Discoveries in the Physics & Astronomy shop | Science, curiosities, and surprises
For the most part, deciding on constellations is hard. A few really stand out (Orion, Cassiopeia) as do a number of bold asterisms (the Big Dipper in Ursa Major, the Teapot in Sagittarius). The rest of the sky, where there are stars but no super-obvious pattern stands out? Oof.
Picking all 88 sounds like a beastly challenge.
Still… sometimes it seems like someone just starting phoning it in in the end.
Declaring Norma to be a carpenter’s square isn’t helping your case.
There’s a funny thing about important scientific discoveries. The effort and time and careful data collection and building atop previous understandings and innovations and everything else is daunting, difficult, and a massive undertaking. Critical details and a fine understanding may take months, years, or entire careers. A general grasp, though?
Sometimes, you can explain the gist of things with stuff that’s just lying around.
Hubble’s Law, also known as the Hubble-Lemaître Law, describes the expansion of the universe. Galaxies are moving away from ours, and the further away they are, the faster they’re moving. Getting there relied on the Friedmann equations – themselves built upon Einstein’s general relativity – plus Slipher’s redshift measurements of distant galaxies, plus the debates between Shapley and Curtis, plus an understanding of the relationship between luminosity and period in the pulsations of Cepheid variable stars. (They’re like the drinking bird toys of stars.) Plus more, and more, but you get it. A lot goes into explaining the expansion of the universe when all you’ve got is a telescope and spectrometer.
Hubble ran into a real hiccup here. If everything in the universe is moving away from us, and we can correlate the distance and speed in any direction, doesn’t that imply that we’re at the center of the universe? Turns out, no. We’re not.
And you can illustrate the principle with a Slinky, a ruler, and some paper clips.
We get a lot of mileage out of the Slinky.
When astronomers study objects they can’t reach, they’re typically limited to visual clues to glean information. Sometimes that’s color variation, like when the ejecta from a crater redistribute layers of rock and soil. Laid down at different times, and made of different materials, the dark and light rings and patches can provide a great deal of insight into how and when a lunar crater formed, for example.
The moon is somewhat less vividly colored than a sink full of tempera paint powder, of course. Electroshock hues make the distinctions easier for the students. We have black, brown, and white in the mix. They work just as well, but never elicit the excited reaction of a brilliant orange or a neon-level magenta.
Intended for mixing your own paint, these are effectively the same as the bright, thick paints in nearly every kids’ art classroom you’ve ever seen. Combined with the play sand, the whole lab starts to smell a little bit like a fun day at preschool.
In the end, it all becomes a smeared, brownish-gray mix of sand, pigment, and the occasional lost marble or ball bearing. That and a room where every horizontal surface has a new layer of fine, fine dust…
You know what makes great examples of craters in a lab setting? Play sand. Powdered tempera paint. Slingshots. A variety of round projectiles.
It’s going to be a spectacular mess next week.
The moon enters totality, as viewed from the SkyCam, 4:55 to 5:20 am. Not nearly as cool as in person, but eclipses are always cool.
Meteorites – those shooting stars which don’t completely burn up entering our atmosphere and then crash to the ground – can be made of all sorts of stuff. The most commonly found in museums and collections are metallic, not because they’re the most frequent type of meteorite, but because they’re the most likely both to survive entry/impact and to be discovered. A stony meteorite might look remarkably like an ordinary rock. A big chunk of warped iron just sitting on the ground? Slightly more conspicuous.
We have a few meteorites and pieces of meteorites on display, including this big slab. Cut, polished, and given an acid treatment, it shows off its internal crystalline structure. Primarily iron and nickel in two different crystalline shapes, it has a characteristic pattern known as a Widmanstätten pattern. Given a sufficiently long cooling period to enable crystal formation – typically on the order of millions of years – it produces this distinct appearance that highlights its extraterrestrial provenance.
Can’t do this stuff in a lab is what we’re saying.
The acid-etching process enhances the pattern where the high-nickel taenite alloy is more resistant to the acid than the low-nickel kamacite, turning a smooth, polished surface into one that looks, well, really cool.
Astronomy is roughly 98% figuring out how to look at stuff better than our eyes can do it.
Gathering more light with large-aperture lenses and reflectors. Gathering more light with long camera exposures. Using detectors for light outside the visible spectrum, from radio waves to gamma rays. Launching telescopes a million miles into space to get away from our pesky atmosphere. Splitting the broadly blended colors we perceive into their component wavelengths.
That last one’s the easiest to accomplish in a student lab setting, and it’s a broadly useful scientific tool across many disciplines. Turns out that certain particular constraints caused by quantum physics make all sorts of other observations possible. Who knew?
