Category: Uncategorized

Optical Discs

Posted on by Brian Garthwaite
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.

Carbonized

Posted on by Brian Garthwaite
Bamboo cutting board with large spiral section burnt to charcoal
Oops!

Strange things come through the shop doors some days. This one perfumed the shop for a time, a bamboo cutting board which had been resting on a hot electric coil. Everything smelled like burnt corn husk.

Everything. It was a pervasive scent, intriguing at first and overwhelming after a time.

Bamboo cutting board with a smooth, round divot where the burnt area had been
Looks and smells better.

Scraped, chiseled, sanded, and… well, not exactly like brand new, but in usable shape once again!

Blue Dot

Posted on by Brian Garthwaite
Use blue dots for sure shots!

These are not flashbulbs, merely incandescent A-lamps, but check out the sweet vintage ad!

So the “blue dot” thing was a quality indicator that Sylvania used in their classic flashbulbs. A magnesium filament inside an oxygen environment within the bulb produced a bright flash of light, assuming the envelope hadn’t been compromised. A dot of anhydrous cobalt (II) chloride inside that zero-moisture bulb would remain blue. If there was a leak, atmospheric moisture would react with the cobalt chloride to turn it pink, an indicator that this bulb might not work.

What’s less clear is how, exactly, one wee flashbulb is going to effectively illuminate that whale – flash photography being not super effective at distance – but whatever.

Apollo 13

Posted on by Brian Garthwaite
News release announcing the upcoming Apollo 11 launch in 1970.
We all saw the movie, right?

Fifty-five years ago saw the launch of the Apollo 13 lunar mission, on 11 April 1970. It didn’t go to plan, of course. Things took a bad turn, could have been worse, but who can blame them for optimism in the weeks leading up to it all? Moon science is cool!

Check out that pure 1970 map illustration!

Maps, plans, a pretty tight itinerary. It’s expensive and difficult to go to the Moon, so you don’t waste time. But don’t those hand-drawn maps just make it so inviting? Presumably the astronauts carried maps which were much more detailed and useful, if less likely to get the kid inside all of us super-excited.

Apollo 14 would reach the Fra Mauro highlands in early 1971, though Lovell, Swigert, and Haise never flew into space again.

More Sodium

Posted on by Brian Garthwaite
You’d think it would be more complicated inside.

Here, our more modern sodium light sources, using a clever design that enabled a reduction from the minimum 35W to as little as 18W in 1977. Cool, yeah?

Unfortunately, Philips finally bowed out of the low pressure sodium lamp game in 2019, mean we’ve got these dinosaurs running for as long as we can scour spare lamps online. Once the supply’s gone, it’s gone.

Pure sodium!

Hey, look! Sodium metal! Highly reactive, so it’s inside with a mixture of 99% neon and 1% argon, neither of which deigns to react with, well, anything. That’s why, when it starts up, we see a purplish glow from the noble gases before tube reaches 260°C and vaporizes the sodium. After that, it’s an intense monochromatic yellow-orange that’s hard to look at.

Low Pressure Sodium

Posted on by Brian Garthwaite
Burnt-out low pressure sodium lamp
Toast.

Remember the old, aggressively-yellow street lighting that pre-dated LEDs, ceramic metal halide, and high pressure sodium? Turns out it’s very useful for physics, as the two strong emission lines near 589nm are handy for various experiments.

The lamps themselves are fairly tough, and the ballasts that operate them even more so. But, eventually, they burn out.

General Electric ceased production on these lamps back in 1972. So, no, sorry, replacements are not readily available.

Part 2

Posted on by Brian Garthwaite
Second part of the Math 101 final exam, from November 16, 1948
“End of Test”

It’s part two of our Math 101 algebra final!

Someone really likes to underline for emphasis. They did not want the students to miss that the quadratic formula would be essential for solving 3x2 – 5x + 7 = 0.

Of course, nothing’s as charming as the wiggly, fancily-underlined “End of Test” text. Right?

Part 1

Posted on by Brian Garthwaite
Ditto of Math 101 final exam, part 1, from November 15, 1948
Ditto!

Astronomy, here and elsewhere often under the Physics umbrella, was once part of the Mathematics department at Bucknell. Occasionally, we’ll stumble across some old files in the Observatory that have been yellowing gracefully for decades. Like this two-part final exam from Math 101. Algebra!

Of note for context: this old exam – November 15th, 1948 – waited patiently in a filing cabinet at the current Observatory, built in 1963. In all likelihood, it sat in a folder in the old Observatory for thirteen years, transferred to Tustin Gym for a time, and then quietly continued to be forgotten in a new building until some tech decided to clean the place up a bit.

Who doesn’t love finding curiosities in purple ditto ink?