Science Encyclopedia Astronomy & Space

Science Encyclopedia Astronomy & Space — page 5 — ASTRONOMY SPACE surface of Venus Robert Harrington Discovery Russians 1957 A D Sputnik the first manmade object to orbit the Earth is launched by the 1958 A D Explorer 1 is launched This was the first U S satellite to orbit the Earth 1960 A D The field of archeoastronomy expands in England 1961 A D Yuri Gagarin becomes the first man in space 1962 A D John Glenn becomes the first American man to orbit Earth 1969 A D Armstrong and Aldrin walk on the moon as part of the Apollo 11 mission 1970 A D The Russian Venera 7 becomes the first spacecraft to land softly on the 1972 A D The U S launches Pioneer 10 the first satellite destined for Jupiter 1974 A D The U S Mariner 10 probe transmits the first image of Mercury 1976 A D The U S Viking probes land on Mars 1977 A D The rings of Uranus are discovered 1978 A D Charon the moon of Pluto is discovered by James Christy and 1980 A D Voyager 1 sends back to Earth the first images of Saturn and its rings 1986 A D Voyager 2 closes in on Uranus 1986 A D The Space Shuttle Challenger breaks apart after launch 1990 A D The Hubble Space Telescope is put into orbit from space shuttle 1992 A D The Vatican under Pope John Paul II announces that the Catholic Church 1994 A D The Comet Shoemaker Levy crashes into Jupiter 1995 A D The Galileo space probe reaches Jupiter 1996 A D The Comet Hyakutake is discovered by Yuji Hyakutake 1997 A D The Mars Pathfinder lands on the Red Planet 1997 A D Cassini begins its journey to Saturn 1998 A D The Lunar Prospector reaches the moon 1998 A D Construction begins on the International Space Station 1998 A D The Galileo space probe discovers the origin of Jupiter’s Rings 1998 A D John Glenn returns to space after 36 years 1999 A D Scientists discover the real Hubble Constant 1999 A D Chandra X-ray Observatory is put into orbit Col Eileen Collins becomes 1999 A D NASA loses the Mars Climate Orbiter and the Mars Polar Lander 2000 A D The space shuttle Endeavor makes a detailed global map of Earth 2000 A D The NEAR spacecraft reaches asteroid Eros 2000 A D New evidence is found for water on Mars 2013 A D NASA’s Voyager 1 spacecraft reached interstellar space 2013 A D Physicists in Antarctica find the first evidence of cosmic rays from 2013 A D NASA’s Curiosity rover discovers signs that ancient Mars could have erred in condemning Galileo’s work that proved that the work of Copernicus was valid mainly that the planets circle the sun and not the Earth the first woman shuttle commander outside the solar system supported life in the form of primitive microbes W H A T I S A S T R O N O M Y 7

Science Encyclopedia Astronomy & Space — page 6 — 8 W H A T I S A S T R O N O M Y ASTRONOMY SPACE Claudius Ptolemaeus c 100 AD c 168 AD is known in English as Ptolemy Views of the Universe Long ago before the invention of the telescope people had a much different idea of what the universe was like The two major views of the universe through the course of history are the geocentric view and the heliocentric view The Geocentric View In 140 A D a Greek astronomer named Ptolemy wrote that the Earth was the center of the universe He thought all the stars the sun and the moon revolved around it This made sense because that is how things looked in the sky from Earth We call Ptolemy’s theory the geocentric view It is derived from geo Earth and centric center Astronomers believed the geocentric view for 1,500 years until 1543 The Heliocentric View About 500 years ago Copernicus found that the Earth and other planets revolve around the sun His theory was published in 1543 We call Copernicus’s theory the heliocentric view because helios means sun Astronomers still base their understanding of the solar system on Copernicus’s heliocentric view Nicolaus Copernicus 1473 1543 Getting to know Nicolaus Copernicus was born in 1473 in what is now Poland His father died when Copernicus was only ten His uncle a Catholic bishop raised him In 1491 he became interested in studying the skies He collected many books on astronomy and studied with famous astronomers In 1513 Copernicus built an observatory He realized that Earth and the other planets revolve around the sun This is the heliocentric view Many people did not believe him The Catholic Church banned his ideas for the next three hundred years We call Copernicus the father of modern astronomy even though Greek Indian and Muslim astronomers before him believed that the sun was the center of the solar system as well

Science Encyclopedia Astronomy & Space — page 7 — 9 W H A T I S A S T R O N O M Y ASTRONOMY SPACE We now know that our solar system is part of a bigger universe or cosmos The size of the universe is unimaginable It includes all the matter energy and space in all the galaxies How People Used the Skies People have always found the skies fascinating They found the skies helpful too They developed calendars based on the moon and sun They used the stars and midday sun to navigate The Lunar Calendar Early on people noticed that there were 291 2 days between two full moons They created a 354 day calendar Based on the phases of the moon they divided the calendar into 12 lunar months Today the Islamic calendar is still a purely lunar calendar It has twelve months based on the moon’s movements The Solar Calendar Later calendars used the movements of the sun rather than the moon The ancient Egyptians created the first 365 day solar calendar The ancient Romans made adjustments and added one extra day every four years Do you know what we call these longer years Yes they are leap years The lunar calendar is based on the phases of the moon Based on the heliocentric view the Earth revolves around the sun observatory uhb-ZUR-vuh-tor-ee a building that has telescopes and other instruments astronomers use to study the sky revolve ri-VOLV to orbit around an object theory THIHR-ee an idea that explains how or why something happens universe YOO-nuh-vurss everything that is in space including the Earth stars and planets

Science Encyclopedia Astronomy & Space — page 8 — ASTRONOMY SPACE The Gregorian Calendar Even with the improvements the calendars being used were still not quite right In 1582 Pope Gregory XIII corrected the problems He ordered that three leap years should be skipped every 400 years We use the Gregorian calendar today named for Pope Gregory It is the most widely used calendar in the world The Days of the Week You may wonder why there are seven days in a week No one seems to agree on any single reason for a seven day week But they do agree on the origins of each day’s name In English three days Saturday Sunday and Monday are named for objects in the solar system The other four days Tuesday Wednesday Thursday and Friday are named for Norse gods See the chart below Named After The Sun The Moon Tiw Norse God of war Y M O N O R T S A S I T A H W Navigation Ancient people learned to navigate by using the sun and stars Using the stars and sun people could find their north-south position when crossing deserts and seas where there were no landmarks to guide them During the day the sun’s movement in the sky guided them At night they used a star called Polaris or the North Star All stars are fixed in a set position in the sky relative to each other It is the movement of the Earth that makes the stars and the sun appear to move across the sky Originally Sun’s Day Moon’s Day Tiw’s Day Now Sunday Monday Tuesday Woden German for Odin chief Norse god Woden’s Day Wednesday Thor Norse god of thunder Frigg the Norse goddess of love Saturn 10 Thor’s Day Frigg’s Day Saturn’s Day Thursday Friday Saturday

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