Yard -> Yacht

What a consonant set of options to choose from today. I went with these two because we all know alliteration is the best literary device.

A yard is, by definition, exactly three feet. (That’s about a meter, more or less.) But “exactly three feet” is only helpful if you know how long a foot is, which historically wasn’t a given. So people would estimate a yard as the distance from their nose to their outstretched fingertips. (Of course, this meant different people had different “yards”, but generally they’d be close enough—unless you were buying from a giant. Then: Bonanza.) (Self-promotion time: If you’re really into units and measurements, I’ve scripted a number of videos about them.)

For me, one of the most interesting parts of all this is that, subjectively, stretching out an arm feels like pushing a hand away from our body—even though that’s not what happens. Our muscles can’t push on our bones; they can only pull on them. When you extend your arm, muscles in the back of your arm (your triceps) pull your forearm toward your elbow, swinging your hand away from your body as a result.

There’s a similar (for a very specific idea of “similar”) misconception that surrounds sails. People think they’re pushed by the wind (like bouncy castles), but that’s only true sometimes. If it were the only option, sailboats wouldn’t be able to go anywhere but downwind. To go upwind, though, sails act more like wings than anything else, propelling the ship below along more through lift than direct wind-on-sail impact. Sails are wings turned on their sides.

Skirting around the mechanics of lift for the second post in a row, this was just as true for the ships of the Spanish Armada as it is for today’s yachts.

At least, as long as those yachts have sails instead of motors. But motors are a story for another time, too.

Brendan’s Adventures in Python

It would be a lie to say I’ve never done much programming, and I don’t like lying.

I learned bits and pieces of HTML in high school to customize my profile page (RIP Sodahead), and I learned some more in college to create a finding aid for one of my library jobs. I also dragged my feet and struggled to learn the fairly basic Mathematica required for physics classes.

But my main programming experience came from research. I used MATLAB to analyze data and create figures like this beauty:

Fun fact about me: I love this figure so much that my master’s thesis is dedicated to it.

More seriously—and more relevantly for this post—I found backdoor ways of making MATLAB do animations and displaying something like a movie, which it was most certainly not built to do.

Long story short: There’s a thing moving through fluid. We watched it with four high-speed cameras, built the object in a computer, and matched the one we built with the one on the cameras.

But that only went so far, and then I graduated and set it aside. In the last few years, if I needed an animation, I used PowerPoint.

Then, about two or three years ago, inspired in part by creators like 3Blue1Brown and the frequency with which Matt Parker says “Python” (that list of links took far too long to compile), I tried downloading Python to see what I could do with it. That experience was frustrating and unproductive to say the least.

Nothing made any sense and I firmly didn’t understand what I was doing. I could get some of the most basic things to work, but nothing more advanced—certainly not enough to do anything interesting. I also made the mistake, understandable at the time, of trying to learn from the ground up. So I started by learning how to make lists and move numbers around, which was dull enough that it made all the frustrations even more frustrating. I think I got as far as changing filenames before everything constantly breaking became intolerable. I gave up, set it aside, and went back to PowerPoint.

But then, at the beginning of this month, Rhett Allain posted this video on Reddit. I’ve always looked up to Rhett’s articles in Wired, and seeing him use Python so effectively in that video was the kick I needed to try it again. The tab with that video remained open for a couple days while I tried and tried again and tried a third time and tried some more to install something that should be far easier than it is, but eventually everything was working as desired. The trick, I learned, is that when you see an error, just keep uninstalling the things that throw the error until there’s nothing left to uninstall. Then try again, rinse, and repeat. (Note: This does not constitute actual advice. Although it did, in a sense, work for me.)

I set about following Rhett’s guide and it, delightfully, worked. After that, I was off to the races. Everything was (mostly) beautiful and nothing (some things) hurt. I added another mass on a spring below his and learned how to make sliders to adjust the initial positions of both masses, then went back and made a bunch of other simulations and toys to expand my horizons as I went.

It’s been going well so far and I’m having a lot of fun, but now I have the problem where I have a lot of good projects on my computer and the only one looking at them is me. I wanted to change that and share what I’ve been working on. To that end, I’ve added an Educational Resources page to this site with links to all the projects that I’ve put onto Trinket. They’re all available to use by educators and anyone else seeking to develop some physical intuition.

I’ll keep updating that page as I make more, and I’m open to new ideas to add to my growing list. I hope people find them useful. They certainly are fun to make.

