Astronomy and Earth Science Terms

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Apogee

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The point in the orbit of the moon or a satellite at which it is furthest from the earth.

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Neap Tide

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A tide just after the first or third quarters of the moon when there is least difference between high and low water.

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Solstice

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Either of the two times in the year, the summer solstice and the winter solstice, when the sun reaches its highest or lowest point in the sky at noon, marked by the longest and shortest days.

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Coriolis Effect

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An effect whereby a mass moving in a rotating system experiences a force acting perpendicular to the direction of motion and to the axis of rotation.

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Parallelism

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Earth's axis remains parallel to its previous position as Earth revolves around the Sun.

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Spring Tide

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A tide just after a new or full moon, when there is the greatest difference between high and low water.

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Equinox

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The time or date (twice each year) at which the sun crosses the celestial equator, when day and night are of equal length.

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Penumbra

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The partially shaded outer region of the shadow cast by an opaque object.

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Tides

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The alternate rising and falling of the sea, usually twice in each lunar day at a particular place, due to the attraction of the moon and sun.

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Foucault Pendulum

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A pendulum that demonstrates the rotation of the Earth by exhibiting an apparent change in its plane of oscillation.