Chapter 3: Earth-Sun Relationships and Solar Energy

Physical Physical GeographyGeographyNinth EditionNinth Edition

Robert E. Gabler

James. F. Petersen

L. Michael Trapasso

Dorothy Sack

3.1 Solar System and Beyond

• Galaxy: enormous cluster of stars, dust, and gases.– Our sun is one of billions of

stars within the Milky way Galaxy

– Vast distances• Other than the sun, our

nearest star is 4.2 light years away

3.1 Solar System and Beyond

• Solar System• Gravity: attractive force one

body has on another• Mass: the greater the mass, the

greater the gravitational pull.• Planet: celestial body in orbit of

the sun, with sufficient gravitational attraction to overcome rigid forces and remain nearly spherical.

3.1 Solar System and Beyond

• Our solar system– Satellites (earth’s moons)– Numerous asteroids– Comet: head (collection of

solid fragments held together by ice)

– Meteors: small stonelike, or metallic bodies.

– Meteorite: meteor that survives the fall through our sky.

3.1 Solar System and Beyond

• The Planets– Terrestrial: 4 closest to the sun

• Mercury, Venus, Earth, and Mars• Solid surfaces

– Gas Planets: 4 furthest from sun• Jupiter, Saturn, Uranus, and Neptune• Huge balls of gas and liquid

Comparison of the Planets

3.2 The Earth-Sun System

• Sun and its Energy– Thermonuclear fusion

powers the sun– 2 hydrogen atoms fuse

together to form 1 helium atom.

– Photosphere– Chromosphere– Corona

3.2 The Earth-Sun System

• Solar wind: directed toward the magnetic poles.

• This forms an aurora– Northern lights (Aurora

Borealis)– Southern lights (Aurora

Australis)

Aurora Borealis

3.2 The Earth-Sun System

• Sunspots: intensity of solar winds

• Next cycle should peak around the year 2012.

3.2 The Earth-Sun System

• Solar Energy and Atmospheric Dynamics– energy emitted from the

sun is in the form of Electromagnetic energy.

– Shortwave (SW) radiation– Longwave (LW) radiation:

energy that may have been emitted from earth.

– Solar constant

3.2 The Earth-Sun System

• Movements of Earth– Galactic movement– Rotation– revolution

3.2 The Earth-Sun System

• Rotation– Earth turns eastward – Counterclockwise spin

on its axis– 24 hours per rotation– Speed is fastest at the

equator.

Circle of Illumination

3.2 The Earth-Sun System

• Revolution– Slightly elliptical orbit– Closest to sun near Jan.

3rd (perihelion)– Furthest from sun

around July 4th (aphelion)

– This has minimal affect on the energy receipt on earth

3.2 The Earth-Sun System

• Plane of the ecliptic– Earth is titled at 23.5

degrees. – angle of inclination

• Parallelism: Earth’s axis remains parallel to its former position.

• These positions change slowly over time (Milankovitch cycles)

3.3 Sun Angle, Duration, and Insolation

• Insolation: Solar radiation received by Earth.– Main source of energy on

our planet– Seasonal variations in

temperature due primarily to fluctuations in insolation

– Direct rays– Oblique rays

3.3 Sun Angle, Duration, and Insolation

Direct rays at 23.5o N Direct rays at equator

3.3 Sun Angle, Duration, and Insolation

• The Seasons– Summer Solstice (~ June 21) in N. hemisphere

• Direct rays at 23.5o N (Tropic of Cancer)• Northern hemisphere receives more energy• 24 hours of sunlight (Arctic Circle to North Pole)• Longest day of the year in N. hem. • Shortest day of the year in S. hem.

– Autumnal Equinox in (~ Sept. 22) N. hem.• Direct rays at equator• 12 hours of daylight everywhere

3.3 Sun Angle, Duration, and Insolation

• The Seasons– Winter Solstice (~ Dec. 21) in N. hemisphere

• Direct rays at 23.5o S (Tropic of Capricorn)• Southern hemisphere receives more energy• 24 hours of sunlight (Antarctic Circle to South Pole)• Shortest day of the year in N. hem. • Longest day of the year in S. hem.

– Vernal Equinox in (~ March 20) N. hem.• Direct rays at equator• 12 hours of daylight everywhere

The Seasons (Focus on Solstices)

The Seasons (Focus on Equinox)

Duration of daylight for certain Latitudes

3.3 Sun Angle, Duration, and Insolation

• Sun’s declination: Latitude at which the sun is directly overhead

• Analemma: Shows the sun’s declination throughout the year.

• What is the declination on Oct 10th?

3.3 Sun Angle, Duration, and Insolation

• Variations of Insolation with Latitude– Tropical Zones– Middle latitude zones– Polar zones

• Which zone(s) would have the least annual variation?

Ancient Civilizations (Mayan Pyramid)

Physical Geography

End of Chapter 3: Earth-Sun Relationships and Solar Energy