will need an ordinary domestic shorthair feline, a box large enough to hold same, a small amount of radioactive substance (Americium from a household smoke detector will do), a geiger counter, and a switch controlling the release of — what? Really? Oh, fine. Ladies and gentlemen, the ASPCA has just informed me that I am not allowed to actually do this experiment. Fortunately I have a backup plan.

Stop the Presses

Get yourself a copy of one of those old fashioned print newspapers (before they die out for good), a thin plastic ruler (of the 12 inches variety, not Prince Charles), and meet me at the kitchen table (aw, here it goes). Take just one sheet and fold it in quarters. Place the ruler with half its length protruding from the table’s edge and the folded newsprint on top of the remaining half. Stand to one side and make sure no one you terribly care about is standing on that side of the table, because now you’re going to whack the protruding ruler as hard as you can. Wow, look at it go! You must have gotten a good 5 meters on that. Judges? 9.9, 9.8, and … 8.5? Oh well, there’s always the bobsled competition.

Let’s try this again, only this time you unfold the paper sheet to its full area and use it to cover the table-bound half of the ruler. Flatten it out as much as possible. This time you can get the whole family to gather round, because when you whack the ruler it is going to move about as much as the Californian legislation on gay marriage. What happened? Air pressure happened! The mass of the newspaper is tiny, so the only real difference between exhibit A and exhibit B is the surface area of the paper. By conscripting more area, you also conscript a lot more air, pressing it into the service of holding down the paper, which in turn holds down the ruler, all in the house that Jack built. Not only that, but you have vastly increased the paper-table contact area, which has vastly increased the friction resisting the paper’s motion. That, unfortunately, is a topic for another essay.

Now go forth, my readers, and do science to things!

SiRL: Symmetry November 17, 2009

A very important notion in physics is symmetry, although perhaps not in the form we are most accustomed to seeing around us. Biology as well possesses symmetry, and it is here that we are faced with some of the symmetries that we already countenance from day to day. Chemistry, in the form of molecular structure, also embodies fundamental notions of symmetry that help construct the world around us. Doubtless the entire natural world relies at its very core on various forms of symmetry.

Even though we hear the word frequently, most people don’t know that symmetry in physics reaches deep into the structure of the Universe. First, though, let’s start with an ordinary square, with some Cartesian axes included:

(Image Credit: SiRL)

Gee, this is one symmetrical figure – it has matching pieces on either side of each axis. However, those are not the only ones, since we can also use a diagonal line through the center. It so happens that squares have what we call bilateral symmetry. Just like your face, if we imagine flipping it across that line, it would come out the same. Kids these days (all the cool ones doing science, anyway) call that a reflection, which is a particular example of a very general thing called a transformation. Like it or not, anything you can do to an object, from lifting it up to causing a nuclear explosion, is a transformation. Move that square to the left and you have transformed its position by whatever distance you used. Notice that its essential properties, the things that make it a blue square, are unchanged.

Once you accept that any system can be characterized by a handful of parameters and equations that relate them, it is intuitive to see that any transformation which leaves those equations unchanged must correspond to some constant quantity of the system. Physicist and mathematician Emmy Noether was, in 1915, the first to realize this brilliantly elegant result that has since transformed all of physics. Quite simply, all of the basic conservation laws in physics (like energy and angular momentum) have with this law a simple operational manifestation. Rounding out this idea’s impressive list of accomplishments is a hefty contribution to the development of modern particle physics. Seeing conservation laws in particle interactions led to symmetries led to new predictions, et cetera.

Turning up the complexity a notch, the idea of broken symmetry has found use on the frontiers of physics. Unlike the four forces we have today, early in the Universe (it is suspected) there was just one. Very dramatic expansion and cooling broke that symmetry. When, in particular, the electromagnetic force separated, particles acquired mass. Xanadu the Universe might no longer be, but thanks to the Higgs boson we can form life as we know it. Yes, that Higgs boson. Zounds! You didn’t know, I’ll bet, that all of that stress and agita over the LHC was to find out what kind of broken universe we live in. Xanax might help.

Well, of course physics doesn’t have a monopoly on symmetry. Vases and visages both have it, but first the biology. Ubiquitous throughout the plant and animal kingdoms on Earth, various forms of symmetry dominate the landscape. Truly rare is the ambulatory creature that does not exhibit bilateral symmetry of its entire body. Some of your favorite fruits have spherical symmetry, although here I am comparing apples to oranges. Radial symmetry attracts adherents among a lot of the flora, and bilateral symmetry brands their branches. Questions then arise about why it is so common.

Postulating reasons to explain why evolution zigged instead of zagged is a risky proposition, but we can see there are several advantages that follow from symmetry. On the fauna side, the balance of bilateralization allows for faster locomotion, as well as the centralization of a nervous system. Next, for plants, having such a simple blueprint as radial symmetry is very efficient from a resource management perspective. Moving nutrients through the organism becomes easier, and even the very genetic construction of the plant is simplified. Ludicrously long strings of DNA would be required to build an asymmetric ficus; the ficus with the short genome is less at risk from transcription errors and other harmful mutations (this goes for the animals too).

