Advent Calendar of Science Stories 16: Undergraduate Research

"You wanted to see me, Herr Professor?"

"Hans! Yes, come in, come in. Just going over the account books. Frightful amount of money going out of this place."

"Well, radium is expensive..."

"Ha! Oh, and speaking of which-- here's one of the sources. Absent-mindedly dropped the fool thing in my pocket last night when I locked up. Terrible habit, I really must work on that. Had a drawer full of the things in Montreal..."

"Thank you. And you wanted to see me about...?"

"Oh, yes. We have a new student, Hans, and I'd like you to put him to work on the gold foil project."

"Shouldn't he have his own project, sir?"

"Not yet, Hans, this one's an undergraduate. Very keen fellow, though. Seems to show some promise."

"Very well. What shall we have him do?"

"Well, first see if he has any aptitude for counting scintillations. If he does, you might have him check for background sources. Check for stray alphas on the same side of the foil as the source, that sort of thing."

"Isn't that futile? We know there won't be any backscattered..."

"True, true. But then, it's a valuable introduction to the frustrations of research, no? Anyway, you never know until you look."

"I suppose."

"Right, then, that's settled. He's in the second-floor common room, or was the last I knew. Come along, and I'll introduce you to young Mr. Marsden..."

I'm running short of days in which to complete all the stories I'd like to tell in this series, so I'm jumping forward almost a hundred years, though staying in England. This totally imaginary scene is set in Manchester around 1908. The talkative fellow in the above bit is Ernest Rutherford, carrying on an imaginary conversation with his post-doc, Hans Geiger.

Rutherford had recently won a Nobel Prize for his work on radioactivity (in Chemistry, ironically, given his famous dismissal of sciences other than physics), and was studying the interactions between the alpha particles and other stuff, specifically a thin foil of gold. They were looking at the deflection of alphas as they passed through the gold, in hopes of learning about the structure of matter. This turned out to be one of the most important experiments in the history of physics, in a very unexpected way. Rutherford hired on an undergraduate student named Ernest Marsden, then 20 years old, and assigned him to the gold foil project.

The detector they were using consisted of a piece of glass coated with zinc sulfide, that would make faint flashes of light when an alpha particle struck. These were viewed through a telescope in a dark room, and it was a very taxing measurement, requiring a long period to allow the eyes to adjust to the dark, and the focus needed to count these scintillation flashes effectively was difficult to maintain. Rutherford himself famously had no patience for it, and the tedium of the counting probably helped inspire Geiger to invent to famous counter that bears his name, as a less irritating means of measuring particle flux. The ability to effectively use these detectors was highly prized, and during Rutherford's time running the Cavendish laboratory, entering students were rigorously screened for scintillation-counting aptitude.

Either because he was good at it, or because they wanted to get him some practice, Rutherford and Geiger set Marsden to looking for flashes from alpha particles on the "wrong" side of the foil. According to the atomic models of the time, there shouldn't've been any to see, as the high-energy alpha particles should've blasted right through the gold. To everyone's shock--Rutherford famously compared it to an artillery shell bouncing off tissue paper-- Marsden saw alpha particles. Lots of them.

The only way this can happen is if the vast majority of the mass of the atom is concentrated in a tiny nucleus at the center, something Rutherford quickly realized, and he introduced the solar-system sort of atomic picture that is the standard cartoon image these days. Of course, such an atom is utterly impossible according to the rules of classical physics, and fixing that problem led Niels Bohr to introduce his quantum model, and physics changed forever.

And it all came out of an undergraduate research project.

Marsden went on to have a very successful career in science, as a professor and administrator in Rutherford's home of New Zealand (some sort of conservation of Ernests involved, perhaps...). Unlike a fair number of other scientists who made revolutionary discoveries at a very young age, he didn't go nuts and start advocating wacky pseudoscience. Possibly because nobody ever won a Nobel for the discovery of the nucleus, something that seems kind of incredible, but comes down to weird Nobel politics.

Anyway, the lesson to take from this is that great discoveries sometimes come from unlikely places. Some project may seem unpromising based on the best models you have, but you never really know until you try it...

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(Part of a series promoting Eureka: Discovering Your Inner Scientist, available from Amazon, Barnes and Noble, IndieBound, Powell’s, and anywhere else books are sold.)

(Rutherford was a fascinating character, and I recommend Richard Reeves's short biography, and also Brian Cathcart's The Fly in the Cathedral about the Cavendish laboratory under Rutherford's direction.)

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