If someone asks you, “How bright is that star?” and your answer is “Pretty bright,” that isn’t very useful. And, of course, it’s worthless for any type of comparative research. So for centuries, ...

There are a number of ways to measure the magnitude of an earthquake. Most scales are based on the amplitude of seismic waves recorded on seismometers. These scales account for the distance between ...

I.—APPARENT MAGNITUDES: (a) VISUAL.THE magnitude of a star, as determined by direct astronomical observation, is a measure of its apparent brightness on a scale which has been precisely defined only ...

where A is the maximum amplitude of deflection of a needle on a chart, in millimeters, measured on the seismograph. A o is an empirical distance correction appropriate for the region (Richter, 1936).