  The space-time correlations of streams of photons can provide fundamentally
new channels of information about the Universe. Today's astronomical
observations essentially measure certain amplitude coherence functions produced
by a source. The spatial correlations of wave fields has traditionally been
exploited in Michelson-style amplitude interferometry. However the technology
of the past was largely incapable of fine timing resolution and recording
multiple beams. When time and space correlations are combined it is possible to
achieve spectacular measurements that are impossible by any other means.
Stellar intensity interferometry is ripe for development and is one of the few
unexploited mechanisms to obtain potentially revolutionary new information in
astronomy. As we discuss below, the modern use of stellar intensity
interferometry can yield unprecedented measures of stellar diameters, binary
stars, distance measures including Cepheids, rapidly rotating stars, pulsating
stars, and short-time scale fluctuations that have never been measured before.
