Monthly Archives: May 2008

New Exhibit at the Physics Museum

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The gallery of failed atomic models, 1903-1913 from Skulls in the Stars.

[H]ow many atomic models were there?

A lot. Most people in physics are taught Thomson’s ‘plum pudding’ model of the atom, but a little investigating turned up no less than eight distinct pictures of atomic structure.

The late 1800s and early 1900s was the breakthrough period of atomic research. A number of tantalizing pieces of experimental evidence suggested a nontrivial internal structure to the atom.

We are taught (and teach) the Bohr model because it has some use, even though it is wrong/incomplete. But it’s useful to remember that in the presence of fragmentary information there are going to be failed attempts at explaining the underlying phenomenon. As more data is uncovered the false theories can be weeded out, because they will not have predicted the event or will have predicted a phenomenon that was never observed, despite a reasonable expectation of doing so.

Toys in the Office: Gettin' Medieval

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trebuchet.jpg

Bought this trebuchet as a kit several years ago, and put it together over the Memorial day weekend back then. I had seen a NOVA special about some men who built two using in-period tools, and then knocked down a wall with them. When I ran across the kits on the intertubes, I couldn’t get my wallet out fast enough. It came with what looked to be ~50 caliber musket shot, which is not exactly conducive to indoor testing, so I substituted balled-up aluminum foil. It’s a favorite of some visitors, including the safety inspector(!).

Here’s a Trebuchet Challenge for testing your mad siege engine skillz.

"Classic" Timekeeping, Part I: Introduction

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Following the suggestion and subsequent reminder (nothing like a deadline to get the creative juices flowing) from gg at Skulls in the Stars, I’ve got two “old” papers that I’m going to summarize.

I recommend choosing something pre- World War II, as that was the era of hand-crafted, “in your basement”-style science. There’s a lot to learn not only about the ingenuity of researchers in an era when materials were not readily available, but also about the problems and concerns of scientists of that era, often things we take for granted now!

These are from 1931, fulfilling the pre-WWII criterion, when you still had individuals engaging in research that were self-financed or supported by a patron and much of the equipment was self-manufactured. The science in this case was largely self-funded, and as for the “basement,” well, it’s a pretty fancy basement as you’ll see, as one might suspect of someone who can fund his own science. But classic nonetheless. There’s a bit to do, and I’m going to break it up into more manageable chunks.

The papers in question are from the Monthly Notices of the Royal Astronomical Society, Vol. 91, published in 1931, and are “The Precise Measurement of Time” by Alfred L. Loomis (p. 569-575) and “Time, Analysis of records made on the Loomis chronograph by three Shortt clocks and a crystal oscillator” by Brown, E. W. & Brouwer, D. (p.575-591). (I, know, I know. They sound like tabloid headlines, don’t they?) The first paper describes various apparati used, and the second describes a particular measurement that was of interest to me.

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Richard Feynman and The Connection Machine

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Richard Feynman and The Connection Machine

Story of Richard Feynman working at Thinking Machines.

Many a visitor at Thinking Machines was shocked to see that we had a Nobel Laureate soldering circuit boards or painting walls. But what Richard hated, or at least pretended to hate, was being asked to give advice. So why were people always asking him for it? Because even when Richard didn’t understand, he always seemed to understand better than the rest of us. And whatever he understood, he could make others understand as well. Richard made people feel like a child does, when a grown-up first treats him as an adult. He was never afraid of telling the truth, and however foolish your question was, he never made you feel like a fool.

via Daring Fireball

Beulah, Peel Me a Piece of Copy Paper

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The surprisingly rich physics of peeling paper

[T]he physics of peeling paper almost exactly mimics the stick-slip movement of tectonic plates, right down to the statistics of the time between “quakes” and the correlations between released energy and aftershock activity.

From the preprint, “Line creep in paper peeling:”

For paper, we use perfectly standard copy paper, with an areal mass or basis weight of 80 g/m2. Industrial paper has two principal directions, called the “Cross” and “Machine” Directions (CD/MD). The deformation characteristics are much more ductile in CD than in MD, but the fracture stress is higher in MD [20]. We tested a number of samples for both directions, with strips of width 30 mm. The weight used for the creep ranges from 380 g to 450 g for CD case and from 450 g to 533 g for MD case.

I’ll never look at copy paper the same way again.

It'll Do, But I Wanted a Frikkin' Laser

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An electric fly-swatter, over at Built on Facts

Press the button on the side and swing it at the fly in the air; there’s a spark and a pop, and the fly falls out of the sky like a little brick. No mess, and dementedly entertaining (I’ll admit it). Yeah it’s a little redneck, but effectiveness is effectiveness.

Redneck? Surely you jest. What is needed now is a little empirical testing, a la Colbert’s fun with a spark coil.

Safety Tips

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As if a physicist fence could keep us out or in.

He informs me that it is actually a “physicist fence” which is used to keep the physicists on campus and prevent them from roaming free in the community and administering random physics lessons to unsuspecting citizens.

Don’t forget: we know how to tunnel. We learn that in quantum mechanics.

No, the best way to keep us from administering random physics lessons is to provide us with fun toys like lasers and vacuum systems to keep us occupied, to not make eye contact, and say nothing to encourage us (questions or leading statements).

True story: last week, out at lunch, one of the gang (not a physicist) got two containers of cream for his coffee. He mused, out loud, “I wonder if they have the same volume?” He then emptied one into his cup, and put the other one down! How do you ask the question and then not follow through? I opened the second and emptied it into the first, and confirmed that they were the same volume.

So, avoid things like that, or “I wonder how that works,” or baiting us with obviously wrong statements (“It swirls that way because of the Coriolis force” or “Relativity is crap”). And don’t attempt nerd sniping.