1. EIS 2.2 Scaling of the Sun, Earth, Moon System

2. Table 1 Size & Distance Comparison of the SEM
Solar System Body
Distance from Earth (km)
Earths
Away
Diameter
(km)
Across
Sun
150,000,000
~ 12,000
1,392,000
109
Moon
384,000 30
3,500
0.27
Earth
Equator =
12,756 1

3. 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.

4. 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

5. 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

6. 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.

7. 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 days. In the Gregorian calendar, the calendar used by most modern countries, the following three criteria determine which years will be leap years:

8. 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 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.

9. 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!