Kindly zoom in further, and we will see that (a)symmetry is at work at the biochemical level as well. Just like people, organic molecules can be right- or left-handed, and while the lab can synthesize both it seems that life on Earth has chosen one form or the other for each of the common proteins and amino acids. I don’t know if chivalry is dead, but chirality is alive and kicking.

Humans have a massive predilection for symmetry, motivated no doubt by the symmetry of the human form. Guess if you have to, but try to think of the last asymmetric object you saw – I bet you can’t clearly picture it. From Kiev to Carolina, the devices and objects with which we surround ourselves are overwhelmingly symmetrical. Either it’s biology or culture or some mix of the two, but something about symmetry activates very old pathways in our brains that tell us that is how things are supposed to be.

Dubious you would be if I told you this essay covered everything there is to know about symmetry, and rightly so. Come what may, however, you now have a basic idea of how thoroughly the concept pervades our lives. Balance is everywhere. And now it’s here too.

SiRL: Signal to Noise Ratio November 12, 2009

Around us all we see without cessation
A great vast flowing sea of information
Causing truancy of our cogitation;
With such a great morass of obfuscation
Impingent on our senses night and day
How ever shall we learn to find our way?
We must train to keep the bullshit at bay
And distinguish the horses from the hay;

A trick often used by us science folks
To tell the legit ideas from the jokes –
The signal to noise ratio, you mokes,
Is always low when looking at a hoax;
So first the term of “noise” we shall inspect:
If the cause of something you suspect
Is absent from the system you select,
The noise is the effect you still detect;

By contrast the signal is the accord
Between what you believe and you record;
If it’s correct you may get an award,
If not, back to the drawing board;
In particular when a claim is made
Better than chance it must have gone and stayed,
For if into the noise it has decayed
Your statement is likely false, I’m afraid;

If your friend says the rock he holds upright
Keeps him free and clear throughout the long night
Of any tiger, tiger burning bright
It’s useless if you’re on the Isle of Wight;
If the salesman says your cold he can cure
You drink his drink because it looks “so pure!”
But it still takes a week to run its tour,
You have been had by that entrepreneur;

This is why we scientists use controls,
So when our data’s doing barrel rolls
We can compare against the exit polls
To see if our theory will reach its goals;
So the next time somebody tries to sell you
On claims whose truth is of dubious value
The signal to noise ratio will tell you
Whether you should buy in or just run them through.

SiRL: Light November 10, 2009

How are you reading this essay? Since the Science In Real Life audiobook hasn’t hit stores yet, you must be absorbing the information through your eyes. That means you’re using light, until such time as the radiation from the hole in the ozone layer gives us all psychic powers. Way back in the Electricity and Magnetism essay, I explained how a light wave is a combined oscillation of electric and magnetic fields. I’m going to take that as a jumping point and start going into some of the basic properties of light as they pertain to how we as organic beings interact with it.

The first thing to note is that the light we can see with our eyes is just a very small slice of the electromagnetic radiation cake. Imagine the bakery screws up your order and sends you an infinitely long line of cake. Off to your left, the low-energy cake represents radio waves, microwaves, and infrared radiation. Right in front of you is a rainbow of visible cake. Then, as you head right, you get ultraviolet, x-rays, and gamma ray cake. Tasty!

Sometimes you will see the electromagnetic spectrum labeled with the various frequencies, other times with the corresponding wavelengths. We can do this because frequency and wavelength are related. Check out this graph here.

( Image credit )

Since a wave is a repeating cycle, we define the wavelength (frequently denoted by the Greek letter λ) as the physical length of one cycle. The number of cycles that pass per unit of time is the frequency, f. How can we relate the two? Imagine instead of abstract cycles, we have bicycles. You’re watching the Tour de France and all of the bikes are going past you single file, in a wheel-to-wheel line. You know that all of the bicycles are 2 meters in length and you see 6 of them go by every second. How fast are they going? In one second, six two-meter bikes go by, for a total distance of 12 meters. Two meters times (6 bikes/1 second) gives 12 meters per second. Quantitatively, frequency and wavelength are related by the speed of the wave: fλ = v.

Much is made of the importance of the speed of light. It is often said that nothing can go faster than the speed of light. Taken at face value, this statement is demonstrably false, since the speed of light is greatly reduced inside matter, and can even be reduced to zero. We have to add the following qualifications: no inertial object (that is, something made of matter like you are) can accelerate to the speed of light in a vacuum or beyond. That “in a vacuum” is crucial – only when light is traveling per nihilo does it attain that magnificent maximum speed.

(Advanced note: That other bit about acceleration is in there because it is acceleration’s peculiar bending of spacetime that runs up against the conservation of energy. If you can figure out a way to propel something at faster than light speed without accelerating it, you will be able to buy and sell Bill Gates six times before breakfast.)

So why is there a maximum speed, and why is it associated with light? That maximum speed is what it is for reasons having nothing to do with the character and behavior of light rays – it is a fundamental limit on the speed of any kind information through space and time (except rumors). Things with rest mass, like your little sister, are restricted to using most of their energy-as-mass to maintain corporeality. A light ray, on the other hand, can blow its whole load of energy-as-energy on extra unleaded liquid Schwartz to blast across the cosmos at 300,000 km per second.

