Transcript Earth-Sun Relationships - Los Angeles Mission College

EARTH-SUN
RELATIONSHIPS
Insolation, Day-Night and Seasons
1. Cosmic Connections:
Earth, Solar System and Beyond
2. The Sun and Solar Radiation:
Insolation, Solar Energy
3. Inclinations and Movements of Earth:
Day-Night, Length of Day, Seasons, Latitudinal Zones
1. COSMIC CONNECTIONS:
EARTH, SOLAR SYSTEM AND BEYOND
What is the Earth’s relationships with the Sun and other heavenly
bodies?
How do phenomena like day and night, seasonal variations,
climatic variations, and certain atmospheric anomalies
happen?
• Earth is almost entirely dependent on the Sun for its existence!
• Earth, together with seven other planets, form our Sun’s
Solar System
Our Solar System comprises all celestial bodies surrounding and
orbiting the SUN, (star) due to the star’s dominant mass and
gravitational attraction.
• And our Sun is one of an estimated 400 billion stars that make up
our
Galaxy – the Milky Way Galaxy.
• All the stars that you see on a clear night are part of our
Milky Way Galaxy
• Galaxies are sprawling space systems composed of countless
clusters of stars, dusts and gases
• Billions of galaxies – so far apart that measured in light years
(1 light year = 6 trillion miles; speed of light is 186,000 mps)
• The closest galaxy to ours is 75,000 light years away
• Some of these distant systems are similar to our own Milky Way
Galaxy, while others are quite different
These are, then, our planet’s –
Cosmic Connections
Earth and the Solar System
• All the planets revolve around the Sun in the same direction
• All the planets lie in a common plane – the Plane of the Ecliptic,
and the orbits of the planets are nearly circular
 The Sun has a relatively slow rotation [What happened to Pluto?]
Inner planets are made of rocks
and metals – Terrestrial Planets
Outer planets are made of gases
and ices – Gas Giants
Our solar system also includes about 138 satellites (like our moon),
numerous asteroids, as well as comets and meteors (“shooting stars”
and meteorites)[Does our moon have any impact on our environment?]
2. THE SUN AND SOLAR RADIATION
The Sun and Its Energy
• The sun is a self-luminous sphere of gasses that emit radiant energy.
• It is like a giant thermonuclear furnace with fusion reactions,
and a core temperatures exceeding 27,000,000˚ F
• At its luminous outer surface, the Photosphere, temperatures fall to
10 -11,000˚F – then the Chromosphere, and then the Corona
• Charged particles (protons & electrons) from the corona flow along the
sun’s magnetic field lines into space as Solar Wind – interacts
with ions in earth’s outer atmosphere to produce the colorful light
shows, the Auroras (Aurora Borealis and Aurora Australis)
• Sunspots, caused by magnetic storms on the sun, are dark regions on
the photosphere, 15000 C - 20000 C cooler than the surrounding,
and they signify increased solar activity, peaking in 11- year
cycles – the next peak is estimated to be in 2012
(Remember the recent movie, “2012” ?)
Solar Flares (as well as other prominences and coronal mass ejections)
occur in the region of sunspots, sending out energized, charged particles
at great speeds toward the earth. . .
Insolation and Atmospheric Dynamics
• Incoming solar radiation, or insolation, is the major source of energy
both directly and indirectly for the entire solar system
The rate of a planet’s receipt of solar energy is called the solar constant
• Energy is emitted by the sun in the form of electromagnetic energy,
travelling in a spectrum of varying wavelengths, taking about
8.3 minutes to reach earth
• This radiant energy is largely shortwave radiation, composed of
Ultraviolet rays, X-rays and Gamma rays (9%); visible light
(41%); various infrared wavelengths (49%); and microwave,
television and radio wavelengths (1%)
• Earth receives only 1/2,000,000,000 (one two billionth) of the sun’s
radiation, but that’s what drives much of the atmospheric,
physical and biological processes of the earth system
A Portion of the Electromagnetic Spectrum of Radiant Energy
 Spatial and Seasonal Variations in Insolation
over the surface of the earth depends largely on 3 factors:
• Duration of daylight (varies by latitudes and seasons);
12-hour days year-round at the equator, greater variability
toward the poles, with the poles experiencing essentially
one long 6-month long day, and a similarly long night
• Angle of solar rays (which affects intensity); and
Caused by earth’s inclination, rotation, revolution
• Earth’s atmosphere (some radiation is absorbed by clouds,
some reflected back).
Unlike solar radiation, earth radiation is longwave
 The first two factors above relate to the third aspect of Earth-Sun
Relationships – Inclination and Movements of Earth
– and their Implications
3. INCLINATION AND MOVEMENTS OF
EARTH:
Day-Night, Length of Day, Seasons, Latitudinal Zones
Five Important Factors or Determinants:
1. SPHERICITY
2. ROTATION
3. AXIAL TILT – INCLINATION
4. AXIAL PARALLELISM
5. REVOLUTION
1. SPHERICITY
Earth appears as an oblate
spheroid to the Sun’s
parallel rays; the geoid
Effects of Earth’s
2. ROTATION
 The Earth rotates on its axis
 One complete rotation (3600) takes
approximately 24 hours
 Rotation is from West to East
Sun appears to ‘rise’ in East and ‘set’ in West

3. AXIAL TILT – INCLINATION
and Plane of Ecliptic
Earth’s axis is tilted about 23.5˚ from
perpendicular to Plane of Ecliptic;
4. PARALLELISM
Earth’s axis remains in a fixed alignment with Polaris directly
overhead, throughout the year, as it revolves about the Sun
5. REVOLUTION
 The Earth revolves around the Sun in one year (365.25636 days)
 The Earth’s revolution is slightly elliptical, not circular –
Direction of revolution is counter-clockwise
 Earth moves in a constant plane – Plane of the Ecliptic – in its revolution
about the Sun – Earth’s Orbit
The Orbit of the earth is an elliptical path along the Plane of Ecliptic
Average orbital length = 940,416,480 km
Closest approach to the Sun = 147 million km, Perihelion (January 3)
Farthest distance from the Sun = 152 million km, Aphelion (July 4)
Implications and Effects:
 Alternating Day and Night
– Circle of Illumination
 Length of Day
– Variations due to:
 Inclination of earth’s axis
 Plane of Ecliptic, and Parallelism
 Earth’s revolution around the sun,
which results in:
 2 Solstices (Summer, Winter)
 2 Equinoxes (Vernal, Autumnal)
[See: Figure 3.17 in Text,
and Read the Explanation ]
In the Northern
Hemisphere,
A: Summer
Solstice*
B: Autumnal
Equinox
C: Winter Solstice*
D: Vernal Equinox
*During the 2 Solstices,
the situations are reversed
in the Southern
Hemisphere
Percentage of Insolation
striking various latitudes
during an equinox
The Sun’s Rays in
Summer (b) and Winter
(c)
GALACTIC MOVEMENT:
• Earth’s axis wobbles through (22˚-24.5˚) time and will not always
maintain a constant angle
• Earth’s orbit around the sun will also change from more circular
to more elliptical (Milankovitch Cycles)
[Explains Cycle of Ice Ages?]
• Why?
•Effects of
Galactic Motion?