Charles Francis Richter offered him a position as a research assistant there, where he began a collaboration with Beno Gutenberg. The Seismology Lab at the California Institute of Technology wanted to begin publishing regular reports on earthquakes in southern California and had a pressing need for a system of measuring the strength of earthquakes for these reports. Together, Richter and Gutenberg devised the scale that would become known at the Richter scale to fill this need, based on measuring quantitatively the displacement of the earth by seismic waves, as Kiyoo Wadati had suggested. The pair designed a seismograph that measured this displacement and
Order of magnitude An order-of-magnitude difference between two values is a factor of 10. For example, the mass of the planet Saturn is 95 times that of Earth, so Saturn is "two orders of magnitude" more massive than Earth. Order-of-magnitude differences are called decades when measured on a logarithmic scale. Other orders of magnitude may be calculated using bases other than 10. The ancient Greeks ranked the nighttime brightness of celestial bodies by 6 levels in which each level was the fifth root of one hundred (about 2.512) as bright as the nearest weaker level of brightness, and thus the brightest level being