The Universe

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The Universe and Everything Else
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Part One Cosmology
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Definition Cosmology (Cosmos The heavens,
ology The study of)
The study of the origin, evolution, structure
and future of the universe.
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Aristotle (384-322 BC) Philosopher and
Mathematician
The Earth is a sphere. It is surrounded by
concentric celestial spheres. Stars are attached
to these spheres and the spheres rotate around
the Earth
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Ptolemy (2nd Century CE) Mathematician,
Astronomer and Astrologer
Planets move around the Earth, but also on their
own epicycles. Ptolemy also thought that some
objects might orbit the sun. This system was
incorrect, but it allowed for precise
calculations of where the planets would appear in
the sky.
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A planet in orbit around the Earth and on an
epicycle of its own.
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Tycho Brahe (1546-1601) Astronomer and Alchemist
Believed that the planets orbited the sun, but
that the sun (and planets orbiting it) orbited
the Earth.
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The Earth (middle) is orbited by the moon, and
also the sun (with other planets orbiting the
sun). Note the celestial spheres on the outside
where the stars are attached.
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Nicolaus Copernicus (1473-1543) Astronomer
Copernicus was the first to develop a
comprehensive sun-centered model of the solar
system. He believed that all of the planets
(including the Earth) were heliocentric.
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Circular orbits around the sun. Notice that
Copernicus still had a celestial sphere in his
model
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Johannes Kepler (1571-1630) Mathematician,
Astronomer, and Astrologer
Kepler used physics and mathematics to improve
Copernicuss model. Kepler realized that the
force of gravity between the planets and the sun
forced planets into elliptical orbits.
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Planets get slower as they move away from the
sun, but then speed up on the way back. This is
an effect of gravity and it produces elliptical
orbits.
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Isaac Newton (1642-1727) Physicist and
Mathematician
Newton developed a new form of mathematics that
helped to explain how gravity works. His ideas
proved that Kepler was right. What Kepler
observed, Newton proved.
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Newton worked out his famous laws of physics
while his university was closed due to the Black
Plague. Although Einstein later found that
Newtons laws were incomplete, they are good
enough for most calculations and are still used
today.
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Albert Einstein (1917) Theoretical Physicist
Einstein built on Newtons work. He came up
with a new theory about how gravity works. He
said that large masses curved space which meant
that large objects would fall towards each other.
Although his equations could be used to show
that the universe was probably expanding, he
first chose to believe that the universe was
stable (not expanding).
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The Earth orbiting the sun due to the curvature
of space created by the suns mass.
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George Lemaitre (1927-1931) Catholic Priest,
Astronomer, and Physicist
Lemaitre used Einsteins equations to prove that
the universe was expanding. In 1931 he published
a paper on the Primeval Atom. This later
became known as the Big Bang theory.
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Edwin Hubble (1920s and 30s) Astronomer
Hubble discovered that light from neighboring
object in space had a Red Shift which meant
they were moving farther apart. Objects far away
were moving faster and objects closer were moving
slower.
This was the first evidence that the Big Bang
theory might be accurate and that the universe
was small in the past and is expanding today.
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Light from an object moving closer has a shorter
wavelength (blue shift). Light from and object
moving away has a longer wavelength (red shift).
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Part Two The Big Bang
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During the first picosecond (0.000000000001s) of
the Big Bang, the universe began to expand from a
small point called a singularity (similar to a
massive black hole). Because things were so
compressed, only energy existed.
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At first their was only one force holding
everything together, but as the universe expanded
the temperature cooled and this force broke into
the four fundamental forces that scientists are
aware of today.
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Before the end of the first full second, the
universe has cooled down to a point where energy
had began to change to matter. The first form of
matter was probably quarks which are the building
blocks of larger pieces of matter.
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Some quarks came together to form the first
protons.
Hydrogen was the first (and still is the most
abundant) element in the universe because it has
the simplest nucleus (one proton).
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Sometime before the first hour was finished,
helium also was formed. Hydrogen atoms came
together in early stars to form this element, the
second most abundant in the universe. The
process is called fusion.
Even today, nearly 100 of the mass in the
universe is hydrogen or helium
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After about 1 million years, electrons have
formed and are joining with protons and neutrons
to form stable atoms.
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At this point, the universe has also cooled down
enough so that energy is not interacting (or
changing into) matter at anywhere near the rate
at which it did in the beginning.
The amount of matter formed in the universe gives
it shape. Too much matter, and the universe
would curve in on itself, to little and it would
form a shape like a saddle and continue forever.
For reasons we cant yet fully understand there
was just enough matter to form a flat universe.
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After about 100 million years the stars begin to
shine, and at 600 million years stars have begun
to come together to form the first galaxies.
Our own sun was not formed until about 9.1
billion years after the beginning.
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Most scientists believe that it has been about
13.7 billion years since the Big Bang began.
Humans, the Earth, and even the sun have only
existed for a very small sliver of those 13.7
billion years.
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Consequences of the Big Bang
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Scientists believe that the Universe is infinite
or so big that we can consider it to be infinite.

The stars we see at night are only a small
fraction of the universe. Most of the stars are
so far away that their light hasnt made it to
Earth yet. Because the Universe is expanding, we
may never see them.
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Thought Experiment
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The possibility of life existing elsewhere in the
universe is extremely high. In fact, the
universe is so big that there are probably copies
(repeats) of our own Earth or even of you.
The problem is that the universe is so large that
we may never see other life forms even though the
likelihood of their existence is extremely high.
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Will it end? How?
As the universe continues to grow, we should also
ask another question How does it all end? Many
scientists refer to the end of the universe as
Heat Death.
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The Heat Death theory states that as the universe
expands, matter will cool down and begin to
decay.
Billions of years from now, even protons and
neutrons will begin to break down. Even black
holes will dissipate and fall apart.
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As the universe expands matter and energy will
spread out so much that the chances of matter
bumping into each other will become increasingly
unlikely.
Without these interactions, the universe will
become an increasingly dull place to the point
where all action stops. The temperature will
drop to a level almost at absolute zero.