Section C - Earth Sun Geometry and The Seasons

What is the Shape of the earth?

• oblate spheroid: near-perfect sphere

  • bulge at the equator, circumference is 40,075 km

  • flattened at the poles, c is 40,008 km

Curvature influences angle of incidence by what?

latitude

Low latitudes have a _ angle of incidence

higher

High latitudes have _ angle of incidence

lower

Subsolar point (2)

• sun is directly overhead

• 90 degree angle

Plane of the ecliptic

an imaginary plane that passes through the sun and every point of earth’s orbit

What is the direction of earth’s rotation around the sun?

counterclockwise

How long is one full revolution?

365.24 days

How long is one rotation?

24 hours

Define types of elliptical path (2)

• perihelion: closest point in orbit, about 3.3%

  • January 4

• aphelion: farthest point in orbit

  • July 6

True or False: seasons are caused by the distance from the sun

False

What are seasons caused by? (3)

1. rotation (counterclockwise)

2. revolution (counterclockwise)

3. tilt/ inclination

Earth’s tilt is known as:

polarity or parallelism

How much is the axis tilted from the perpendicular to the plane of eclipta?

23.5 degrees

The earth’s axis points towards what?

the north start (polaris)

The subsolar point migrates throughout the year between which two latitudes?

• the Tropic of Cancer and the Tropic of Capricorn

The date of June Solstice

June 21

What happens during the June Solstice?

• North Pole is oriented most directly toward the sun

• rays of sun at noon strike perpendicular to the surface of the Tropic of Cancer

  • subsolar point

• arctic circle: all points north of 66.5 degrees N latitude experience 24 hours of light on this day (all points within 23.5 degrees of the North Pole)

All latitudes are bisected evenly by the circle of what?

illumination

The date of December solstice

December 21

December Solstice (3)

• rays of the sun at noon strike perpendicular to the surface of the Tropic of Capricorn

• day lengths are longer in the southern hemisphere

  • day length is equal at the equator

• antarctic circle: all points south of the parallel of 66.5 degrees S latitude experience 24 hours of the light

During September and March Equinox, how many hours of day and night are all latitudes experiencing?

• 12 hours day, 12 hours night

About 24 time zones

• each zone covers 15 degrees of longitude

  • takes earth 1 hour to rotate that distance

• 24 hours for a full rotation of 360 degrees

  • 360 degrees/ 24 hr = 15 degrees/ 1hr

Which city is set standard 0 degrees for time zone system

Greenwich, England

What is solar noon?

the time of day when the sun reaches its highest point above the horizon

Canadian time zones (6)

• pacific standard time

• mountain standard time

• central standard time

• eastern standard time

• newfoundland standard time

• atlantic standard time

Which province does not observe daylight savings?

Saskatchewan

Lloyd Minister in AB is on which standard time?

Mountain

Newfoundland and Labrador use how many min difference from Atlantic?

30

180 degrees _ marks the start and end of each calender day

Meridian

What does ‘AM‘ stand for?

ante meridian before noon

What does ‘PM’ stand for?

post meridian; afternoon