The Canadian Nuclear FAQ   by Dr. Jeremy Whitlock www.nuclearfaq.ca

Published in the December 2013 issue of the Canadian Nuclear Society Bulletin, Vol.34, No.4.

Snow Country for Old Men

by Jeremy Whitlock

This Christmas marks the 75th anniversary of one of the most famous "walks in the snow" in history.

The universe, and the laws of physics that govern it, lay before Lise Meitner as enigmatic and beckoning as the snowy Swedish landscape. An Austrian-born Jew, Meitner was not enjoying her refugee life in Stockholm. She had never stopped thinking about the mysterious uranium-neutron reaction that she and Otto Hahn had struggled with before her flight from Hitler's Germany earlier that 1938.

Hahn himself continued to look to Meitner for a brilliant explanation that had evaded science's best and brightest for four years now - even the great Enrico Fermi himself, who performed the initial experiment in 1934. Fermi knew then, as everyone knew, that adding a neutron to nature's heaviest element would lead to an uncharted world of transuranic wonder: creating super-heavy elements that hitherto only nature herself had played with briefly.

Even some timely out-of-the-box thinking by another woman scientist at the time couldn't dissuade the scientific elite from its march to glory: Ida Noddack, a chemist of no small repute herself (co-discoverer of the element rhenium in 1925) had criticized Fermi's results in 1934, pointing out the possibility that the neutron-bombarded uranium could instead have broken into "several large fragments". Being a woman, and a chemist, and failing to provide theoretical backup to her lateral thinking, she was ignored (and how differently World War II might have progressed otherwise...).

On Christmas Day 1938, Lise Meitner clutched in her hands evidence that she could expect to be treated a little better: a desperate letter from Otto Hahn, begging her to come up with something brilliant to explain what he had now proven - that one of the products of Fermi's famous neutron bombardment of uranium was, in fact, barium. But how could something half the mass of uranium result from adding something as inconsequential as a neutron? Unlike 1934, it was now chemistry asking physics for an answer.

With Meitner was her nephew, Otto Frisch, another refugee Jewish physicist. The two had met up at a friend's home in Kungälv for the Christmas holidays, and now struck out on a bracing walk in the snow - and into the history books.

Frisch on skis, with Aunt Meitner trudging alongside, talked about Hahn's conundrum - more than a conundrum: a constipation of science four years old. Perhaps it was the clarifying embrace of the wintry air, or perhaps the mental unschackling of refugee life, or perhaps the non-linear insight of the gentler gender that had been advancing nuclear science since Marie Curie - somewhere in the Swedish snow the light went on.

Surrounded by frozen liquid drops, Meitner speculated whether the relatively new "Liquid Drop Model" of the nucleus might explain a single neutron inducing oscillations in a uranium nucleus, causing it to break up. Energy would be liberated in the process, and thanks to Einstein they were able to estimate how much: the answer quite literally stopped them in their tracks.

The rest, as they say, is history. Frisch went on to experimentally prove the process, which he coined "fission". Otto Hahn went on to receive a Nobel Prize, downplaying for the rest of his life the role of Lise Meitner - now seen as one of the biggest oversights in Nobel Prize history.

There have been other famous "walks in snow" in history. Pierre Trudeau's legendary midnight stroll in an Ottawa snowstorm in 1984 led to his decision to retire after 15 years as Prime Minister. Hitler without a doubt took a snowy stroll or two around his Führerbunker that final winter of 1945 before deciding to end it all.

Lesser known is the frigid stay of a small group of chemists for the National Research Council, who camped that first winter in 1944 at what would soon become Chalk River Nuclear Laboratories, with orders to design the water treatment plant for the reactors to come. Socked in with few supplies, alone, and freezing, they likely took more than a few strolls in the snow to question their respective decisions to become government scientists.

Stay warm, and Merry Christmas.

Discussion welcome.

©2013 Jeremy Whitlock