Alligator Clip

An alligator clip taped to a steel rod.
Fierce fellow!

Sometimes you stumble across a delightful artifact. One with an unknown, perhaps unknowable history. Clearly, at one point, it was necessary to hold an object in a particular place, and none of the available clips, clamps, or clasps were up to the task.

A steel rod, an alligator clip, and some electrical tape to the rescue!

What’s fascinating about this isn’t the specifics of the object, but the way that these temporary, stopgap solutions can linger. After enough time and use, they become ordinary and unremarkable. Familiar.

Until, some indefinite period of years later, a fresh set of eyes spots them in an old drawer. Look at what’s in here!

Optical Discs

Stack of DVD-R discs.
Never used, never to be used.

It really wasn’t that long ago that computers came equipped with optical disc drives, and they were effective means of data storage, and the density you could store on a DVD instead of a CD was pretty exciting. Now? They’re not only borderline-useless, but the features that we used to reference as a cultural touchstone are no longer obvious to our students.

It’s not that they don’t know what these are. It’s that they haven’t handled a million of them to know their dimensions, to understand the diffraction rainbow they make. The physicists around here remember using the inescapable AOL discs as cheap, readily available diffraction gratings back in grad school. The astronomers use their proportions to illustrate the shape of the Milky Way Galaxy. Students now need to physically hold one of these to get the idea, because they don’t have a mental image ready to go.

Our Galaxy, if you were wondering, is roughly proportioned as a CD, only instead of being a millimeter and a half thick, is more like 1,000 light years. Very roughly, anyway.