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The Earth’s Place in Space
The Earth’s Place in Space
3 Sources of Energy to the Earth:
1. Sun
2. Geothermal
3. Tides
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•Sun’s energy
– created by nuclear fusion in the sun’s core.
– reaches earth by radiation (external processes).
– drives weather, climate, erosion, photosynthesis.
•Geothermal energy
– created by radioactive decay (nuclear fission) in the earth’s core.
– moves by conduction & convection (internal processes).
– drives volcanism, plate tectonics.
•Tidal energy
– caused by gravitational attraction between the earth’s oceans and the
moon and sun.
– drives some coastal currents and processes.
Energy Flow
• Solar Energy (99.985% of Earth’s
energy)
• Geothermal Energy (0.013%)
• Tidal Energy (0.002%)
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Sources of energy to the Earth
Energy Source
Tidal
Geothermal (total)
Conduction
Convection
Sun (total)
Reflected
Land, air and
sea heating
Evaporation
Photosynthesis
Energy (1012 Watts)
2.7
32.3
21.0
11.3
173,000
52,000
81,000
*
*
***
39,960
40.0
Enough energy output by the Sun per second to meet the
total electricity demands of the U.S. for 200,000 years!
Our neighborhood
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Origins of our Solar System
– Universe formed 10-15 billion years b.p.
– Solar system (including Earth) formed 4 -5
(4.6) billion years b.p. from nebula
Planetary Accretion
– Order of formation
– Sun (hydrogen)
– inner planets (silicates, oxides, iron-nickel alloys)
– outer planets (sulfur, water, methane, ammonium)
The Universe
• 12-15 billion years old
• Millions of galaxies
• 400 billion solar systems in galaxy
• 9 planets + 61 moons in solar system
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Birth of the Milky way
Our Solar system
developed 4.6
billion years ago
when the gases of
a nebula started to
contract and rotate
because of
gravitational
attraction, the
sun’s fusion
started, and later
the planets
condensed.
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2 Basic Types of Planets
1. Terrestrial Planets
Mercury
Venus
Earth
Mars
2. Jovian Planets
Jupiter
Saturn
Uranus
Neptune
Pluto
Planets differ in density and composition
6
Density (g cm- 3)
5
4
3
2
1
0
Mer Ven Ear Mar Jup Sat Ura Nep Plu
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Characteristics of the orbits of the planets…
Kepler’s Law of Orbital Harmony
p2 = k d3
The farther away
from the sun you
are, the longer it
takes to
complete one
full revolution
around the sun.
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Kepler’s Laws of Planetary Motion
Law of Ellipses
All the planets’ orbits are elliptical
All have elliptical orbits
94.5
million
miles
SUN
91.5
million
miles
Aphelion
Perihelion
Average distance = 150 million km
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All rotate in the same direction (moons + sun too)
Exceptions = Venus, Uranus, & Pluto rotate slowly clockwise
Rotation of sun, planets, & their moons is all in
the same direction
EARTH
SUN
MOON
All revolve about the sun in the same direction.
b. Law of Equal Areas
The orbits are nearly circular, but not quite, and the
planets travel slightly faster while they are closer to the
sun than when farther away (because of the increased
gravitational attraction).
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Newton’s Law of Gravitation
M1 M2
F
= G
R2
Gravitational constant
G = 6.672 x 10-11 N m2 kg-2
6.672 x 10-8 cm3 g-1 s-2
Bode’s Law of Planetary
Distance
Inner planets in such a hot zone close to the sun
when they formed that only metals and rocky
silicates could condense out and aggregate into
planets. Farther out where it was colder, water
and lighter “gases” could condense out to form
the Outer Jovian Gas Giants.
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