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100
384-322 BC Aristotole
Aristotle was a Geek philosopher who thought Earth was the center of all things. His geocentric model of the solar system placed the moon, sun, planets and stars on a series of circles that surrounded the Earth. -
Period: 100 to 170
Ptolemy
Ptolemy was an astronomer, geographer, and mathemetician who lived in Alexandria, Egypt. He developed a geocentric model of the solar system that was used for the next 14 centuries. In Ptolemy's model, the planets moved on asmall circles that in turn moved on larger circles. It allowed prediction of the motion of planets years into the future. -
Period: 100 to Jan 1, 1550
Geocnetric Models Dominate
The earliest models for the solar system assumed that the Earth was the center of the soalr system with the sun, moon, and planets circling it. -
Period: Feb 19, 1473 to May 24, 1543
Copernicus
Copernicus was a Polish astronomer who developed the first detailed helicentric model of the solar system. His model used a wheels-on-wheels system like Ptolemy's, but Copernicus's model fit observations better than the geocentric model of Ptolemy. -
Period: Jan 3, 1550 to
Heliocentric Models Dominate
Our current model of the solar system is the sun-centered or heliocentric model, where all of the bodies in he solar system orbit the sun. -
Period: Feb 15, 1564 to
Galileo
Galileo was a scientist who approached questions using the scientific method. He made significant improvements to the telescope and used it to veiw celestial objects. HIs observations gave support to the heliocentric model of the solar system. -
First Rocket Launch
robert Goddard launches the world's first liquid-fueled rocket, which he also built. -
Sputnik 1
The world's first artificial satellite, the Sputnik 1, was launched by the Soviet Union in 1957. Since then, thousands of satellites from more than 40 countries have been deployed. -
Period: to
Artificial Satellites
An artificial satellite is any human-made object placed inorbit around a body in space. Today, artificial satallites orbit Earth and send data about our lant back to ground stations. -
Luna 2
Luna 2, a Soviet Space craft, is the first reach the Lunar Surface. -
Period: to
Missions to the Moon
Missions to the Moon have been conducted by the Soviet Union, United States, European Space Agency, Japan, India and the People's Republic of China. Between 1968 and 1972, manned missions to the Moon were conducted by the United States as part of the Apollo program. -
Period: to
Mars Robotic Explorers
The Mars exploration Rovers Spirit and Opportunity landed on Mars in January 2004. They were designed to explore Mars for 90 days, but the Spirit rover lasted until 2010. -
Vostok 1
Soviet cosmonaut Yuri Gagarin was the first human to cross into outer space. -
First Man on the Moon
Apollo 11 was the spaceflight that landed the first humans on the Moon, Americans Neil Armstrong and Buzz Aldrin. Armstrong became the first to step onto the lunar surface, and he and Aldrin spent about two and a half hours outside the spacecraft. -
Salyut 1
Salyut 1 was was the first space station of any kind. Its second crew launched in Soyuz 11 and remained on board for 23 days. -
Period: to
Outer Planet Exploration
Outer Planet exploratin began when the Pioneer 10 became the first spacecraft to visit any planet beyond the asteroid belt, passing Jupiter on December 3, 1973. The most recent outer planet discovery was in 2005 when the second part of the Cassini mission (Saturn) parachuted the Huygens probeto a soft landing on Titan. -
Curiosity Rover
In December 2012, Curiosity 's two-year mission was extended indefinitely.
