|People in ancient civilizations observed the skies, recognized patterns and stars. They noted the movement of celestial objects, identified constellations, and tracked celestial events.
|Era of Early Astronomy
|Planets and Moon Phases
|Ancient Greeks and other early astronomers distinguished between stars and planets (“wanderers”), noted planets’ retrograde motion, and understood lunar phases.
|The Astrolabe, a sophisticated tool used to measure the position of celestial bodies and to navigate, was refined. It greatly enhanced accuracy in astronomical observation.
|Copernicus proposed the Heliocentric Model, where the sun is the center of the solar system. This challenged the prevailing geocentric belief.
|Early Modern Period
|The telescope was invented, leading to a dramatic increase in the precision of astronomical observations. Galileo made many discoveries, including the moons of Jupiter.
|Isaac Newton developed the law of universal gravitation, which explained the orbits of planets and their moons, laying the foundation for modern physics.
|The science of spectroscopic measurement and analysis was developed, allowing astronomers to determine the composition of celestial bodies.
|Early 20th Century
|Before the 20th century, the Milky Way was believed to be the entire universe. The discovery of other galaxies expanded our understanding of the universe’s size.
|Mid 20th Century
|Expansion of the Universe
|Edwin Hubble’s observations led to the understanding that our universe is expanding, which is a fundamental part of the Big Bang model of cosmology.
|Late 20th Century
|Cosmic Microwave Background Radiation
|The discovery of the cosmic microwave background radiation provided strong evidence for the Big Bang theory.
|Early 21st Century
|Exoplanets Orbiting other Stars
|The first exoplanets were discovered orbiting other stars in our galaxy, leading to speculation about potential life on other planets.
|The direct detection of gravitational waves confirmed a major prediction of Einstein’s general theory of relativity, opening up new ways of observing the universe.