Bike -> Drums

When you learn to ride a bike, adults tell you it’s easier to stay upright the faster you’re moving. I suppose some kids take this as license to rocket downhill, but I was never one of those kids. I always heard it as one of those lies adults tell you. I’ve never liked going particularly fast, and I always balanced just fine.

What I didn’t know at the time is that bicycles can balance even without a rider—and generally the faster they go, the better they balance. Now, there are arguments about exactly why bikes balance, with factors including the conservation of angular momentum, which makes it hard to twist a rotating object (like the wheels); a sort of drag on the front wheel that turns it in the direction the bike tilts, keeping it under the frame; and the distribution of mass in the frame, which forces it to fall toward the front wheel rather than sideways, even when the frame tilts. As interesting as that argument is, it won’t get us to drums. For that, we need the bike to fall.

You realize how heavy bikes are when one falls on your leg, but you also realize how loud they can be. They sure can clang, especially if they land on pavement. That clang comes from vibrations in the metal frame that start as soon as they’re hit by something hard like a rock. The more rapidly the metal vibrates, the higher-pitch the resulting sound. But you can’t easily change how quickly something vibrates by hitting it a little differently, at least not if you abstract away from the real world (as physicists are wont to do). Everything around us has its own resonance frequency—its own natural rate of vibration where it’s easiest for the atoms and molecules in the structure to exchange energy back and forth. Something’s resonance frequency depends on a bunch of stuff, and the actual sound you hear when something’s hit depends on even more stuff. But let’s keep abstracting away from that mess to find a good rule of thumb: If you have a bunch of tubes of the same kind of metal, longer tubes will make lower pitches when struck. The bulk of the frame will have a lower-pitch clang than the adjustable tube that the seat sits atop.

This is also true for the air inside the tube. If you blow over the top of a tube, longer ones will make lower notes than shorter ones. Pipe organs make music this way, as do flame-fueled Rijke tubes.

The source of all these sounds is microscopic vibrations, whether in the air inside the tube or the tube itself. All sounds are produced this way, even without a tube in sight. Sounds come from vibrations. And the rule of thumb holds true more widely, too: More material generally makes lower pitches because it’s hard to get a lot of stuff moving (as long as you keep everything else the same). The less energy it takes to get something moving in the first place, the more of that energy can go into vibrations.

This is why we can hear the difference between kinds of drums—say, between snare and bass. The snare drum is tiny and makes a high-pitched sound; the bass drum is much larger and makes a correspondingly lower-pitch sound. Admittedly, the drum heads might sometimes be made of different material, and also a snare often has stuff at the bottom to shake the sound up a bit, but that’s really neither here nor there.

And that’s the thread of continuity between bicycles and drums.

As a side note, I’m going to kick off this blog by doing one post a day for the first week, then I’ll settle down into the weekly schedule.

What Is This?

Science is beautifully interwoven. The light we use to understand the Big Bang is the same kind of light we use to heat up leftovers. The telescopes we use to see distant galaxies focus light the same way an inflated balloon can focus sound. The low pitch of rumbling thunder sounds the way it does for the same reason upstairs neighbors tend to sound like grumbling brutes rather than dainty mice. And so on. The more deeply we investigate the inner workings of our material universe, the more interconnected its processes and its physics seem to be.

In this blog, I want to explore some of those interconnections. My plan is simple: Every week, I’m going to go to this Pictionary word generator, set “Number of Things” to 3, “Category” to either Medium or Hard, depending on how I’m feeling that week, and hit “Generate Pictionary Words.” I’ll pick two of the words that pop up and write a little arc of physical connections from one to the other. I’ll post a screenshot of the result from the website, too, just to keep myself honest.

The goal, I suppose, is to be somewhere between an educational read and a good, regular writing exercise. Hopefully it turns out to be both. I can’t promise perfect rigor; I’ll do my best to source claims and double-check my writing, but there’s always a chance I read something wrong in my haste or just write something wrong. I certainly won’t always use semicolons correctly. Why expect anything more from my physics? If someone reads the blog and points out an error, I’ll correct it in the next post—and if that error breaks the chain from one topic to the next, I’ll find another way to connect them. I’ll also thank them for reading, because that’s about the nicest thing a person can do when another humans writes something.

On that note, whether you’ve read this far or skimmed to the end of this introductory post, thank you for reading.