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EIS 2.2 Scaling of the Sun, Earth, Moon System. Table 1 Size & Distance Comparison of the SEM. I. Moon. Age ~ 4.3-4.5 billion years old, a bit younger than Earth When a Mars-sized rock hit Earth, debris traveled at just the right speed to stay in orbit around Earth to create the Moon.
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I.Moon • Age ~ 4.3-4.5 billion years old, a bit younger than Earth • When a Mars-sized rock hit Earth, debris traveled at just the right speed to stay in orbit around Earth to create the Moon. • Has no atmosphere, so no weather. • Diameter ~ ¼ of Earth’s diameter • We only see one side of the Moon – EVER. It rotates at the same rate it revolves around Earth.
II. Day • Caused by Earth rotating on its axis once every 24 hours (about –slightly shorter) • Sun appears to rise in the east & set in the west b/c Earth rotates counter-clockwise. EAST WEST http://www.learner.org/jnorth/tm/ReasonsBack.html
III. Month • Sidereal Month: The time it takes Moon to revolve once around Earth with respect to the background stars. • 27.3 days to go from Point A back to Point A • Synodic Month: The time it takes Moon to revolve around Earth and be in the same phase. (it’s longer b/c Earth is moving-so Moon is playing catch up to get to the same phase) • 29.5 days to go from, say, full Moon to full Moon http://www.sumanasinc.com/webcontent/animations/content/sidereal.html
IV. Year • Caused by Earth taking ~ 365 ¼ days to revolve around the Sun. • We don’t add 6 hours to the clock every year. Instead we add a whole day, February 29th, every 4 years.
IV. Year (don’t need to copy) • Some exceptions to this rule are required since the duration of a solar year is slightly less than 365.25 days. In the Gregorian calendar, the calendar used by most modern countries, the following three criteria determine which years will be leap years:
IV. Year (don’t need to copy) • Every year that is divisible by four is a leap year • Of those years, if it can be divided by 100, it is NOT a leap year, UNLESS • The year is divisible by 400. Then it IS a leap year. • So, years 1800, 1900, 2100, 2200, 2300, and 2500 are NOT leap years, while 1600 & 2000 ARE leap years. http://www.timeanddate.com/date/leapyear.html
V. The Sun • It is 400 times wider than Moon & 400 times farther away, so Sun & Moon appear same size in sky. • 1 million Earths would fit inside Sun. • 109 Earths fit across Sun’s diameter. Don’t need to copy the below info • It is one of 200 billion stars in the Milky Way galaxy • It (& our solar system) revolves around center of galaxy at ½ a million miles per hour! That’s ~ 200 million years to go around once!