The most visible of the changes will mean that members of the public will be able to enter the site by car from either the east or west gates without the need for visitors' passes. A central corridor of public areas will enable the public to visit much of the Fermilab site, including most of the recreational features of the site. The public areas will be open to the visiting public from 8 a.m. to 6 p.m. from mid-October to mid-April and from 8 a.m. to 8 p.m. when daylight hours are longer. Roadways that are off limits to visiting members of the public will be posted with signs, and motorists will be given site maps to guide them to the public areas.

The public areas will extend into the Lederman Science Center and to the ground floor and atrium of Wilson Hall, and Ramsey Auditorium. Signs will tell visitors which areas of Wilson Hall are open to the public.

"While we have planned carefully for implementing the changes I have outlined, there will doubtless be a learning curve as we put them into effect," said Fermilab Director Michael Witherell. "With your patience and cooperation, I believe that these changes will make our site more welcoming to our neighbors and other visitors without compromising Fermilab's security."

"For me, the breakthrough was the invention of the Michelson Interferometer by A.A. Michelson in 1883," says Kleppner, the Lester Wolfe Professor of

Daniel Kleppner

Physics at MIT. "The interferometer made it possible to measure distances to a small fraction of the wavelength of light. Since a meter typically has a million wavelengths, the resulting precision is enormous."

Kleppner examines the evolution of precision measurements, from the King's thumb to the atomic clock and beyond, in "How Physics Got Precise," the Fermilab Colloquium presentation on Wednesday, January 19 at 4 p.m. in Wilson Hall's 1 West conference room. Kleppner sets the stage with the impressive accuracy of time measurement in early civilizations.

"The Babylonians, about 7000 B.C., and Hipparchus in Egypt, about 150 B.C., knew the length of the year to about 5 minutes," Kleppner says. "The length was found by telling the time of the day of the equinoxes over a long time. If you estimate it to one hour, which is pretty easy, and keep count of the days between equinoxes for twelve years, you have the length of the year to five minutes. Tycho Brahe, in 1600, knew the length of the year to about three seconds."

Kleppner also offers another surprise for post-modern time measurement, involving the re-introduction of human-made or human-related "artifacts."

"For a new generation of atomic clocks," he says, "time keeping could be so precise that the effects of the local gravitational potentials on the clock rates would be important. This would force us to re-introduce an artifact into the definition of the second-specifically, the location of the primary clock."
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