How Do We Use Earth’s Motion to Determine the Length of a Day?

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# How Do We Use Earth’s Motion to Determine the Length of a Day? - PowerPoint PPT Presentation

How Do We Use Earth’s Motion to Determine the Length of a Day?. Earth’s Rotation. DO NOW:. Write the following vocabulary definitions: Rotation : The spinning motion of a celestial body on its axis. Sidereal Day:

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### How Do We Use Earth’s Motion to Determine the Length of a Day?

Earth’s Rotation

DO NOW:
• Write the following vocabulary definitions:
• Rotation:
• The spinning motion of a celestial body on its axis.
• Sidereal Day:
• The length of time it takes the Earth to complete one full rotation (360). The time is 23 hours and 56 minutes.
• Solar Day:
• The time we use to measure the length of a true day (sunrise to sunrise) although it does not represent a 360 turn.
• Zenith:
• A point in the sky directly overhead.
Using Shadows to Measure Earth’s Rotation
• Early in the day, the shadow is long and projected to the West. By mid-day the shadow is short and projected to the North, precisely at noon the shadow appears at its shortest length. At the end of day the shadow is long and projected to the East.
• There is no place on the continental United States where the Sun appears directly overhead (zenith).
• The Sun’s path is always south of the east-west line as it crosses the continental United States.
Using simple shadow stick data to determine local time and observer’s longitude