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.
‘Tis that most joyous of days in the beginning of the semester: physics toy kit day! A bag full of odds and ends, perfect for playing, experimenting, and providing tactile bits to use when working through physics problems. Batteries, compasses, various wires, polarizing filters, nails, magnets, and balloons. Always balloons.
Each kit contains two small neodymium magnets, because magnets are amazing. First, you’re bound to stick them together, then spin one around and feel them repel. Surprisingly strong such wee little cylinders. Then check what they stick to around you: whether or not they feel attracted to stainless steel is always intriguing. (The answer is: depends on the type of steel and how it was formed.) Stick them together across a string and let it hang: you’ve built a compass!
Pay attention to the time and location of the sun – or Polaris if you’re pulling an all-nighter – and you can tell which pole of your magnets is which. Maybe it’ll come in handy?
In acoustics, there’s a phenomenon known as beats, which is when two similar tones generate an interference pattern that sounds like a pulsing beat. It happens with waves of all kinds, waves being moving energy and all that, but sometimes it’s easier to really get the sensation when you hear it. Graphing out the sinusoids and showing the constructive and destructive interference helps explain it. Hearing that wubwubwubwubwub cements it.
We have what looks, at first glance, like a glockenspiel, with its metal bars all in a row. Tap one with the mallet, and it sounds almost the same as the one next to it. Almost. Tap two at once, and you get the beats.
At one end, it’s 440 Hz. Then 439, 438, 437, 436, and 435 Hz. Not only can you hear the beats, but you can very clearly hear the change in beat frequency as you combine tones in different combinations. It’s very cool.
Also quite unnerving after a while. woobwoobwoobwoobwoob
It’s only one story up, and not the highest open view on campus, but the view from the top of the Observatory roof is special in one important way: virtually no one else gets to climb up and take in the sights.
On a breezy January day, it’s best to make one’s appreciation brief, sun or no sun. Brrr.
Physicists don’t particularly like bare concrete block walls any more than the rest of us. Lasers: available in a rainbow of eye-searing colors!
(Always practice safety when using lasers.)
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.
Does the mass of a simple pendulum affect its period of oscillation? The small-angle formula doesn’t include mass, just the length from the pivot to the center of mass and g, the gravitational constant. It’s an approximation that’s pretty good for angles up to 15-20°, and after that it’s into introductory differential equations. Which still don’t use the mass, as it cancels out when applying Newtonian mechanics.
That, however, is for an ideal pendulum, with a massless string and point mass bob in a system without friction and other losses. We’re all out of massless string at the moment, and those point masses are proving elusive. And as neat as it might be to swing a pendulum in a vacuum, the setup sounds like a real challenge.
On top of that, it’s an interesting question that’s really addressing a student’s understanding of measurement and uncertainty. Equations and models illustrate principles, and sometimes do an excellent job of making sense of the world. It’s just that the real world is messier, and wading into that mess – even a little bit – can be enlightening.
Two new pendulum masses, machined to the same dimensions, or close enough that you won’t notice without accurate calipers. Threaded to screw on and off. Aluminum (2.7 g/cm³), checking in slightly under 50 grams each. Brass (8.7 g/cm³), a little over three times the mass, a shade above 150 grams apiece. If we can work with the material, we could make more from anything available.
Lightweight plastics, like Delrin acetal (1.4 g/cm³)? Sure. Denser stuff, like lead (11.3 g/cm³)? Not impossible, but okay, well, no. Even denser? Tungsten, gold, and depleted uranium are all in the 19 g/cm³ range. McMaster-Carr has a range of tungsten alloy rods in stock! (For a small fortune.)
For now, though, it’s two masses, a string, and a stopwatch. Real physics in action.
Some storage containers simply have more entertaining labels than others. Case in point: the cardboard box labeled “Astronauts & Space Toys,” which is neither large nor sturdy enough to contain a real astronaut, let alone several.
A find like this is just begging for exploration. We refer to a lot of things around here as “toys,” but these are the real deal.
There are buckets – buckets! – of astronauts inside! Or possibly pieces of astronauts. It’s unclear.
There is a choking hazard warning. One can reasonably assume that choking hazards in space are worse than here on Earth.
The jackpot: toys! Fewer astronauts than advertised, but a substantially higher proportion of Lunar Module Eagles and Hubble Space Telescopes than expected. (Always entertaining to write those as plurals.) Chalk it up in the win column.
If this is how you convince the next generation that astronomy is cool, sign us up.
Frost outside, frozen condensation inside. Welcome to December!
We have many, many compasses scattered about the department. The vast majority come and go as part of the toy kits for PHYS 212, tiny ones useful for illustrating the effects of magnetic fields. Probably more that than for wilderness orienteering. Note: a physics toy kit, despite its educational and entertainment value, is probably insufficient on its own for wilderness survival. Check with the fine folks at Outdoor Education & Leadership for that.
One of the entertaining compass demos is to array a circle of them around an unshielded wire, and seeing the effect of turning the current on and off. Half a dozen little red arrows snapping to attention never loses its neat-o quality.
There’s also this little gem, tucked away in one of our closets. Inscribed with a nice little dedication, reading “TO BUCKNEL / A FRIEND” on the side. Which, the longer you look at it, seems a little less clear each time.
Maybe you had to be there? Interpret it as you will.