(Encyclopedia)
CE5
A. Nimbus weather satellite
B. Syncom communications satellite
satellite, artificial, object constructed by humans and placed in orbit around the earth or other celestial body…
(Encyclopedia) ephemeris time (ET), astronomical time defined by the orbital motions of the earth, moon, and planets. The earth does not rotate with uniform speed, so the solar day is an imprecise…
(Encyclopedia) escape velocity, the velocity a body must be given in order to escape the gravitational hold of some other larger body, e.g., the earth, moon, or sun. A body given less than the escape…
(Encyclopedia) airglow, faint diffuse illumination of the sky originating in the upper atmosphere. Although it occurs at all times of day throughout the upper atmosphere, it is most typically visible…
A belt of asteroids (fragments of rock and iron) between Mars and Jupiter separate the four inner planets from the five outer planets. Jupiter, the largest planet in our solar system, was named…
Venus is often called Earth's twin because the two planets are close in size, but that's the only similarity. The thick clouds that cover Venus create a greenhouse effect that keeps it sizzling at…
(Encyclopedia) mantle, portion of the earth's interior lying beneath the crust and above the core. No direct observation of the mantle, or its upper boundary, has been made; its boundaries have been…
(Encyclopedia) day, period of time for the earth to rotate once on its axis. The ordinary day, or solar day, is measured relative to the sun, being the time between successive passages of the sun…
Earth's Moon is a small ball of gray rock revolving 239,000 miles around Earth. It is just one of many in the solar system. The Moon has no air and no water. It is about one-fourth as large as…