Pictured above is a low-pressure sodium lamp, just like the ones that once illuminated nighttime streets around the world with their flattening orange glow. Looks orange to our eyes, but it’s primarily a mix of red, orange, and yellow wavelengths. If you measure those carefully enough, you can discern a certain “fingerprint” on a spectrum of light that would tell you if sodium is or isn’t present in what you’re observing.
Same applies to hydrogen and helium. Nitrogen and oxygen. Argon and neon. Carbon dioxide. Water. Every atom and molecule – including different ionized states, which is a particularly useful bit of information for astronomers – has its own unique spectrum of light it emits. You just need to look at it in the right way.
Even if it’s millions of light-years distant.
A great many jobs in the daily work of a shop consist of riffs on this: can you make item A connect to item B? It might be physical connections, electronic and/or digital signals, or even the relatively abstract interpretation of transitioning a lab space over from one experiment to the next without disruption. The simplest ones are when someone can’t locate the proper connector cable. (There are so many different kinds!) Less simple are those times when two things are supposed to fit, but don’t.
Just straight-up don’t.
At the Tressler lab, we have the luxury of permanently-installed piers which support our telescope mounts. For our purposes, this is an excellent improvement over the default, a very stable yet heavy tripod. Now in the process of upgrading our mounts, we find that the tapped mounting holes on the pier don’t match the drilled and counterbored corresponding holes on the custom-made mount adapters. By 1/8″ or more in some cases. Sounds small. Is actually huge. Is will-not-fit-even-with-brute-force huge.
Note: not made in-house. We could try to guess where the error might have arisen, but our job is to fix it.
Also note: the previous mounting plate was not precisely machined to the proper dimensions, either, but was close enough that it was fastened by brute force. Sensing a theme here, which is this: precise measurements are crazy hard.
Getting to the adapter-for-the-adapter called for more than one CNC-milled plastic prototype. Measure, mill, test. Rinse, repeat. Polyethylene, as one might imagine, is cheap stuff.
A few test runs later, we have a custom-machined (in-house!) sheet of 1/2″ aluminum to connect to the 5/16″-18 tapped holes on the pier, which then sets up a new series of 1/4″-20 holes in this plate and the mount adapter to hold everything rock solid. Holes drilled and tapped, counterbored for a clean surface with all of those socket screws.
And all carefully measured and aligned on the milling machine to within 0.001″.
You don’t appreciate the precision of reliable machinery and sharp tooling until the pieces slip together effortlessly. Whoa! Goosebumps!
Best part? The adapter is functionally invisible for anyone who doesn’t know to look for it. Few things feel as rewarding as solving a problem before (almost) anyone else realizes it’s there.
The Clark, our lovely 19th-century telescope. Much to be written on it another time, but here’s a picture with the dome open on a fine, sunny day.
Just look at that lovely brass set against the black steel tube. Magnificent.
Astronomy can be awkward. By necessity, observation happens at night. (Mostly.) And outside, in whatever weather permits clear skies. Hot and humid or bitter cold, the telescopes only function when they’re at equilibrium with the air around. When the temperature drops so low that the grease in the motorized mounts thickens, we call it quits, but nights reaching down to about 20°F are fair game. Precipitation always shuts things down, as does substantial cloud cover.
What to do when you’re at home, all warm in your jammies, and not sure if it’s worth trekking out into the cold? Check the Bucknell University Sky Camera website, of course. If it looks like this:
Visible stars, no serious cloud cover: you’re good to go. The bright spot in this particular image is probably Saturn, but you get the idea. If you can see it here, you can see it through a telescope. Checking the weather forecast is fairly reliable, although it gets dicey around those transition zones between “good enough” and “should have stayed home.” Forecasts also describe cloud cover in terms of percentage obscured, without a distinction between sparse-but-dense and widespread-and-gauzy.
Depending on what you want to accomplish, sometimes clouds are something you can work with. Astrophotography? Visual observation? Naked eye and constellations? Sometimes, here in a Pennsylvania river valley, you shrug and make it work.
(The alternate method is to walk outside and look up – quite reliable, that – but maybe not ideal if you’re in the aforementioned jammies.)
The skycam can also be entertaining to check during the daytime. You can watch the sun track across the ecliptic and see the discrepancy between clock time and solar time during Daylight Saving Time. On a cloudy day, sometimes the clouds themselves are just plain neat. Raindrops. Snow accumulating. Snow melting. Birds and bugs and all sorts of things captured by intermittent photography.
Including the occasional technician out on maintenance duty. Wave hi!