Lastly, I want to briefly address the fundamental nature of light from a quantum mechanics perspective, as specifically pertains to the quantum buzzphrase “wave/particle duality”. Physicists debated for centuries the question “Is light a wave or a particle?” So you can imagine the collective surprise when the answer turned out to be Yes. Depending on what experiment you perform, light rays can be shown to have, undeniably, irrevocably, and incontrovertibly, properties belonging to both wave and particle definitions. “Okay, fine,” you say, “so what is it really?” The answer is it is something else entirely, some entity that can exhibit both behaviors, much like the man who is both Bruce Wayne and Batman. “Okay fine,” you say, “but what IS that, really?” Well, we don’t know. So far, scientists have been content to call it ‘light’, but the search for a more lucid understanding continues.

SiRL: Experiments You Can Do At Home November 5, 2009

Home, they say, is where the heart is. So what better place to really get in touch with science? Yes, the cutting edge of science is full of expensive machinery and delicate arrangements, but there are about a gajillion (± a zillion) simple experiments you can do right in your own home to illustrate scientific principles both simple and complex. This essay marks the beginning of an occasionally appearing N-part series, where N is some large and as yet undetermined number.

Electricombly Charged

Let’s begin with your hair. Really, it does need a combing. Head on over to the bathroom and whip out your trusty plastic comb. Start a small stream of water running. Bring the comb near the water without touching it. The result should be a profound lack of change. The water is as unmoved from its downward trajectory as whatever football team it’s fashionable to insult this year. Now pass the comb through your hair – a dozen or so passes should be sufficient. This time when you approach the water, it bends towards the comb like it suddenly has a pressing appointment in your toilet bowl. The more you pull the comb through your keratinous knots, the more you are able to pull the water stream.

What’s going on? Electrostatic buildup. The friction between your hair (which actually looks fine, I promise) and the comb is violently ripping electrons away from the atoms atop your cranium, resulting in a buildup of electrons on the tooth-based hair manipulation system. That is one negatively charged comb which, being made of an excellent insulator such as plastic, gives the newly arriving electrons nowhere to go. All of this would be for naught, of course, if it weren’t for the other phenomenon at work here; and so we enter the nominal “discovery” phase of this experiment. Water, most of the time, is electrically neutral. So why the repulsion? Because of a little thing called polarization.

Each water molecule, thanks to having one electron-hungry oxygen atom and two less electron-hungy hydrogen atoms, has a slight electrical imbalance. With the water flowing sans comb, the molecules are oriented every which way, slipping and sliding this way and that on their way down. But along comes the negative charge, and now they are lined up like soldiers on parade. The molecules turn so that all the positive sides are towards the comb. Against the protests of the negative sides, the positive ends then rush as hard as they can towards the comb. Presto chango, one bent stream of water. In addition, it so happens that tap water contains minerals that conduct electricity very well. These also produce a polarization effect.

A Light Snack

Well, all of that water bending has certainly worked up an appetite. Let’s get something to eat. For this experiment, you’ll need a microwave oven, a ruler, a flat tray or plate, and a bag of marshmallows. Stand all the marshmallows on end so that they form a uniform layer on the plate one marshmallow high. Insert this arrangement into the microwave oven – being sure to first remove the rotating platform if there is one – and let it do its thing until you see several distinct melted spots in the marshmallow array. Take the plate out and get ready to do some science.

Carefully, without getting gooey gelatin on your ruler, measure the distances between each melted spot. You should observe that they are all approximately the same. Find a friend who is good at math or a calculator, and average the distances. This is our measurement. But before we use the measurement to calculate something I bet you didn’t know you could measure in your kitchen, let’s figure out why we have discrete gooey spots and not one mass of melted ‘mallow. Inside your microwave oven is a device called a magnetron, which apart from sounding like a Bond villain’s latest attempt to fry Seattle is how the device turns electricity into microwaves. How it does this is another essay altogether – for now just imagine a magical gnome pumping microwaves into the chamber like it’s his job. Microwaves, remember, are just ordinary light waves at a lower frequency than the light we can see.

So the microwaves pour into the chamber and start bouncing off the walls. Then they meet up with the microwaves that came in while they were playing rumpus room. What happens when two waves meet? Anyone? Anyone? Bueller? They interfere with each other. The parts where they oppose go to zero and the parts where they agree get amplified. Soon what you have is called a standing wave, as in the cooking chamber is packed and there is standing room only. That means that there are regions of high and low amplitude that don’t move relative to the chamber. The former are what produced the gooey spots.

Now, it so happens that the distance from one high amplitude spot to the next is what we call the wavelength. That’s what we measured before. We’re almost there; look on the back of the oven to find where the manufacturer listed the frequency of the microwaves, it will be a number followed by Hz. Multiplying wavelength by frequency means dividing distance by time, so using the measurement you took before you can calculate … yes, that’s right: the speed of light. All 300 million meters per second of it. Now quickly grab some graham crackers and chocolate and enjoy your smores of science.