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Earth, Moon, Sun
Term | Definition |
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Astronomy | the branch of science that deals with celestial objects, space, and the physical universe as a whole. |
Axis | an imaginary line about which a body rotates. |
Rotation | the action of rotating around an axis or center. |
Revolution | an instance of revolving. |
Orbit | the curved path of a celestial object or spacecraft around a star, planet, or moon, especially a periodic elliptical revolution. |
Solstice | when the sun reaches its highest or lowest point in the sky at noon, marked by the longest and shortest days. |
Equinox | when day and night are of equal length |
Gravity | the force that attracts a body toward the center of the earth, or toward any other physical body having mass. For most purposes Newton's laws of gravity apply, with minor modifications to take the general theory of relativity into account. |
Law of universal gravitation | particle attracts every other particle in the universe using a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres. |
Mass | a coherent, typically large body of matter with no definite shape. |
Weight | a body's relative mass or the quantity of matter contained by it, giving rise to a downward force; the heaviness of a person or thing. |
Inertia | a property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force. |
Newton’s First Law of Motion | object at rest will stay at rest and an object in motion will stay in motion with the same speed and direction unless acted upon by unbalanced force. |
Phase | a distinct period or stage in a process of change or forming part of something's development. |
Eclipse | an obscuring of the light from one celestial body by the passage of another between it and the observer or between it and its source of illumination. |
Solar Eclipse | an eclipse in which the sun is obscured by the moon. |
Umbra | the fully shaded inner region of a shadow cast by an opaque object, especially the area on the earth or moon experiencing the total phase of an eclipse. |
Penumbra | the less dark outer part of a sunspot, surrounding the dark core. |
Lunar eclipse | an eclipse in which the moon appears darkened as it passes into the earth's shadow. |