The first observer to catalog differences in star brightnesses was Greek astronomer Hipparchus. He created a catalog around 135 B.C.E. of roughly 850 stars divided into six ranges. He called the ...

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 ...

We know an earthquake is severe when it has a high magnitude number. The 1985 quake that devastated Mexico City was an 8. The quake that shook central Mexico this week was a 7.1. But what exactly is ...

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 ...

Continental transform faults evolve when two plates slide along each other. The most prominent examples are the San Andreas Fault in California and the North Anatolian Fault in Turkey. Earthquakes ...

II.—APPARENT MAGNITUDES: (b) PHOTOGRAPHIC. WITH the application of photography to astronomy it was inevitable that attempts should be made to determine apparent magnitudes by photography. Visual ...