PHYS 284 Lecture Notes - Lecture 11: Interstellar Cloud, Fusion Power, Angular Diameter

• School: Concordia University
• Department: Physics
• Course: PHYS 284
• Professor: Mario D'Amico

Document Summary

In the late 19th century, astronomers came up with an idea that seemed more plausible, at least at first. They suggested that the sun generates energy by slowly contracting in size, a process called gravitational contraction (or kelvin-helmholtz contraction, after the scientists who suggested it). Recall that a shrinking gas cloud heats up because the gravitational potential energy of gas particles far from the center of the cloud is converted into thermal energy as the gas moves inward (see figure 4. 15b) A gradually shrinking sun would always have some gas moving inward, converting gravitational potential energy into thermal energy. This thermal energy would keep the inside of the sun hot. (cid:449)hi(cid:272)h (cid:373)ea(cid:374)t that g(cid:396)a(cid:448)itatio(cid:374)al (cid:272)o(cid:374)t(cid:396)a(cid:272)tio(cid:374) (cid:272)ould (cid:374)ot a(cid:272)(cid:272)ou(cid:374)t fo(cid:396) the u(cid:374)"s lo(cid:374)g-term energy generation. With both chemical processes and gravitational contraction ruled out as possible explanations for why the sun shines, scientists were at a loss.