I posted these on Reddit but some questions weren't answered so I was wondering if people here could help: First Part I was informed that the universe did actually exponentially gain energy during inflation and perhaps other periods of its development. So how does this affect the entropy and energy relation above? I assumed since the change in energy is equal to the temperature times the change in entropy that the universe started off as having very low volume, very high temperature/pressure, and low entropy. The high pressure drove the expansion in volume which caused temperatures to decrease and entropy to increase. So that's wrong. But if the inflationary period came with an exponential growth of energy, how did the universe get colder? Was this compensated by a massively exponential increase in entropy? Why do we need something with negative pressure to be responsible for inflation. Wouldn't the extremely high positive pressure with low volume of the initial Big Bang conditions be enough to drive inflation? Second Part I thank you all in advance for any help you can provide in clearing up my confusion! Third Part Regarding this thread: https://www.physicsforums.com/showthread.php?t=506985 Why is the idea that the total energy in the universe "zero" so popular (re: Laurence Krauss) and why is the flatness of the universe used to back this up when, according to that post, an open universe would not conserve energy so the total energy of the universe cannot be "zero", can it? What's the energy being defined as zero and why is that energy used to predict things about the universe when "the" energy (as the term is used in that post) is not zero?