Transcript Origin of the Universe

Origin of the Universe
the Big Bang
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The universe came into
existence suddenly. The
common scientific theory is that
the universe existed in a
concentrated single point,
containing all known matter and
energy. Approximately 13.7
billion years ago, this single
point began to expand – an
event that has become known
as the Big Bang.
It took about 1 million years for the matter
in the universe to cool enough for the first
elements to form.
 Most of the new matter was hydrogen and
helium – two very simple elements.
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a protostar
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Theory says that matter accumulations
became denser as gravity pulled them
together. As the density increased, the
matter collapsed and compacted under its
own weight, causing a warm, dense core
called a protostar.
How do scientists theorize that the
first stars formed?
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Given enough mass, protostars continue to
contract, becoming denser until the core
pressure and density were so high that nuclear
reactions began. The nuclear fusion reaction
from protostars creates the stars.
Nuclear fusion is a reaction in which light atoms
unite to form heavy atoms, releasing
tremendous energy in the process.
Nuclear fusion and the theorized “life
cycle” of stars provide an explanation of
how heavy elements formed in a universe
filled predominantly with helium and
hydrogen.
 Once nuclear fusion begins, a star burns
for millions of years, consuming the
hydrogen within it.
 Astronomers theorize that heavy elements
form as hydrogen bonds fuse.
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the hydrogen becomes exhausted, the
star’s core becomes denser. It eventually
collapses under the extreme gravity forces
generated by the density. This may cause
a large nuclear explosion called a
supernova.
 The explosion generates heavier atoms.
The fusion core collapses and in the
supernova, massive stars account for the
origin and distribution of heavy elements
throughout the universe.
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Origin of the Solar System
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Formation
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The current theory among many scientists is that the
solar system’s current form, with planets orbiting the
sun, began with a large cloud of hydrogen and helium
called a nebula.
a. The shock wave of the supernova caused the cloud
to condense, which caused it to spin. As the cloud
collapsed and became denser, it flattened into a disk
due to rotation. At the center a protostar developed
which when dense enough began nuclear fusion and
became the sun.
Some of the gas continued to revolve
around the sun, eventually condensing
into masses too small to become stars.
This is what formed the planets.
 The nebular theory is the theory that the
solar system originated as a nebula.
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Origin of the Earth and Moon
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According to the nebular
theory, Earth and the other
planets formed through
accretion.

Accretion is the process by
which small particles clump
together because of gravity.
As a mass grows due to
accretion, the more gravity it
has, and the more additional
mass it attracts.
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Although the Earth didn’t gain enough
mass to form a protostar or star, its
growing mass caused its core to
compress. The core heated and became
molten liquid.
 The
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outer core is still molten
Within the molten liquid, heavy matter,
such as iron and nickel, sank toward the
center, while light matter, such as oxygen
and silicon, moved towards the surface.
 The
process of density stratification formed
the layers of the Earth.
Formation of the moon
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The most widely accepted explanation for the moon’s
origin is the Orpheus theory.
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A planet-sized body – possibly another planet about one-third
the size of Earth – struck Earth during its early development and
sent some of its material into orbit, forming the moon.
Origin of Atmosphere and
Oceans
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Early Earth had no atmosphere
 Earth
was mostly molten liquid and gases did
not escape.
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Eventually it cooled enough for the surface
to solidify into a crust.
 After
the crust solidified, gases were released
by volcanic activity. These gasses
accumulated as an early atmosphere of
primarily water vapor, carbon dioxide, and
nitrogen.
 No water could be found do to the high heat
o
Rain would boil as soon as it hit the ground
The Oceans
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After further cooling, Earth’s surface
allowed rain to accumulate and the oceans
formed as water vapor condensed.
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Some scientists speculate that additional
water may have entered Earth’s atmosphere
via comets and other ‘outside’ sources.
Scientists believe that the development of oceans
began the process that allowed life to form
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Carbon dioxide dissolved into the young oceans,
leaving a nitrogen-rich atmosphere.
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Many scientists think that these were the conditions
required for life.
There was no oxygen in the atmosphere on
early Earth.
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Although oxygen is essential to almost all life today,
according to data recorded in rock, early life didn’t
use oxygen.
Oxygen entered the atmosphere about 1.5 billion
years ago when photosynthesizing organisms began
using carbon dioxide and releasing oxygen.