Month: November 2022

Compass

Posted on by Brian Garthwaite
Magnetic compass face.
North!

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.

Compass inscription.
Oh. Okay?

Maybe you had to be there? Interpret it as you will.

Tempera powder

Posted on by Brian Garthwaite
Rainbow of tempera powders.
So colorful. So messy.

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.

Bins of colorful sand.
The aftermath.

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…

Vernier calipers

Posted on by Brian Garthwaite
Vernier calipers with purchase date and price.
60 years of precision.

A reliable set of Vernier calipers, still working just fine. We use all manner of measuring calipers around here, with varying degrees of precision for different duties, but it’s nice to see the classics still performing well after six decades. Purchased in April of 1962, for the low, low price of $7.85.

Today’s dollars: $77.46.

“proper cleaning supplies”

Posted on by Brian Garthwaite
Caution label
“Also please wash your hands.”

Do not attempt to clean expensive optical equipment with the same things you use to clean your nose.

Remember: instructions that seem to lay out the most common-sense directives – on signage, in user manuals, in a specification document – are sometimes the result of people actually doing those questionable things.

You can bet someone tried cleaning a telescope’s eyepiece with the handkerchief from their pocket.

Meteoric iron

Posted on by Brian Garthwaite
Meteor.
Big. Heavy.

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.

Widmanstätten pattern
Shiny!