PHYS: Light into matter

Max More (
Thu, 18 Sep 1997 23:29:03 -0700

E=mc^2 formulates the idea that matter can be converted into
light and vice versa. The vice-versa part, though, hasn't been so
easy to bring about in the lab. But now physicists at SLAC have
produced electron-positron pairs from the scattering of two "real"
photons (as opposed to the "virtual" photons that mediate the
electromagnetic scattering of charged particles). To begin, light
from a terawatt laser is sent into SLAC's highly focused beam of
47-GeV electrons. Some of the laser photons are scattered
backwards, and in so doing convert into high-energy gamma ray
photons. Some of these, in turn, scatter from other laser
photons, affording the first ever creation of matter from light-on-
light scattering of real photons in a lab. (D.L. Burke et al.,
Physical Review Letters, 1 September 1997.)

Max More, Ph.D.
President, Extropy Institute:,