Transcript Earth as a Planet

Announcements
• Don’t forget to take the test! (today, tomorrow,
Friday before class)
• Don’t discuss the test with classmates until
class on Friday.
• Pick up graded homework.
• First project due in 9 days!
Earth as a Planet
4 October 2006
Course Outline
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Naked-eye astronomy
Crash course in physics
Our solar system
The stars
Structure and history of the
universe
Course Outline
•
•
•
•
•
Naked-eye astronomy
Crash course in physics
Our solar system
You are
here
The stars
Structure and history of the
universe
Today:
• Some important characteristics of Earth
to keep in mind as we compare it to
other planets
The planets, to scale
Earth
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My favorite planet
Largest known rock
Very geologically active
Atmosphere of nitrogen
and oxygen
• 3/4 covered with water
• Nice, comfortable surface
temperature
• Only known home of life
Earth: Geology
Earth: Geology
Earth: Geology
Earth
• Made of rock (why?)
• Hot inside (why?)
• Atmosphere of nitrogen
and oxygen (why?)
• 3/4 covered with water
(why?)
• Nice, comfortable surface
temperature (why?)
Some partial answers
• Made of rock because heavy atoms (Si, O, C, Ca, Na,
K, Fe, Mg) tend to form rocks, and light atoms (esp. H,
He) are uncommon on earth (why?)
• Hot inside because of radioactive decay of rare atoms
(U, Th, K, Rb), plus some residual heat from earth’s
formation; heat builds up and escapes slowly due to
earth’s size
• Atmosphere of nitrogen (N2) and oxygen (O2) because
plant life has removed most carbon dioxide (CO2) and
produced oxygen
• 3/4 covered with water because of size and surface
temperature
• Nice, comfortable surface temperature because of our
distance from the sun
Earth: Life
Earth’s Moon
• 1/4 earth’s diameter
• 1/80 earth’s mass
• Covered with craters,
ancient lava flows
• Geologically inactive
• No atmosphere
• Essentially no water
• Hot days, cold nights
• Only other world humans
have visited