Moment magnitude scale as (in Joules). Unfortunately, the duration of many very large earthquakes was longer than 20 seconds, the period of the surface waves used in the measurement of . This meant that giant earthquakes such as the 1960 Chilean earthquake (M 9.5) were only assigned an . Caltech seismologist Hiroo Kanamori recognized this deficiency and he took the simple but important step of defining a magnitude based on estimates of radiated energy, , where the "w" stood for work (energy): Kanamori recognized that measurement of radiated energy is technically difficult since it involves integration of wave energy over the entire frequency
Magnitude (astronomy) been classified as "stars of the first magnitude". Magnitudes can also be calculated for objects far brighter than stars (such as the Sun and Moon), and for objects too faint for the human eye to see (such as Pluto). Often, only apparent magnitude is mentioned since it can be measured directly. Absolute magnitude can be calculated from apparent magnitude and distance from: This is known as the distance modulus, where is the distance to the star measured in parsecs, is the apparent magnitude, and is the absolute magnitude. If the line of sight between the object and observer is affected