Origin of the Earth
I. What do we know about the origin of the
universe?
- A. Scientific evidence favors the Big
Bang
theory for the origin of the universe
- 1. At one time all matter in the
universe
was contained in a small point
- 2. The Big Bang occurred and
matter contained
in the original small volume expanded rapidly, and has been doing so
ever
since.
- 3. The Red Shift is the
most important
piece of evidence supporting the Big Bang. What is the Red Shift?
- a. The Red Shift is a product of
the Doppler
effect.
- b. The Doppler effect is a
change in frequency
with which waves from a given source reach an observer when the source
and the observer are in rapid motion with respect to each other so that
the frequency increases or decreases according to the speed at which
the
distance is decreasing or increasing (definition from Merriam-Webster
Collegiate
Dictionary)
- c. An example of the Doppler
effect can be
found in the sound that a passing train makes.
- i. As the train approaches the
listener, the
sound waves become compressed with respect to the listener, and the
train
whistle has a higher pitch
- ii. When the train passes the
listener, the
sound waves grow longer, and the train whistle now sounds lower in
pitch.
- d. When galaxies move rapidly
away from our
own galaxy, they acquire a more reddish color as light waves acquire
longer
wavelengths. Galaxies moving rapidly toward our Milky Way Galaxy appear
to be more bluish in color because light waves acquire a shorter
wavelength.
- e. Because most of the galaxies
appear to
be shifted more toward the red end of the visible spectrum, the
phenomenon
is called the Red Shift.
- B. The universe is thought to be
10-20 billion
years old based on how fast you think the universe has been expanding.
II. How did our Solar System form?
- A. When a sizable amount of dark,
gaseous
matter accumulates, a strong gravitational anomaly occurs, and more
matter
is drawn to the accumulated mass to become a new star.
- B. The additional accumulation of
matter increases
the gravitation and spin acceleration of the mass.
- C. As the acceleration increases,
matter is
spewed out into a disc-shaped cloud, and this material eventually
develops
into planets.
III. How did the Earth form?
- A. Matter condensed from solar
nebula
- 1. This matter was probably
something like
carbonaceous
chondrite meteorites that fall to the Earth. Chondrites are a
special
kind of meteorite that has small rounded globs (about half a cm or
less)
called chondrules.
- 2. Carbonaceous chondrites are
meteorites
that are similar to the Sun in composition, after you take away the
hydrogen
and helium.
- 3. Evidence suggests that this
occurred about
4.7 billion years ago, because the oldest carbonaceous chondrites are
this
old.
- B. Bits of condensed matter
collided or accreted
to form a small undifferentiated planet. This marked the beginning of
the
period of cataclysmic bombardment, which lasted for almost a billion
years.
Most of the craters of the moon were formed this way.
- C. Differentiation of a molten
Earth caused
layers to separate out
- 1. The heavier elements, like iron
and nickel,
sank to the center to form the core
- 2. Lighter elements like aluminum
and silicon
rose to the surface and formed the crust.
- D. In time the Earth cooled.
IV. How did the Moon form? There are
four general theories for the Moon's formation that scientists have
entertained.
- A.
Earth's gravitation captured a passing body into its orbit
- B. While
Earth was still a molten mass (lava ocean), material from
Earth spun off to become the Moon.
- C. As
Earth formed through accretion (building up from the joining
of smaller pieces), the Moon also formed through accretion within the
vicinity
of Earth.
- D. A
Mars-sized object collided with Earth, splashing lunar material
into orbit around Earth.
- 1. This is the favored explanation for the formation of the
Moon
- 2. It comes from comparing the composition of Moon
rocks (from Apollo
missions) to appropriate rocks here on Earth.
- 3. The Moon is similar enough in composition to Earth
to eliminate the possibility
of the Moon being formed separately.
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