ASTRONOMY TIMELINE

THALES OF MILETUS

• Birth and Death:624 BCE – c. 546 BCE
• Not much of his work is known since none of it survived. However, we know that he was a highly respected man in Greece that was the only philosopher before Socrates to be among the seven stages. He has been reported to predicting a solar eclipse, which was an impressive feat since no one knew how the Sun, Earth and Moon orbited during a sold eclipse.

PYTHAGORAS

• Birth and Death: 570 BC, Sames, Greece- 475 BC, Metapontum
• Him and his inner circle of friends believed that souls would moved to animals after death and that it would be cannibalism to eat them. However, that didn't seem to bother most since they ate animals anyways. He realized the orbit of the moon was inclined to earths equator, and deduced that the evening star was the same as the morning star. His worked influenced Ptolemy and Johannes.

PHILOLAUS

• Birth and Death: 470 BC - 385
• The Earth revolves around a central fire along with the other heavenly bodies, including a planet called the counter earth which orbits below the earth. This was suppose to explain some of the lunar eclipses, but was criticized for not working with his system.

PLATO

• Birth and Death: 428/427 B.C. Athens, Greece - 348/347 BC Athens Greece
• He believed that all substances were composed of air, earth, fire and water. He believed in a spherical earth which was the center of the universe and a motion of planets along crystalline spheres. He founded his own academy in Athens, which Aristotle joined at around the age of 18

EUDOXUS OF CNIDUS

• Birth and Death: 400 - 390 BC
• In two of his works, he described constellations schematically the phases of fixed stars (the dates when they are visible), and the weather associated with different phases. He also discussed the sizes of the Sun, Moon and Earth. He made a geometric model of the motions of the sun, the moon, and the five planets known in antiquity

ARISTOTLE

• Birth and Death: 384 BC Stagria, Greece - 322 BC, Chalois
• Proved that the earth is spherical, and believed that is was at the center of the universe. He knew that if the Earth revolved around the sun, then we should see the stars shift positions throughout the year. Since he didn't have the technology to detect this shift, he was lead to believe that Earth rests at the center while the stars and planets all revolve around it

ERATOSTHENES

• Birth and Death: 276 BC Cyrene, Libya - 194 BC Alexandria, Egypt
• He measured the altitude of the noontime sun at Alexandria at its maximum on June 21st. On that date, the sun is directly overhead at noontime at Syene, in Southern Egypt. He knew how far it was from Alexandria to Syene, so he used geometry and the difference in zenith angle to estimate the size of the Earth. He also measured the tilt of the Earth axis by 23.5 degrees, which gives us seasons

ARISTARCHUS

• Birth and Death: Samos, Greece - 230 BC, Alexandria, Greece
• Was the first to actually put forward the idea that the sun was in the center of the universe and that the Earth revolved around it. His theory, however, was considered way to radical. He also attempted to measure the relative distances between the Earth and the Sun and the Earth and the Moon. Even if his method was reasonable, it wasn't very accurate because he lacked the correct technology

HIPPARCHUS

• Birth and Death: 190 BC Iznik, Turkey - 120 BC Rhodes Greece
• Is widely considered to be the greatest astronomer of ancient times. He compiled the first known star catalogue to organize astronomical objects, and also came up with a scale to define the brightness of stars. A version of this magnitude is still used today. He measured the distance from the Earth to the Moon to be 29.5 Earth diameters (we know now that it's 30). Perhaps his greatest achievement was discovering the precession, or wobble, of Earths axis, which is caused by the gravitational pull of the sun and moon.

