Mesopotamian ziggurats serve as observatories. Mesopotamian astronomers made careful observations from the tops of pyramid-like towers called ziggurats.
building of stonehenge: used to mark the setting of the sun and solstices
Aristotle argues the celestial bodies are spheres: aristotle used a number of proofs to prove the earth is a sphere and not flat.
Around the year 1000, sundials are prevalent, especially in monasteries where times of prayer were regulated, incorporating greater astronomical and calendrical detail by the later Middle Ages and Renaissance.
Copernicus publishes "De Revolutionibus". De Revolutionibus, Copernicus's description of his heliocentric model of the solar system, was published two months before his death
Tycho carries out best pre-telescopic observations ever. Tycho's observations, made using specially built instruments, were the most accurate ever made with the naked eye
In 1608 in the Netherlands, Hans Lippershey, a Dutch spectacles maker, invents the telescope.
From 1609-1632, Galileo uses the telescope to observe the sun, moon (discovered that the moon had valleys, mountains, and plains like Earth does), phases of Venus, the four large satellites of Jupiter (proof that celestial bodies didn’t orbit the Earth), and published “The Dialogue”.
1610: Kepler discovers laws of planetary motion. Working with Tycho's observations, Kepler discovers the shapes of planetary orbits, how the speed of a planet varies as it orbits the Sun, and the relationship between orbital distance and orbital period
In 1659 in the Netherlands, Christiaan Huygens discovers Saturn’s rings and Titan (the fourth satellite of Saturn).
In 1675 in France, Danish astronomer Ole Romer measures the speed of light while in Paris.
In 1905 and 1916 in Germany, Albert Einstein introduced his special Theory of Relativity in the paper Electrodynamics of Moving Bodies (1905) and his general Theory of Relativity (1916).
In 1957 in Russia, Sputnik is launched, making it the first object to orbit the Earth.
In 1969, Neil Armstrong and Edwin “Buzz” Aldrin walk on the moon on the Apollo 11 Mission.
In 1992 in Vatican City, The Vatican under Pope John Paul II announces that the Catholic Church was wrong about condemning Galileo’s work that proved that the planets (including Earth) revolved around the Sun, not the Earth.
In 2006, Pluto was declassified as a planet and was instead classified as a dwarf planet.