• Apr 5, 1054

    Crab supernova explosion

    Chinese and American Indian astronomers observe the Crab supernova explosion
  • Apr 5, 1100

    Lodestone as a Compass

    First known written description of the use of lodestone as a compass
  • Apr 5, 1512

    Heliocentric Theory

    Nicholas Copernicus first states his heliocentric theory in Commentariolus
  • Apr 5, 1543

    De Revolutionibus de Orbium Coelestium

    Nicholas Copernicus publishes De Revolutionibus de Orbium Coelestium (On the Revolutions of the Heavenly Spheres)
  • Apr 5, 1572

    Supernova in Cassiopeia

    Tycho Brahe observes the supernova that appears in Cassiopeia
  • Apr 5, 1577

    Comets are not atmospheric Phenomena

    Tycho Brahe uses parallax to prove that comets are distant entities and not atmospheric phenomena
  • Objects fall at same speed

    Galileo Galilei uses balls rolling on inclined planes to show that different weights fall with the same constant acceleration
  • Empirical Laws

    Johannes Kepler states his first two empirical laws of planetary motion
  • Highly Accurate Pendelum Clock

    Christian Huygens builds the first highly accurate pendulum clock
  • Law of Gravitational Force

    Isaac Newton deduces the inverse-square gravitational force law from the acceleration of the moon
  • Calculus

    Isaac Newton invents his calculus
  • Speed of Light

    Ole Romer uses the orbital mechanics of Jupiter's moons to estimate the speed of light
  • Wavefont Sources

    Christian Huygens states his principle of wavefront sources
  • Inverse Square Law

    Joseph Priestly proposes an electrical inverse-square law
  • Light Can't Escape

    John Michell suggests that some objects might be so massive that not even light could escape
  • Mass of Earth

    Henry Cavendish measures the gravitational constant and determines the mass of the Earth
  • Heat is Energy

    Count Rumford has the idea that heat is a form of energy
  • Electric Battery

    Alessandro Volta announces his invention of the electric battery
  • Absoluter Zero

    Lord Kelvin discovers the absolute zero point of temperature
  • Light is an electromagnetic phenomena

    James Maxwell states that light is an electromagnetic phenomenon
  • Second Law of Thermodynamics

    Lord Kelvin formally states the second law of thermodynamics
  • Special Relativity

    Albert Einstein completes his theory of special relativity
  • Discovery of the Neutron

    James Chadwick discovers the neutron
  • Neutrinos

    Wolfgang Pauli proposes the existence of neutrinos to account for an apparent violation of energy conservation in certain nuclear reactions