Do Not Write What is in Yellow

APPARENT MOTIONS OF THE CELESTIAL OBJECTS

Definitions

Celestial sphere: Imaginary sphere encircling Earth on which all object in the night sky appear

Celestial object: Object in the sky outside Earth’s atmosphere; the sun, moon, stars, planets

Terrestrial: Objects that are a part of Earth, such as rocks, oceans, and clouds

MotionsThe sun, moon, planets, stars or any distant object

seems to rise in the east and set in the west- this is an illusion: the Earth is the object that is moving

The apparent motion of objects occurs at a rate of 15 degree per hour, which is the rate that earth rotates

Daily Motion: the movement of a celestial object over a 24-hour period

Day: Average interval of time during which the sun passes from its highest point on one day to its highest point on the next; ~24 hours

Zenith: The point on the celestial sphere that is directly above the observer.

From Different PerspectivesMid-Latitudes: Stars appear to move from

east to west in circular pathsNorth Pole: Stars appear to move in a

circle

STAR'S PATH THROUGH THE SKY

The Earth rotates, causing the stars to appear to rise and set. Remember that the Sun is a star. It rotates/spins in place but does not revolve/orbit

InformationSundials were used to tell time using the

apparent movement of the sunThe passing of hours is indicated by the

movement of the shadowDays are short during the winter because

we are pointed away from the sunso the sun is below the horizonmost of the daySundialsMore on sundials

Path of the Planets

Planets do not remain in fixed positions among the stars

Planets change their position from night to night

Each planet has its own unique motion

Sometimes they appear to drift west, other times east

“Planet” = Wanderer

The Moon

The moon revolves around Earth in about 27 days

The moon rises about 50 minutes later each evening

The path of the moon varies from higher to lower depending on the time of year

The moon’s path is similar to the sun’s as it looks like it rises and sets

Apparent Motions of the SunThe sun appears to rise in the east, travel in

an arc across the sky and set in the westThe greater the length of the sun’s path

over an area, the more hours of daylightIn the spring and fall, the sun rises due

(exactly) east and sets due westIn the summer, the sun rises north of east

and sets north of westIn the winter, the sun rises south of east

and sets south of west

Changes in the Altitude of the Sun at Noon

The sun is always highest at local solar noon

Only between the latitudes of 23.5 degrees North and 23.5 degrees South can the noon sun be directly overhead