Colloquium: David Griffiths

    Thursday, February 20, 2014 - 3:30pm - 5:00pm
    Meinel 307

    "Hidden Momentum"


    Electromagnetic fields carry energy, momentum and even angular momentum. The momentum density is ε0(E×B), and it accounts (among other things) for the pressure of light. But even static fields can harbor momentum, and this would appear to contradict a general theorem: If the center of energy of a closed system is at rest, then its total momentum must be zero. Evidently in such cases there lurks some other momentum, not electromagnetic in nature, which cancels the field momentum. But finding this “hidden momentum” can be surprisingly subtle. I’ll discuss a particularly nice example.

    Speaker Bio(s): 

    David Griffiths received his B.A. and Ph.D. from Harvard University in 1964 and 1970 respectively. He held postdoctoral positions at the University of Utah and the University of Massachusetts, Amherst, and taught at Hampshire College, Mount Holyoke College and Trinity College before joining the faculty at Reed College in 1978. In 2001-2002 he was visiting professor of physics at the Five Colleges Consortium (Amherst College, Hampshire College, Mount Holyoke College, Smith College and the University of Massachusetts, Amherst), and in the spring of 2007 he was visiting professor of physics at Stanford University. He retired in 2009. 

    Griffiths is a consulting editor of the American Journal of Physics and a fellow of the American Physical Society. In 1997 he was awarded the Millikan Medal by the American Association of Physics Teachers. He has spent sabbaticals at SLAC National Accelerator Laboratory, Lawrence Berkeley National Laboratory and the University of California, Berkeley. Although his Ph.D. was in elementary particle theory, his recent research is in electrodynamics and quantum mechanics. He is the author of 45 papers and four books: Introduction to Electrodynamics (4th edition, Pearson, 2013), Introduction to Elementary Particles (2nd edition, Wiley-VCH, 2008), Introduction to Quantum Mechanics (2nd edition, Pearson, 2005) and Revolutions in Twentieth-Century Physics (Cambridge University Press, 2013).