CLAUDIUS PTOLEMAEUS (PTOLEMY)

• Birth and Death: 90 AD Alexandria, Egypt - 168 AD, Alexandria, Egypt
• He developed a model that predicted the movements of the sun, Earth, Moon, planets and stars. His model, called Ptolemaic system, visualized an Earth-centered universe and assumed that all Astronomical objects move at constant speeds in circular orbits

NICOLAS COPERNICUS

• Birth and Death: February 19, 1473, Toruń, Poland - May 24, 1543, Frombork, Poland
• Began a new era of astronomy when he concluded that the sun was the center of the universe. He revised the Ptolemaic system, but kept the orbits circular. The revolutionary idea was not popular with the church, but several other astronomers such as Galileo helped eventually prove that this model of the universe more accurately portrayed reality

TYCHO BRAHE

• Birth and Death: December 14, 1545, Sualoü Municipality, Sweden - October 24, 1601, Prague, Czech Republic
• Built on observatory from which he made the most accurate astronomical observations of his time. His observatory contained sophisticated equipment for mapping the stars positions, and for more than 20 years he made detailed records of his findings. He believed that the universe was a blend of the Ptolemaic and Copernican models, and created his own model in which the planets orbits the sun and the sun orbits the Earth.

GALILEO GALILEE Is the father of observational astronomy.

• Birth and Death: February 15, 1564, Pisa Italy - January 8, 1642, Arcetri
• He created his own telescope after hearing about the Dutch invention. Although it wasn't that powerful, he still made stunning discoveries. He saw the craters, mountains, and valleys of the Moon, he noticed the huge amount of stars in the Milky Way, kept precise records of sunspot activity and the phases of Venus, and discovered four moons orbiting Jupiter. These moons are still called the Galilean Moons today. During the time where the Earth was still considered to be the center, he publicized the fact that other astronomical objects were clearly revolving around something other than Earth. He was put under house arrest for the rest of his life for his views.

JOHANNES KEPLER Was Tycho Brahe's assistant and student.

• Birth and Death: December 27, 1571, Weilder Stadt, Germany - November 15, 1630, Regensburg, Germany
• He inherited his teachers collection of astronomical records and used them to develop three laws of planetary motion. He believed in the Copernican model, but found it difficult to put in mars with a circular orbit. He then used the idea of elliptical orbits to describe the motions of the planets, which became Kepler's first law. His second law states that a line from the sun to a planet sweeps out equal areas in equal amounts of time. The third law is the square of the number of years a planets orbital period in equal to the cube of that planet's average distance from the sun.

ISAAC NEWTON

• January 4, 1643,Woolsthorpe -by-Culsterworth, UK -March 31, 1727
• His theory of universal gravitation was the foundation of Kepler's laws of planetary motion, but also went farther: Newton showed that the laws governing astronomical bodies were the same laws governing motion on the surface of the Earth. Newton's scientific ideas are so complete that they still offer an accurate description of physics today

MARIA MITCHELL

• Birth and Death: August 1, 1818, Nantucket, MA - June 28, 1889, Lynn, MA
• She discovered a comet through a telescope, for which she was awarded a gold medal by the king of Denmark. She was then thrust into the international spotlight and became America's first professional female astronomer. At the age of 12, she helped her father position her house by observing a solar eclipse. She also became a professor of astronomy at the newly-founded Vassar College

HENRIETTA SWAN LEAVITT

• Birth and Death: July 4, 1868, Lancaster, MA - December 12, 1921, Cambridge, MA
• Was a member of 'Pickering Women'. She discovered that a particular type of variable star known as a cepheid could be used as a distance maker, making it possible to determine astronomical distances to objects.

ALBERT EINSTEIN

• Birth and Death: March 14, 1879, Ulm, Germany - April 18, 1955, Princeton, NJ
• His theory of relativity extended Newtonian mechanics to very large speeds close to the speed of light. It describes the changes in measurements of physical phenomena when viewed by observers who are in motion relative to the phenomena. Einstein this further in the general theory of relativity, which includes the effects of gravitation. According to his theory, mass and energy determine the geometry of space time, and curvatures of space time manifest themselves in gravitational forces

EDWIN HUBBLE

• Birth and Death: November 20, 1889, Marshfield, MO - September 28, 1953, San Marino, CA
• Made an incredible contribution to astronomy and cosmology when he discovered that faraway galaxies are moving away from us. Known as Hubble's law, the theory states that galaxies recede from each other. This concept is a cornerstone of the Big Bang model of the universe