Download Seasons

Aim: What are some celestial and terrestrial
observations?
I. Celestial Motions
A. Celestial Object – any object observed in the sky
during the day or night (ex: stars, moon, planets, sun)
1. Apparent Motion – the motion an object
appears to move, but does not actually
move in that direction or does not move at
all.
WHAT DIRECTION DO OBJECTS
APPEAR TO MOVE IN THE SKY?
From east to west. WHY?????
2. Earth rotates from west to east, causing objects in
the sky to appear to be moving from east to west.
a. Arc (part of a circle) – shape that an object
appears to make in the sky.
b. The apparent center of the arcs is Polaris (north
star) WHY?
i. Since Polaris is located above the Earth’s axis of
rotation, the stars and planets seem to rotate
counterclockwise around Polaris at approximately
15o per hour. WHY 15o per hour?
ii. The apparent daily motion of stars, moon,
and planets is due to Earth’s rotation toward
the east at a rate of 15o per hour. How long
does it take the earth to rotate 360o?
3. Solar Day – the amount of time it takes for the
earth to rotate once (24 hours). WHY 24 HOURS?
II. Terrestrial Observations
A. What are the two main motions of the earth?
That is correct!!!! Revolution (orbit) and
rotation (spin) on its axis.
1. Evidence of rotation – How do we know
that the earth rotates?
a. Coriolis Effect – observed path of an object
(or fluid) at the surface of the earth undergoing
a predictable horizontal deflection. (Rightward
deflection in the Northern Hemisphere and
leftward deflection in the Southern Hemisphere.
b. Focault Pendulum – a free swinging
pendulum. When it is allowed to swing freely,
it appears to change direction.
Focault Pendulum
B. Apparent Motion of the Sun
1. Moves from east to west _____ degrees per
hour.
a. Rises in the ___________ and sets in the
_________.
http://www.classzone.com/books/earth_science/terc/content/visuali
zations/es0408/es0408page01.cfm?chapter_no=visualization
C. SEASONS
1. Seasons are a direct result of the relative
position of the sun in the sky at different times of
the year and also due to Earth’s tilt (23.5o)
2. 1st day of Summer (Summer Solstice) June 21st
a. Longest day in Northern Hemisphere
b. 23.5o N (Tropic of Cancer)has sun directly overhead
(90o)
3. 1st day of Winter (Winter Solstice) December 21st
a. Shortest day of year in Northern Hemisphere
b. 23.5o S (Tropic of Capricorn) has sun directly
overhead
4. The Equinoxes (Autumnal Equinox and Vernal
Equinox)
September 21st and March 21st
a. 12 hours of daylight and 12 hours of
darkness
b. Sun is directly overhead at the equator