History of Astronomy

  • 384 BCE


    Aristotle (384-322 B.C., Greek), the great philosopher, proved that the Earth is spherical, and believed that it was at the center of the universe. He knew that if the Earth revolved around the Sun, then we should see the stars shift position throughout the year. Since he did not have the technology to detect this shift, as we do today, he concluded that Earth must rest at the center of the universe. According to him, the planets and stars were located in spheres that revolved around the Earth.
  • 190 BCE


    Greek astronomer and mathematician who measured how far the moon was from the Earth using trigonometry. He also worked on finding out if the Earth revolved around the Sun or vice versa.
  • 100 BCE

    Ptolemy/ Ptolemaic Model

    Ptolemy/ Ptolemaic Model
    Ptolemy lived from 100 AD to 170 AD. He created the Ptolemaic Model, which is a geocentric cosmology; that is, it starts by assuming that the Earth is stationary and at the center of the universe.
  • Period: 1473 to 1543

    Nicolaus Copernicus: the Heliocentric Model

    Nicolaus Copernicus suggested that Mercury, Venus, the Earth, Mars, Jupiter and Saturn all revolve around the sun. The moon is the only celestial sphere in this system which revolves around the earth, and together they revolve around the sun. Copernicus' model of the solar system is the one we know today. He also created the Scientific Method of Investigation.
  • 1546

    Tycho Brahe

    Tycho Brahe
    Danish astronomer whose observations—the most accurate possible before the invention of the telescope—included a full study of the solar system and accurate positions of more than 777 fixed stars, and what he accomplished remains today.
  • Period: 1564 to

    Galileo: Jupiter's Main Moons

    Galileo was an Italian astronomer. He was the very first person to discover sunspots. In a very short time, Galileo discovered Jupiter's four largest moons — Io, Europa, Ganymede, and Callisto, now called the Galilean moons. The four Galilean moons were the first celestial bodies to be discovered with a telescope.
  • 1571

    Johannes Kepler

    Johannes Kepler
    Johannes Kepler, working with data painstakingly collected by Tycho Brahe without the aid of a telescope, developed three laws which described the motion of the planets across the sky.
  • Hans Lippershey

    Hans Lippershey
    Hans Lippershey was a spectacle maker from the United Netherlands. He was traditionally credited with the invention of the telescope in 1608.
  • Giovanni Cassini

    Giovanni Cassini
    Italian who discovered the rings of Saturn. 4 of Saturn's moons, and the rotation periods of Mars and Jupiter.
  • Period: to

    Sir Isaac Newton

    Isaac Newton further developed works of Copernicus and Kepler using math. Invented reflecting telescope 1668. He created the 3 laws of motion.
  • Difference Between Refracting and Reflecting Telescopes

    Difference Between Refracting and Reflecting Telescopes
    A reflector telescope uses two mirrors instead of two lenses. The job of the objective lens, opposite the eyepiece end, is to gather the light coming from a distant object, such as a star, and bend it into a single point of focus.A mirror used to gather light doesn’t suffer from this effect. Light from an object enters the telescope tube and is reflected off a curved mirror at the end of the tube.
  • William Herschel

    William Herschel
    Discovered the planet Uranus and its moons. He also discovered 2 more of Saturn's moons. Believed to have polar ice on Mars leading to the studies hoping to find water on Mars. IN 1800 he performed a simple experiment determining the temperature of the different colors of sunlight passed through a prism. He discovered the cause of the rainbow.
  • Percival Lowell

    Percival Lowell
    Discovered that planet Pluto and studied the "canalis" on Mars. Built the Lowell observatory in Flagstaff, AZ to study Mars.
  • Period: to

    Ejnar Hertzsprung

    One of the inventors of the Hertzsprung_Russel diagram. The HR diagram shows the correlation between the absolute magnitude (brightness) and the spectral type of star.
  • Period: to

    Albert Einstein

    Theory of Relativity (1905) and gravitation.
  • Period: to

    Edwin Hubble

    Using the color of the stars, discovered the universe is expanding. Hubble’s Law, galaxies are moving away from each other. The idea is the basis of the Big Bang Theory of how the universe began.
  • Period: to

    Karl Jensky

    American engineer whose discovery of radio waves from an extraterrestrial source inaugurated the development of radio astronomy, a new science that from the mid-20th century greatly extended the range of astronomical observations.
  • Period: to

    John Glenn

    John Glenn was a NASA astronaut. He was part of the first group of astronauts NASA picked. He was the first American to orbit Earth. He also became a U.S. senator. Later, he became the oldest person to fly in space.
  • Yuri Gagari

    Yuri Gagari
    In 1961, Russian cosmonaut Yuri Gagarin became the first human in space, making a 108-minute orbital flight in his Vostok 1 spacecraft.
  • Sputnik Launch

    Sputnik Launch
    in 1957 the Soviet Union launched the world’s first artificial satellite.That launch ushered in new political, military, technological, and scientific developments.
  • Apollo Missions (Apollo Program)

    Apollo Missions (Apollo Program)
    This was the mission that landed Neil Armstrong on the moon. There were 17 in all.
  • Neil Armstrong

    Neil Armstrong
    Was the first man to walk on the moon in 1969. He said the infamous phrase: “That’s one small step for man, one giant leap for mankind”. He represented America.
  • First Space Shuttle Flight

    First Space Shuttle Flight
    Space Shuttle Columbia went into orbit from NASA's Kennedy Space Center in Florida. Astronaut John Young commanded the mission. Most of the shuttle was used, except the engine, which burned up.
  • Mars Pathfinder Expedition

    Mars Pathfinder Expedition
    It was designed as a technology demonstration of a new way to deliver an instrumented lander and the first-ever robotic rover to the surface of the red planet. Pathfinder did this and also gave much more information than expected.
  • Cassini Orbiter (Cassini-Huygens)

    Cassini Orbiter (Cassini-Huygens)
    aka the Cassini-Huygens Mission, was launched in 1997 to study Saturn and its rings. Its “Grand Finale” will be when it plunges into Saturn, sending back tons of information to Earth. When it loses contact with Earth, it will burn up like a meteor and become part of the planet.
  • SpaceX Falcon Heavy

    SpaceX Falcon Heavy
    Falcon Heavy is the most powerful operational rocket in the world by a factor of two. Falcon Heavy was designed from the outset to carry humans into space and restores the possibility of flying missions with crew to the Moon or Mars. Falcon Heavy missions will deliver large payloads to orbit inside a composite fairing, but the rocket can also carry the Dragon spacecraft.