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Science Night Live with Brian Saam

Wednesday, Nov. 19 @ 5:30 p.m. - Science Night Live! with Brian Saam. "A History of the Second: From Grains of Sand to Atomic Clocks" at Keys on Main (242 South Main Street, Salt Lake City, UT).

SCIENCE NIGHT LIVE

with Dr. Brian Saam,
Professor of Physics & Astronomy

A History of the Second: From Grains of Sand to Atomic Clocks

Date & Time: Wednesday, Nov. 19, 2014. 5:30 - 7:00 PM

Location: Keys on Main (242 South Main Street, Salt Lake City, UT)
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Without getting too deep into existential philosophy,we can begin a discussion of time with an operational definition: time separates cause from effect; more precisely, time delineates the order of events. Our earliest human ancestors recognized that to measure time, one needs a periodic event that is easily, reliably, and universally observed in exactly the same way. Both the rotation of the Earth on its axis and revolution of the Earth about the Sun satisfy these requirements and have been universally accepted time standards throughout most of recorded history. Every timepiece ever invented prior to 1967—sundials, water clocks, hourglasses, and mechanical clocks—traced its calibration in some way back to the apparent motion of the sun in the sky. However, as robust and reliable as this standard appears (the Earth’s rate of rotation slows by about 1 second in 60,000 years), it is inadequate for the modern frontiers of scientific discovery, as well as for the needs of a global telecommunications and geo-positioning infrastructure. A much more stable standard was developed starting in the 1960s that is based on a transition that occurs between two specific energy levels in atomic cesium. These “atomic clocks” are stable to about 1 second in 30 million years. Work on even more stable clocks (1 second in 30 billion years) is at the frontier of modern atomic physics.

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