ISCI 101 Lecture Notes - Lecture 12: Ultraviolet, Thermal Energy, Horse Length

• School: JMU
• Department: Interscience Research
• Course: ISCI 101
• Professor: yanjiezhang

Document Summary

4. 5-5 billon years ago, earth"s atmosphere was diferent. 2. 5 billion years ago cyanobacteria began to change atmosphere, produced o2 as a waste product of metabolism. 1. 75 billion years ago, o2 content increased to 21% Form ozone layer to protect life from ultraviolet radiaion. The percent composiion if our atmosphere remains essenially constant with increasing alitude but the density of the atmosphere drops signiicantly as the alitude increases & temperature decreases. Denver (mile high city): 12 lbs/in2 (. 8 atm) Troposphere: region of the earth"s atmosphere closest to earth within 20 kilometers, or ~ 12 miles above sea level. Where weather occurs, jets & aircrats ly here. Stratosphere: the next region in the earth"s atmosphere.