CAS AS 100 Chapter Notes - Chapter 14: Radiation, Angular Diameter, Photosphere
19 May 2016
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14. 1 gravitational contraction: early astronomers thought that the sun generates energy by slowly contracting in size (kelvin helmholtz) A gradually shrinking sun would always have some gas moving inward, converting gravitational potential energy into thermal energy, keeping the inside of the sun hot. Because of its large mass, the sun would need to contract only very slightly each year to maintain its temp. However, geologists pointed out that studies of rock and fossils showed that earth was way older than 25 million years (which is how long the sun would shine with this theory) His equation of e=mc^2 proved that mass itself contains an enormous amount of potential energy. Calculations proved that the sun"s mass contains more than enough energy to account for billions of years of shining if sun converts energy of mass to thermal energy. Sun converts mass into energy through nuclear fusion.
