EIS 2.2 Scaling of the Sun,
Earth, Moon System
Table 1 Size & Distance
Comparison of the SEM
Distance from
Earth
(km)
Earths
Away
Diameter
(km)
Earths
Across
150,000,000
~ 12,000
1,392,000
109
Moon
384,000
30
3,500
0.27
Earth
-------------
-------------
Equator =
12,756
1
Solar System
Body
Sun
I. Moon
1.
2.
3.
4.
5.
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
Since it rotates at the same rate it
revolves around Earth, we only see one
side of the Moon – EVER.
II. Day
1. Caused by Earth rotating on its axis once
every 24 hours (about – takes slightly
longer)
III. Month
1.
Sidereal Month: The time it takes Moon to
revolve around Earth & be next to same
background star.

2.
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
1.
2.
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)
1.
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)
i.
ii.
iii.
iv.
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
1.
2.
3.
4.
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! ~ 200 million years to go around
once!
It is 400 times larger than Moon & 400
times farther away, so Sun & Moon
appear same size in sky.
1 million Earth’s would fit inside Sun.