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384 BCE
Aristotle
(384-322) Aristotle was the first to classify human knowledge into subjects such as math and biology. He invented the idea of formal logic and his writings still remain as a current in philosophical debate. He knew the earth was spherical and believed it was geocentric. -
100
Ptolemy
(100-168) Ptolemy's most important work was the Algamest, which contains his theory of movement of the sun, moon, and planets. He described the universe based on an earth-centered system, and used models to predict the positions of the sun, moon, and planets. In 13 books, he describes his theory of the universe. -
1473
Copernicus
(1473-1543) Copernicus proposed the idea the the planets revolved around the sun instead of them revolving around Earth. He wrote a book to give out to his friends containing his view of the universe. In it, he states that the earth's rotation is also responsible for the rise and setting of the sun, ans the movement of the stars. He finally published the book in 1543, shortly before he died. -
1546
Tycho Brahe
(1546-1601) Tycho worked in developing and creating instruments and fixing and measuring stars. The observations he made were the most reliable possible before the telescope. This included studying the solar system and positions of over 770 fixed stars. He studied a supernova in 1572. He made a theory that the sun and moon were orbiting around Earth. -
1564
Galileo
(1564-1642) Galileo invented an improved telescope that allowed him to observe many planets. He supported a sun-centered solar system. Galileo discovered that Venus had phases, much like the moon. This proved that it rotated around the sun. He also developed his theory of motion and falling objects, and the law of acceleration. -
1570
Hans Lippershey
(1570-1619) Many believe that Hans Lippershey invented the first telescope and possible an early microscope. However, he was the first person to apply for a patent of the telescope. His first device was two lenses secured so it could be looked through. This led to the invention of a spyglass and other magnification lenses. -
1571
Johannes Kepler
(1571-1630) Johannes Kepler discovered the three major laws of planetary motion. The observations he made were turned into a dynamic universe system, where the sun pushes the planets into non circular orbit. -
Difference between refracting and reflecting telescopes
A refracting telescope focuses on light, making far objects visible and clear. Most have two lenses, one smaller and one larger. Reflecting telescopes use curved mirrors that can reflect light to make an image. It is designed this way so it can easily be looked through. -
Giovanni Cassini
(1625-1712) Giovanni Cassini created the first estimate of the dimensions of the solar system when he found the distance of Mars from Earth. He also determined the first successful measurements of longitude, which allowed land itself to be measured. In 1675, he discovered the rings of Saturn, and around 1690, he was the first to see the rotation in Jupiter's atmosphere. -
Sir Isaac Newton
(1643-1724) Sir Isaac Newton made the Three Laws of Motion, from his description of gravity and Johannes Kepler's Laws of Planetary Motion. Isaac Newton is most famous for his work in gravity. He invented reflecting lenses for telescopes, and discovered calculus, which led to more ways of solving mathematical problems. -
William Herschel
(1738-1822) William Herschel discovered Uranus and its two moons. He built his own telescope and eyepieces magnified so that during his observations, he was able to see the orthodox object. -
Percival Lowell
(1855-1916) Percival Lowell believed there were canals on Mars, meaning there was a Martian civilization. In the Lowell Observatory, there was the discovery of the rotation of spiral galaxies and a hint to an expanding universe. His search for a ninth planet resulted in the discovery of Pluto. -
Ejnar Hertzsprung
(1873-1967) Hertzsprung classified stars by comparing their color to their brightness. In 1913 he created the luminosity scale of Cepheid variable stars. The Hertzsprung-Russell diagram shows stellar types and brightness. -
Albert Einstein
(1879-1955) Albert Einstein is best known for his Theory of Relativity, and his famous equation of mass-energy equivalence. He also discovered the law of the photoelectric effect and made contributions to the quantum theory. -
Edwin Hubble
(1889-1953) Hubble discovered that the universe is expanding and that it is larger than the Milky Way alone. He classified galaxies into categories based on their appearance. -
Karl Jansky
(1905-1950) Karl Jansky discovered three different types of static, one being the radio waves coming from the Milky Way. This led to the development of radio astronomy. -
John Glenn
(1921-2016) John Glenn was the first American to orbit in space, and he orbited longer than Yuri Gagarin. -
Neil Armstrong
(1930-2012) Neil Armstrong was the first person to land on the moon, and walk on it. -
Yuri Gagarin
Yuri Gagarin was the first person to orbit the earth in space. He circled for a little over one orbit. This was a challenge to America because he was Russian. -
Sputnik
Sputnik was the first satellite to orbit Earth on its elliptical path. This led to new developments in politics, military, technology, and science and started the space race. -
The Apollo Program
(1963-1972) Their goal was to see how many times astronauts could make it to the moon and back safely. -
First Space Shuttle Flight
The shuttle program was called the Space Transportation System. -
Mars Pathfinder Expedition
It was designed as a way to deliver the first robotic rover to Mars. -
Cassini Orbiter
It reached Saturn and its moons giving data the changed our understanding of the planet.
