Blizzard -> Tank

Growing up, I thought adults who said “nor’easter” were bad at saying “northeaster”. I was wrong.

Just about all nor’easters—a sort of winter tropical storm, for those not from New England—count as blizzards. But a blizzard is more than a bad snowstorm. It’s a winter storm with high winds and enough snow in the air to keep visibility fairly low for at least three hours. Since light bounces off snowflakes, the more snow in the air, the closer something has to be for most its light to get to you without being bounced all over the place first. Whether that snow came from the clouds or it was picked up from the ground by wind doesn’t come into play in defining the storm.

Snow muffles sounds just as it bounces light, but for a different reason. The coordinated vibration of molecules that forms a sound jiggles water molecules in the snow around and becomes random vibrations (heat). (Also, winter storms tend to have funny temperature distributions that refract sound upwards and away from our ears.) During a blizzard, with howling winds and sound-absorbing snow everywhere, you can only hear really loud stuff from afar—loud stuff like thundersnow.

But sounds dissipate with distance even without snow. Some of the coordinated vibration of a sound wave always turns into heat as sound travels through the air. Higher frequencies are especially susceptible: They start with more rapid vibrations at the outset, so it’s easy for those to get out of sync and become random noise. Also, it takes more energy to sustain more rapid vibrations, so the sound runs out of energy sooner. This means treble dissipates too quickly to be heard from a great distance. The farther you are from something, as a result, the lower-pitch it tends to sound. (Side note: This is also why people who live upstairs from you always tend so sound like they’re stomping and grunting rather than squeaking.) (Second side note: This is tangentially related to something I talked about for the Museum of Science [24:17 in that video is the question and then my answer], where you can tell the angle of a lightning bolt from the sound of the thunder.)

What’s true for natural processes is also true for natural processes that humans have a hand in—there’s nothing to be gained in separating us from nature, after all. So if you’re far from an outdoor concert, you’ll hear more bass drums, low voices, and low guitar chords. And if you’re close to a tank when it fires out of the big barrel, you’ll hear a wide spectrum of noises. But if you’re a ways away, you’ll mainly hear a boom. Hopefully you’re far away in the right direction.

Friction -> Cashier

Last day of doing this daily! After today I’ll settle down to weekly like I planned.

Friction between pieces of sandpaper has an obvious source: Sandpaper is lumpy. But lumps and bumps, whether at centimeter or atomic scales, are the source of any friction between two surfaces that are rubbed together. When bumps of one encounter lumps of another, they catch. (Everything is also made of electric charges that fleetingly attract the charges of other surfaces. On really big scales, this sort of process helps make lightning. But that’s a story for another time.)

Overcoming friction means shoving atoms out of the way, jiggling nearby atoms in the process. So friction turns useful energy into useless energy—what physicists call entropy. Those two sentences say the same thing, by the way. One just focuses on atoms while the other is bigger-picture. But I think it’s easiest to understand friction if you switch zoom level mid-sentence: Friction turns kinetic energy (energy of large-scale movement) into heat (energy of atomic movement). The more heat you get, the less kinetic energy you keep—and kinetic energy is the energy we use to power things like engines.

Energy is constantly changing forms. That’s all it can do, dark energy aside. It can’t appear or disappear. But as we’ve already seen, some energy is useful and some isn’t. The second law of thermodynamics says that over time, we’ll run low on the former while accumulating the latter.

The universe, then, is like a cashier who only gives change in pennies. Sure, you might pay for something with exact change (you might find some process that turns 100% of useful energy into other useful energy), but honestly that’s pretty rare and never really happens if you have a complex bill. The rest of the time, you put in more energy (more money) than you need, and the change you get back is completely useless.

Admittedly, we should probably try to pay in exact change during a coin shortage. I’m sure there’s a metaphor for renewable energy in there somewhere.

Cutlass -> Fuel

My first thought was to go from fuel through fire to blacksmiths, but I’ve gone down that road already. Let’s flip it.

A cutlass is a sword, and swords have to be sharp. (It’s also a kind of car, which has to be sharp in a different way to cut through the air.) But we’ve been sharpening things far longer than we’ve had swords. Members of our genus have sharpened tools for millions of years. We’ve gotten good at it by this point. We’ve gotten so good at it that the Ancient Greek philosopher Democritus used a knife to reason his way to a fledgeling atomic theory.

Here’s what he said: When you cut into an apple, some of the apple ends up on either side of the knife. But the only way the knife can get between the two parts of the apple is if there was already space between them. So there must be bits of matter with empty space between them. QED—or whatever the Ancient Greek version of QED was. It’s not quite the argument we’d use today, but it’s neat, even when summarized as fleetingly as I just did.

Modern atomic theory came from the dual directions of physics—where atoms explained temperatures and sounds and a bunch else—and chemistry—where atoms explained reactions. Chemical reactions seemed to consume the input elements in certain ratios, and we now know it’s because a certain number of atoms of one element would always react with the same number of atoms of the other: Two oxygens and one carbon became carbon dioxide, say.

Fire, as we know from the other day, is a complex collection of chemical reactions involving oxygen. But fires need two other ingredients. They need heat and, of course, they need fuel.

Scuba Diving -> Electrical Outlet

I’m surprised “electrical outlet” was a “Hard” Pictionary result. That seems like a pretty easy thing to draw. Regardless, let’s get diving.

