Download Stars & Galaxies

Origins of the
Earth, Oceans, and Life
Unit 2
Big Bang Theory
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Universe had a beginning
Occurred 15 billion years ago
Started the expansion of the universe from a
geometric point.
• Expansion continues today
• A billion years later the stars and planets
congealed
Stars & Galaxies
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Galaxies
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huge rotating aggregations of stars, dust, and gas
held together by gravity.
Probably 50 billion galaxies with 50 billion stars in
each
Our galaxy is the spiraled Milky Way
Galaxies can be elliptical, irregular, and spiral
Stars
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massive spheres of incandescent gas
There are more stars in the Milky Way than grains of
sands on all beaches
The sun is a typical star
Stars cont.
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Condensation Theory- how stars and planets were
formed
Stars form in a nebula (cloud of cold dust and gas within
a galaxy)
1. The nebula shrinks under its own weak gravity
2. Increases the temp and nuclear fusion turns H He
3. Liberates energy (this is why stars shine)
4. Stops shrinkage and stars become somewhat stable
5. As star converts more H into heavier elements the
energy output rises and the body of the star swells
into a “red giant”
6. Star’s core will eventually collapse in an explosion
(star blows up)- supernova
Every chemical element that made the planets, stars,
oceans, and organisms is made up of star dust.
Formation of Solar System
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Inner material concentrated into a protosun and
outer material formed outer planets
 Planets formed through accretion - clumping
smaller particles into larger masses.
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Accretion period lasted 50-70 million years
Earth and ocean are an indirect result of a
supernova explosion (solar nebula)
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A solar nebula is like a spinning skater that brings
their arms in.
Earth & Ocean
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Earth was heated by kinetic energy of falling debris and decay of
radioactive elements within the newly formed Earth, causing it to melt
density stratification - Iron sunk to the middle of the planet (developing
gravity field), and lighter minerals (Si, Al, Mg) migrated to the surface
forming the Earth’s crust
At 4.6 bil years, first surface formed
Outgassing (release of volatile substances and water vapor) occurred
everywhere and caused massive clouds in upper atmosphere
No liquid water was on the Earth, intense lightening occurred, and sunlight
couldn’t penetrate the clouds surrounding the Earth.
Eventually, clouds cooled and formed water droplets that fell to the Earth,
but boiled back into the clouds once they touched the Earth
Once the surface of the Earth cooled, water collected in basins and also
dissolved minerals from rocks.
Heavy rains fell for 10 million years to eventually form the oceans
Early atmosphere included methane, ammonia, carbon dioxide, water
vapor, and other gases
Origins of Life
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Stanely Miller’s experiment in 1953
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Mixed the early atmosphere gases in a closed container with a spark
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In a short time amino acids, small proteins, and nucleotides formed.
Life did not form from Miller’s experiment, but the building blocks of life did
All life needs water and saline (for cells)
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therefore it is widely accepted that life arose somewhere in the early
ocean
Early steps of organisms forming from organic building blocks is called
biosynthesis
Evaporation of water, concentration of amino acids and nucleotides could
be formed in a rich organic soup
John Corliss suggests that heat energy from thermal vents in the sea (high
concentrations of minerals) could have formed into complex molecules of
life
Oldest fossils are 3.4-3.5 Billion years old of bacteria-like organisms
Ocean World
 Reasons
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why the Earth is ideal:
Distance from sun allows for liquid water
Temp just right because of sun
Gravity force is just right
Single moon provide for gentle tides
Atmosphere clear so sun can penetrate
Ozone layer protects us from UV
Material that accreted had minerals and water
to form the Earth’s crust
Future of Earth
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billion years from now, the sun (as a red
giant) will probably engulf the inner planets
and burst.
“How We Know…”
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Edwin Hubble – made discovery that distant stars and galaxies are
receding from the Earth in all directions. This implies that the
universe is still expanding.
Planetsimals are aggregations of gas and dust which may be
several hundred kilometers in diameter. Earth is believed to have
been formed by aggregations of planetsimals.
Zircon crystals found in Australia are the oldest rocks. They are 4.3
billion years old. Scientists cannot measure the age of the Earth by
measuring the oldest rocks because those rocks were probably
“recycled”. The Earth’s oldest rocks are found on all the continents.
Some include 4.030 billion years old in Canada and 3.7-3.8 billion
years old in Greenland.
The moon has a tiny metallic core because it is believed it broke off
from the earth when it was hit by a meteoroid when it was about half
formed.