-
276 BCE
Eratosthenes measures Earth’s circumference
Using the angles of shadows in two different locations, he estimated Earth’s size with remarkable accuracy, proving that Earth is a sphere. -
140
Ptolemy develops the geocentric model
In his book Almagest, he proposed that Earth was the center of the universe, a belief that dominated astronomy for over 1,400 years. -
1543
Nicolaus Copernicus proposes the heliocentric model
In De revolutionibus orbium coelestium, he argued that the Sun, not Earth, was at the center of the universe, challenging Ptolemy’s model. -
1572
Tycho Brahe observes a supernova
His detailed astronomical observations proved that the heavens were not perfect and unchanging, contradicting Aristotelian ideas. -
Johannes Kepler formulates his First and Second Laws of Planetary Motion
Kepler’s laws described how planets move in elliptical orbits rather than perfect circles and that they speed up when closer to the Sun. -
Galileo Galilei uses a telescope to make groundbreaking discoveries
He observed Jupiter’s four largest moons, proving that not everything orbits Earth, and saw the phases of Venus, which supported heliocentrism. -
Isaac Newton publishes Principia Mathematica
Newton’s work explained gravity as the force that governs planetary motion, unifying celestial and earthly physics under the same laws. -
William Herschel discovers Uranus
Using a telescope he built himself, Herschel found Uranus, the first new planet discovered in modern times, expanding the known solar system. -
Johann Galle & Urbain Le Verrier discover Neptune
Le Verrier mathematically predicted Neptune’s existence based on Uranus’ orbital irregularities, and Galle confirmed its location with a telescope. -
Albert Einstein develops the Special Theory of Relativity
His theory revolutionized our understanding of space, time, and gravity, laying the foundation for modern cosmology. -
Karl Schwarzschild describes black holes
Using Einstein’s equations, he proposed the existence of black holes, objects so dense that even light cannot escape their gravity. -
Edwin Hubble discovers the expansion of the universe
By observing redshifts in distant galaxies, he found that the universe is expanding, leading to the development of the Big Bang Theory. -
Clyde Tombaugh discovers Pluto
While searching for a ninth planet, Tombaugh found Pluto, though it was later reclassified as a dwarf planet in 2006. -
Neil Armstrong & Buzz Aldrin become the first humans on the Moon
During the Apollo 11 mission, Armstrong famously declared, “That’s one small step for man, one giant leap for mankind.” -
Carl Sagan helps launch the Voyager probes
Voyager 1 and 2 were designed to explore the outer planets and continue to send data from interstellar space today. -
Michel Mayor & Didier Queloz discover the first exoplanet
They detected 51 Pegasi b, proving that planets exist outside our solar system, revolutionizing astronomy. -
Pluto is reclassified as a dwarf planet
The International Astronomical Union (IAU) redefined what it means to be a planet, downgrading Pluto and classifying it as a dwarf planet. -
The Event Horizon Telescope captures the first-ever image of a black hole
A global network of telescopes created a groundbreaking image of the black hole at the center of the galaxy M87. -
The James Webb Space Telescope (JWST) is launched
As the most powerful space telescope ever built, JWST is designed to study the earliest galaxies and search for habitable exoplanets. -
Spacex Starship successful earth landing
Elon musk perfects the first completely reusable spaceship