# Meeting Information

## What is Time?

April 24, 2013
American Center for Physics
College Park, MD

Note Change of Date & Speaker: Our scheduled speaker for the April event, Holly Gilbert, has had to cancel her talk to us on April 17. Harold Williams, who spoke to us in March, 2012, has agreed to step in and speak to us on April 24, 2013.

Speaker: Harold A.Williams, Montgomery College, Takoma Park

Topic: What is Time?

Time & Location:  1:00 PM, with Q&A to follow; in a 1st floor conference room at the American Center for Physics, 1 Physics Ellipse, College Park, MD-- off River Rd., between Kenilworth Ave. and Paint Branch Parkway.

Abstract: Time is what clocks measure; all clocks have a mass at rest, rest mass. Mass measures the resistance to acceleration. You know mass is equal to force, pushing, divided by acceleration. Clocks measure the lapse of time by counting repetitions of events like the swinging of a pendulum mass or oscillations of a quartz crystal, movement of the Earth around its axis (a day), movement of the Earth around the sun (a year), or almost any other countable but irreversible movement. Events in the time-space manifold have a nonzero lapsed proper time unless they travel at the maximum speed, the speed of a photon of light in a vacuum. Time answers the question, when is it? Space is about where it is! Clocks measure when; rulers measure where it is! Where and When are not independent questions as Uncle Albert Einstein taught us in the Special Theory of Relativity, SR. Everything is about relationships. Your relatives are important. Time can not be measured except by using an apparatus called a clock that has a nonzero rest mass of at least the size of a flea egg according to Uncle Jano, Eugene Wigner. So time and mass are linked in any measurement even though they are very different things. Time is more fundamental than space, and while you have some freedom in space to go forward or backwards, you cannot go backward in time unless you are made of antimatter. While SR (1905) pops out of electromagnetism as a gift just by understanding light and optics; GR, General Relativity, Uncle Albert's 1915 theory, a theory of gravity, is more complicated and ultimately leads to masses that have rest masses so you can build clocks. Quantum GR is still on the bleeding edge of physics and makes physicist loopy or stringy or just plain tied up in knots. At least that's what it did to me.

Bio: Dr. Harold Alden Williams is the planetarium director and the physics and geology laboratory coordinator at the Montgomery College Takoma Park/Silver Spring campus. He is also an adjunct, contingent, part-time faculty member for Montgomery College. He has taught college classes in three departments: Physical Science (astronomy, geology, and physics), Mathematics (pre-algebra through algebra), and Biology (physical oceanography).

He received his BS in Physics in Physics and Mathematics from the Florida State University, his MS in Physics from the State University of New York (SUNY) at Sony Brook and his PhD in Physics from the Louisiana State University. His PhD dissertation, entitled "Star Formation Using 3-D Explicit Eulerian Hydrodynamics", was supervised by Joel Tohline. He spent two years as a post-doctoral fellow working with Alan Boss at the Department of Terrestrial Magnetism of the Carnegie Institution of Washington.