Q:

Why does the sun move across the sky?

A:

Quick Answer

The sun appears to move across the Earth's sky as a consequence of the Earth's rotation. As Earth turns on its axis, an observer on the surface sees the sun appear to come up somewhere over the eastern horizon, rise to a peak around midday and then begin its descent toward the west. This cycle varies slightly from one latitude to another, as well as from one day to another.

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Full Answer

Earth spins once on its axis every 24 hours. To a stationary observer at most locations on the surface of the Earth, this motion imparts the appearance of motion to the sun. The exact spot on the local horizon where the sun appears to rise is dependent on where on the Earth the observer is located and what time of year it is.

In addition to spinning on its axis, the Earth inclines at about 23 degrees. This tilt brings first one and then another hemisphere into position to point more directly toward the sun. For observers in tropical latitudes, this motion causes the sun to cross the sky higher and higher throughout the spring until the summer solstice, when it begins moving back down toward the horizon. To an observer near the pole, the sun rises above the horizon only from late spring to early fall. It appears to circle the horizon during this time and disappears entirely through the winter months.

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Related Questions

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    What changes happen in the sun's position in the sky over the course of a year?

    A:

    The sun's path through the sky moves farther north as the calendar year progresses from January to June before going south for six months. In late March and late September, the sun follows the celestial equator. After the vernal equinox of March, residents of the northern hemisphere notice the sun gradually moving northward until the summer solstice. The sun then moves southward until the winter solstice.

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  • Q:

    How many degrees does the sun move each day?

    A:

    The sun appears to move in the sky just under one degree a day. It moves a full rotation, 360 degrees, in 365.2422 days. To the naked eye, it appears to move eastward over the course of a year with respect to its position in comparison to the stars.

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    Why do shadows change length during the day?

    A:

    Shadows change length throughout the day because the angle at which the sun shines on stationary objects changes with the Earth’s rotation. For example, early in the morning, when the sun is near the horizon, it casts long shadows when an object blocks the light. Conversely, when the sun is high overhead during the middle of the day, the shadows become shorter, as the angle of the sun has changed.

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    Why do we have day and night on earth?

    A:

    Day and night on Earth are caused by the planet's rotation around its axis and its position relative to the Sun. The Earth rotates from west to east, so places further east experience daybreak and nightfall sooner. One hemisphere of Earth is in daylight at any given time.

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