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universe all the galaxies, matter, and energy
galaxy group of billions of stars and their planets, gas, and dust
Milky Way the galaxy our solar system belongs to
solar system the sun, planets, dwarf planets, moons, asteroids, comets, and meteors
revolution the movement (orbit) around another object
rotation the spinning motion of an object on its axis
gravity the pulling force between two objects
hydrogen and helium the gases that make up the sun
nuclear fusion the process by which 2 hydrogen atoms fuse to make helium
sun spots dark areas on the sun
prominences loops of gases that link sunspots
solar flares an explosion of gases on the sun. Cause communication problems on earth
planet order Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
astronomical unit (AU) average distance of Earth to the sun is one AU
phases one of the different shapes of the moon as seen fromEarth
waxing growing larger
waning growing smaller
spring tide when the Earth, moon, and sun are allined and very high or very low tides occur
neap tide lower tides occur because the sun and moon are not alligned
geocentric the early belief that Earth was the center of the solar system and all the planets revolve around Earth
astronomer scientist who studies the solar system and beyond Earth
Ptolemy believed in geocentric theory
Aristotle believed in geocentric theory
heliocentric a theory of the solar system in which all planets revolve around the sun
comet a ball of ice and dust that orbits the sun in a long ellipse
asteroid rocky objects that revolve around the sun, too small to be planets
meteoroids chunks of rock or dust in space
meteor a meteoroid that burns up as it seems to streak across the night sky
meteorites meteoroids that hit Earth and leave craters
USSR the country the US competed with to control space in the 1950s and 1960s
Created by: sharon_eberle1