Quick Recap & Final Jeopardy – March 25, 2016

Today’s contestants:

Sam Gale, a test reader & evaluator from Kernersville, NC

Doug Behrend, a college professor from Fayetteville, AR

Sarah Thompson, an art history professor from Rochester, NY (1-day total: $16,999)

Scores going into Final Jeopardy:
Doug $9,200
Sarah $8,200
Sam $7,000

Final Jeopardy! category: 20TH CENTURY INVENTIONS

Final Jeopardy! clue: In the 1950s physicist Louis Essen built the first practical one of these, noting that it wouldn’t give you the time of day

[spoiler title=’Click/Tap Here for Correct Response’]What is an atomic clock?[/spoiler]

Regarding the clue? Ba-dum-tish! I eventually stopped groaning long enough to put the correct response down to Final Jeopardy.

Meanwhile, From the Royal Society of Chemistry:

Essen learned about the abortive experiments on a visit to Washington in 1950. He returned to the UK convinced that he could build a better clock by combining Rabi’s atomic beam methods with his own quartz timekeeper. He chose caesium because the hyperfine coupling between its single valence electron and nucleus gave a pair of conveniently separated spin states with long lifetimes. He packed a version of Rabi’s apparatus into an evacuated 1.5m tube, with the improvement of Norman Ramsey’s U-shaped microwave cavity providing two excitation regions and thus much narrower signals. The detector was now connected to a clock built from one of Essen’s quartz rings, kept precisely in time by linking it to the rf field in a feedback loop. Any slowing of the ring’s rhythm would pull the rf field off resonance, causing a change in the detected signal and automatically triggering a correction of the beat. His first clock kept time to within one second in 300 years; Essen was so excited that he dragged the director of the NPL [National Physical Laboratory] ‘to witness the birth of atomic time’.

(contestant photo credit: jeopardy.com)

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