In: Physics
Sketch position of Moon several times in a single night(can draw a horizontal sketch)
The Moon moves around the Earth in an
approximately circular orbit, going once around us in approximately
27.3 days, or one sidereal period of revolution. As it
does this its position changes, relative to the stars.
Since there are 360 degrees in a
circle, the Moon moves (on the average) 360 / 27.3 or 13.2 degrees
per day relative to the stars, which is just over half a degree per
hour, and approximately equal to its apparent size. This means that
from night to night the Moon moves a little more than one
hand-width to the East (the direction of its motion around the
Earth) relative to the stars, and from hour to hour it moves about
one diameter to the East, among the stars.
An approximate representation of the motion of the Moon around the Earth. Moving once around in 27.3 days, its average movement is about 13.2 degrees per day, or 92 degrees per week. (As is usual in such diagrams the sizes of the Earth and Moon are exagerrated, in comparison to their separation.)
The apparent motion of the Moon
from night to night.
Each night, it moves about 13 degrees, or about 26 diameters, to
the east.
The apparent motion of the Moon from hour to hour; each hour it moves about one diameter to the East.