At its most fundamental level, it is composed of some very simple ideas: expanding gases cool, so the Universe was hotter (and denser) in the past and will be cooler (and less dense) in the future; th...At its most fundamental level, it is composed of some very simple ideas: expanding gases cool, so the Universe was hotter (and denser) in the past and will be cooler (and less dense) in the future; the Universe was simpler in the past, and has evolved complex structures over time as the result of small deviations from homogeneity early in its history; basic gravitational, thermal, atomic and nuclear physics acted on these early seeds to form the structures we see now; this process of evolution …