Scuba diving involves taking a tank of oxygen underwater, which is necessary because humans, tragically, are only fish in the most pedantic of senses. We need to breathe oxygenated air, and the oxygen we breathe comes from plants: We’d suffocate without them, while they’d be fine without us. They make oxygen using plentiful carbon dioxide and water. But where does that oxygen come from—the stuff in the carbon dioxide and water molecules? We’ve got a ways to go, so let’s make this answer quick: Mostly molten rocks, and also some dead stuff.

But that doesn’t satisfy me yet. Where do the actual oxygen atoms come from that have been kicking around our planet for billions of years? They don’t come from chemistry or geology. They come from physics. Stars bigger than the Sun make oxygen all the time out of carbon and hydrogen (and another hydrogen), although admittedly most of it then turns into nitrogen. Dying stars of all stripes make more lasting oxygen by smashing together carbon with helium. When really big stars die, they explode in a supernova, blasting oxygen and other elements out into the cosmos. (Sun-sized stars typically hold onto the heavier elements they make, although evidence is mounting that they often end up growing big after they die and exploding anyway.) We breathe—and are made from—the ashes of ancient stellar explosions.

Stars themselves are made of plasma, which is either a fourth state of matter or a super-hot gas, depending on whom you ask. If you ask someone who’s focused on molecular motion, plasmas and gases are the same thing: Substances whose molecules zing around so quickly that they don’t clump together. But if you ask someone focused on conductivity, they’ll say plasmas and gases are quite different. In a plasma, the molecules move so fast that electrons are knocked off of them, creating a sea of charge through which electricity can flow quite easily. Plasmas are conductors, while most gases are much too diffuse to conduct electricity.

Back down on Earth, of course, we don’t have to seek out a plasma to find something conductive. We have metals that we form into wires and plugs. Plug something in and electricity—electrons—flow down the conductive wire from the electrical outlet.

Fiancé -> Shelter

When I proposed to my now-wife, I didn’t have a ring. Finding the ring size of someone who doesn’t wear many rings seemed hard, getting and keeping one in secret seemed harder, and I didn’t see the point when really I just wanted to marry her. She said yes anyway. (I think she liked me.)

That made me her fiancé, but, in one of English’s few remaining vestiges of nouns with grammatical gender, it made her my fiancée. Most fiancés have fiancées with diamond rings, both because of some pretty impressive marketing and because diamonds are well suited for finger adornment. When cut right, diamond can exhibit total internal reflection, where (loosely speaking in a way that would make some people mad) an incoming ray of light bounces around multiple times inside the diamond before coming out. This property makes diamonds seem to glint and shine from all angles, which in turn makes them glimmer when they’re on something that moves around a lot—like a finger.

Some diamonds are synthetic and some form from asteroid impacts, but let’s ignore them so that I can say: Diamonds are forged deep within the planet, when buried carbon is squeezed by immense pressures from something like colliding (or newly forming!) tectonic plates. The incredible pressure shoves carbon atoms into their most rigid possible arrangement—so tightly and perfectly packed that it’s nearly impossible to move an atom out of the way. This makes diamonds incredibly hard to scratch. But it also makes them relatively rare, at least compared to normal rocks. So as cool as it would be to live in a diamond house, it’s just not happening.

Instead, we make homes out of much more common stuff. We use wood where there’s a lot of wood. We use stones, sand, and water (and other stuff) to make concrete. We use mud and clay to make bricks. We use sand again to make windows. All of them make for a pretty sturdy shelter. And, honestly, I’d rather have privacy than a diamond house, anyway.

Hot Tub -> Shampoo

Okay, so there’s the obvious route: Hot tubs are like bathtubs, where you’d usually use shampoo. But there’s not much science along that path. Let’s see if we can forge another one.

Hot tubs are so relaxing because heat loosens our muscles, which is a big-picture way of saying that blood vessels dilate when they’re warm—letting our bodies transport bad stuff out of muscles and good stuff into them. (That itself is a big-picture way of avoiding biology.) There’s probably some biochemistry that goes into dilating warm vessels (there definitely is), but there’s also some pretty straightforward physics. Something’s temperature is a measure of the internal kinetic energy of its atoms and molecules: The hotter the object, the more its molecules wiggle and jiggle. Cold things tend to be rigid because their molecules don’t have the energy they’d need to adjust their positions much. Warmer things loosen up, and they also tend to expand: their molecules can spread out now that they have the energy to push their surroundings out of the way. The same must be true for the walls of blood vessels.

This is fundamentally why we clean with hot water, too. It gives grimy molecules the energy they need to break free from whatever they’re affixed to. An awful lot of kinds of molecules dissolve in water, so anything loosened by the heat tends to be carried away by the water. Washing with soap and hot water is even better—at least as far as dirt is concerned. Soap molecules either bond with or otherwise break into bits of oil or dirt, and it’s easier of molecules to react and rearrange when they have a lot of energy.

Ridding any surface of oils and dirt is the central job of any soap. Soaps get specialized because we might not care very much if a soap is designed to mount an all-out attack on a plate (ceramic can handle it), but we’d probably care more about a soap that does such a good job cleaning our hair that it destroys the hair in the process. That’s why we use gentler stuff on our hair: Shampoo might not be quite as good at breaking bonds as dish soap, but the trade-off is worth it for something made to be gentle. We also want stuff in our hair that washes away easily, and shampoo is designed to be just that.

There. That was a more interesting route, huh?