1. The Earth and Other Planets

2. The Earth and Other Planets
Our Solar System
Sun / Terrestrial Planets / Jovian Planets
TERRESTRIAL PLANETS
Mercury
Venus
Earth
Mars
The terrestrial planets all tend to be fairly small, have few moons, and are solid and rocky.

3. The Earth and Other Planets
JOVIAN PLANETS
Jupiter
Saturn
Uranus
Neptune
The jovian planets all tend to be quite large, have several moons, are primarily made of layers of gases which become denser further down, and may have a small solid core.

4. The Earth and Other Planets
NEBULAR THEORY
Theory re formation of solar system:
As dust and gas clouds collected due to gravitational forces, they began to rotate and flatten into a disk. The majority of mass collected in the center, and the planets began as mass concentrations orbiting the dense central body.
Where did the dust and gas clouds come from?
Many believe the dust and gas originated in the events that occurred when the universe first formed.
How old is our solar system?
Approximately 4.5 billion years old.

5. The Earth and Other Planets
DEBRIS THAT DID NOT BECOME PLANETS
Asteroids
Small
Rocky
In a “belt” between Mars and Jupiter
Comets
Ice and dirt
Circle the sun outside of Pluto
Halley’s comet is best known
Meteors
Small pieces of debris
Orbit the sun
Burn if fall into earth’s atmosphere
Meteorite
A piece of rock big enough to reach earth’s surface .

6. The Earth and Other Planets
THE EARTH’S MOTION
Revolves around sun
Travels in an elliptical orbit
Takes approximately 365 days to complete 1 orbit
Rotates on axis
Angle of rotation tilts 23°
Takes approximately 24 hours to complete 1 spin
Precesses
Spinning on axis in a circular pattern
Completes circular pattern once every 23,000 years
THE EARTH’S MOON
Orbits earth
Has synchronized rotation and revolution with earth
Takes approximately 1 month to complete 1 orbit
Phase of moon is based on how mush of lighted side we can see
Has 1/6 of the gravitational pull of the earth
Mutual gravitational influence
Pull on earth’s surface waters creates tides

7. The Earth and Other Planets
THE EARTH’S MOTION
Revolves around sun
Travels in an elliptical orbit
Takes approximately 365 days to complete 1 orbit
Rotates on axis
Angle of rotation tilts 23°
Takes approximately 24 hours to complete 1 spin
Precesses
Spinning on axis in a circular pattern
Completes circular pattern once every 23,000 years
THE EARTH’S MOON
Orbits earth
Has synchronized rotation and revolution with earth
Takes approximately 1 month to complete 1 orbit
Phase of moon is based on how mush of lighted side we can see
Has 1/6 of the gravitational pull of the earth
Mutual gravitational influence
Pull on earth’s surface waters creates tides

8. The Earth and Other Planets
THE EARTH’S INTERIOR
CRUST
Outer layer
6 to 45 miles thick
Made of lightest materials
Solid
Approximately 70% covered with water
MANTLE
Below crust
High temperatures
Solid in upper region, thick liquid of melted rock below
Widest layer
OUTER CORE
Below mantle
Very high temperatures
Liquid
Iron – nickel
INNER CORE
At the earth’s center
Extremely high temperatures
Solid due to tremendous pressure
Primarily iron, some nickel

9. The Earth and Other Planets
HOW “LIFE” ON EARTH BEGAN
GEOLOGIC TIME FRAME (see Time Scale shown in text, p. 631)
Covers the 4.5 billion years of Earth’s existence
Life not possible initially due to high temperatures, lack of proper atmosphere, no available water, continuous bombardment from space
As earth cooled and impacts lessened, land and sea formed
First living organisms appeared in oceans about midway through the earth’s history
Gradually oxygen began to accumulate in atmosphere
Ozone layer began to form
Life forms appeared on land less than 500 million years ago
Principal vertebrate life froms on earth were reptiles fro 65 million to 250 million years ago
Mammals began to dominate the earth in the last 65 million years
Human ancestors first appeared less than 2 million years ago
HUMAN TIME FRAME
Modern human species less than 50,000 years old
Recorded human history available for past 4000 years only
Human influence on the earth’s ecosystems which support life insignificant until the Industrial Era beginning 250 years ago