Alpher and Gamow's hot Big Bang

1948MajorContested

Ralph Alpher and George Gamow calculate how light elements formed in a hot early universe. Alpher and Robert Herman predict leftover radiation, later found as the CMB.

Longest chain: The Big Bang → First stars ignite → Supernovae seed heavy elements → The Sun forms → Earth forms → First oceans → First life → Photosynthesis evolves → Great Oxidation Event → Complex cells (eukaryotes) → Multicellular life → First animals → Cambrian Explosion → First vertebrates → Jawed fish → Fish walk onto land → The amniotic egg → The Great Dying → Dinosaurs appear → Asteroid ends the dinosaurs → Early primates → Apes split from monkeys → Human line splits from chimpanzees → Walking upright → First stone tools → Genus Homo appears → Homo erectus → Control of fire → Habitual fire and cooking → Homo sapiens appears → Complex language → Natufian villages → Oldest known bread → Agriculture begins → Irrigation → Uruk and the first cities → Cylinder seals → Writing (cuneiform) → Babylonian mathematics → Babylonian astronomical diaries → Thales and natural philosophy → Trial and death of Socrates → Plato's Academy → Aristotle's Lyceum → Alexander's conquests → Death of Alexander and the Hellenistic kingdoms → Seleucid Empire founded → Parthian Empire founded → Sasanian Empire → Birth of Muhammad → Muhammad's first revelations → The Hijra → Conquest of Mecca → Death of Muhammad and the Rashidun caliphate → Arab conquests → Abbasid Caliphate → Battle of Talas → Paper reaches the Islamic world → House of Wisdom → Ibn al-Haytham's Book of Optics → Bacon's Novum Organum → Royal Society → Papin's steam digester → Newcomen steam engine → Watt's steam engine → Thermodynamics → Conservation of energy → Kinetic theory of gases → Boltzmann's statistical entropy → Quantum hypothesis → Special relativity and E=mc² → General relativity → Lemaître's expanding universe → Alpher and Gamow's hot Big Bang

Contested history

Consensus: The universe expanded from a hot, dense early state about 13.8 billion years ago; the CMB and light-element abundances are the key evidence.

Hot Big BangEstablished

The cosmic microwave background and measured helium and deuterium abundances match its predictions.

Steady state universeDebunked

It cannot explain the cosmic microwave background or the evolution of galaxy and quasar counts over time.