Experts have begun systematically monitoring such unusual phenomena as odd radio noise and spooky lights in the sky in the weeks, hours, and days that precede earthquakes. A light or glow in the sky sometimes precedes a large earthquake, such as the one in 1995 in Kobe Japan, where a white, blue, or orange light was seen by 23 people who reported the sightings. Another sign can be a disturbance in the ultralow frequency (ULF) radio band, which has been seen in the weeks and hours before an earthquake. Researchers at Stanford University documented such signals before the 1989 Loma Prieta quake, which did extensive damage and killed 63 people. There are several theories on how the current causes electromagnetic disturbances. One is that deformation of rock destabilizes atoms and frees a flood of electrons to create positively charged electron deficiencies. Another theory is that the fracture of rock permits ionized groundwater thousands of meters below ground to move into cracks. Resistance of the rock is lowered to create an efficient electric current path. Electromagnetic effects can be detected in various ways, including ground-based sensors and satellites that permit monitoring of noise levels below 300Hz. Among topics covered are information gathered after Loma Prieta, ground based sensor use, using the existing global positioning system (GPS) for earthquake prediction and warning, and the need for a future, working prediction system that will save lives and billions of dollars in damage.