Look up statistical mechanics
i found this from university of texas. Thermodynamics & Statistical Mechanics:
http://farside.ph.utexas.edu/teaching/sm1/statmech.pdf
"Many people are drawn to Physics because they want to understand why the
world around us is like it is. For instance, why the sky is blue, why raindrops are
spherical, why we do not fall through the floor, etc. It turns out that statistical
thermodynamics can explain more things about the world around us than all
of the other physical theories studied in the undergraduate Physics curriculum
put together. For instance, in this course we shall explain why
heat flows from
hot to cold bodies, why the air becomes thinner and colder at higher altitudes,
why the Sun appears yellow whereas colder stars appear red and hotter stars
appear bluish-white, why it is impossible to measure a temperature below -273
centigrade, why there is a maximum theoretical efficiency of a power generation
unit which can never be exceeded no matter what the design, why high mass
stars must ultimately collapse to form black-holes, and much more!"