Term | Definition |
astronomy | the study of the moon, stars, and other objects in space |
axis | an imaginary line that passes through Earth's center and the North and South poles, about which Earth rotates |
rotation | a complete turn around a central point |
revolution | the movement of an object around another object |
orbit | the path of an object as it revolves around another object in space |
solstice | the two days of the year on which the sun reaches its greatest distance north or south of the equator |
equinox | the two days of the year on which neither hemisphere is tilted toward or away from the sun |
gravity | the attractive force between objects |
gravitational force | the force of gravity |
atmosphere | a mass of gases that surround a planet or star |
craters | a large round pit caused by the impact of a meteoroid |
phases | one of the different apparent shapes of the moon as seen from Earth |
solar eclipse | the blocking of sunlight to Earth that occurs when the moon is directly between the sun and Earth |
lunar eclipse | the blocking of sunlight to the moon that occurs when Earth is directly between the sun and the moon |
neap tide | the tide with the least difference between consecutive low and high tides |
spring tide | the tide with the greatest difference between consecutive low and high tides |
umbra | the darkest part of a shadow |
penumbra | the part of a shadow surrounding the darkest part |
geocentric | a model of the universe in which Earth is at the center of the revolving planets and stars |
heliocentric | a model of the solar system in which Earth and the other planets revolve around the sun |
ellipse | an oval shape, which may be elongated or nearly circular |
core | the central region of the sun, where nuclear fusion takes place |
velocity | speed in a given direction |
satellite | an object that revolves around another object in space |
space probe | a spacecraft that has various scientific instruments that can collect data, including visual images, but has no human crew |
space shuttle | a spacecraft that can carry a crew into space, return to Earth, and then be reused for the same purpose |
space exploration | exploring space |
rover | a small robotic space probe that can move about the surface of a planet or moon |
remote sensing | the collection of information about Earth and other objects in space using satellites or probes |
vacuum | a place that is empty of all matter |
microgravity | the condition of experiencing weightlessness in orbit |