Around & Around Again

ROTATING or REVOLVING?

What Makes Day and Night

KEY TERMS

Rotation: The Earth's spinning about its internal axis at a tilt.


Axis: An imaginary straight line that passes through the center of the Earth as well as its poles.


Revolution: The Earth's orbital movement around the Sun.

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Day vs. Night

The Earth rotates from west to east causing the Sun to rise on the east and set on the west. The rotation also causes day and night. One complete rotation occurs every 24 hours, which is a full day. The side of Earth that is facing the sun experiences daytime while the other side experiences nighttime. However, the Earth is not the only one that rotates; the moon also rotates as it revolves around the Earth.

The Reasons for Seasons

The Earth's axis tilts at an angle of 23.5 degrees and for this reason, the Earth experiences seasons during its revolution around the sun. However, since there is a tilt, the bottom half of the Earth and the top half of the Earth do not have the same seasons at the same time. One half is always leaning towards the sun while the other half leans away from the sun. For example, when the Northern Hemisphere is leaning towards the sun, summer is occurring; when the Southern Hemisphere is leaning away from the sun, winter is occurring. Lastly, one revolution takes 365 days, or one year. The moon also revolves around the Earth, but it only does so once every month.
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Bill Nye explains Seasons

SOL 4.7

The student will investigate and understand the relationships among the Earth, moon, and sun. Key concepts include

a) the motions of the Earth, moon, and sun (revolution and rotation);

b) the causes for the Earth's seasons and phases of the moon;