PHYS 183 Lecture Notes - Lecture 22: Percival Lowell, Solar Wind, Orbital Period
Document Summary
Venus: similar in mass/radius to earth but different in atmosphere, striking difference in atmosphere. Sulphuric acid in clouds and carbon dioxide vastly most prevalent: temp very hot due to greenhouse effect. Sunlight penetrates atmosphere and heats clouds and surface. Co2 atmosphere opaque to infrared radiation, so heat is trapped, surface gets hotter and hotter. Equilibrium when heat lost via infrared equals that brought in via sunlight. We have greenhouse effect on earth, mostly good. But on the rise by humans: co2 rise 20% since 1700s, suggests global warming, temp since 185- rising, could cause ice caps to melt, oceans to rise, cities to submerge. Venus proof of principle: doppler radar can study venus" rotation: its clouds are transparent to radio waves. Rotation in opposite direction to orbital motion. Sun rises in west, sets in east. Origin not well understood: giant impact, rotation axis still within 3 degrees of alignment, which doesn"t point to giant impact, more on venus.
