Cosmic Expansion Slowdown Speedup and the Big Bang Theory

Comparing observation and the Big Bang theory, observation tells us that the early universe, over a period of about 3.3 bly, consisted of radiation which later evolved into the galactic system we observe today. The Big Bang theory tells us that the early universe began about 15 bly ago as an initial expansion from nothing forming subatomic particles which lasted for a short time, fewer than 0.4 bly and later evolved into the present system.
Based on Hubble’s linear law v=Hr, space expansion ...