1. Agenda – Thursday, Feb 20
Last chance to hand in the Earth’s Motion Book Questions that were collected yesterday at end of hour. If you now have them complete, turn them into me.
Today’s Topic: Earth’s Rotation
(Sidereal vs Synodic)
Then we will continue with Revolution details

2. Period of Earth’s Rotation?
About 24 hours
but the exact period depends on how you define it.

3. Sidereal Rotation With respect to a distant (infinitely far away) star
Period of Sidereal is a constant value of hours, 56 min, sec
Does not vary throughout year

4. Synodic Rotation With respect to the sun
The period varies throughout the year
Period averages 24 hours
Synodic measurements are based on the position of the sun compared to earth

5. So what does the difference mean?
Distant stars rise every 23 h 56 m 4 s
So…
Stars rise 4 minutes earlier every night
When would Earth’s synodic period be longest?
When would earth’s synodic period be shortest?