Foundations of the Big Bang
theory |
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General
Relativity and the "Cosmological Principle" give rise to the Big Bang
theory. |
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The Big Bang
theory makes definite predictions for the structure and evolution of the
universe that depend on the nature and amount of matter in the
universe. |
Observational tests of the Big Bang
theory |
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A
cosmological constant and the Hubble Law. |
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The Big Bang
theory makes definite predictions for the types and amount of matter in
the universe. |
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The early
universe should have been very hot. The cosmic microwave background
radiation is the remnant heat leftover from the Big
Bang. |
Limitations and extensions of the Big Bang
theory |
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The Big Bang
theory makes no attempt to explain how structures like stars and galaxies
came to exist in the universe. |
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Fluctuations in the cosmic microwave background (CMB)
radiation |
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The
temperature of the CMB is observed to vary slightly across the sky. What
produced these fluctuations and how do they relate to stars and
galaxies? |
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A very short,
but especially rapid burst of growth in the very early universe
(“inflation”) provides an elegant, yet untested, explanation of the above
puzzles. |
Our universe |
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The amount
and type of matter in the universe is fundamental in determining the
properties of our universe. How much matter is there? Is it mostly
“ordinary” matter (composed of protons, neutrons, electrons and/or
photons) or a more exotic form not yet observed in the
laboratory? |
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How fast is
the universe currently expanding? How do we measure
this? |
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We can
estimate the age of the universe from its current expansion rate. We can
place a lower limit to the age of the universe by estimating the age of
the oldest known stars. Are these numbers
compatible? |
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Is our
universe open and infinite, closed and finite, or just hovering on the
flat boundary between the two? |
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Rather than
slowing down, the expansion of our universe appears to be speeding up! One
possible source of this acceleration is a form of energy called the
“cosmological constant”, or a variant of it called
“quintessence.” |
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How did we
get from the Big Bang to the human search for extraterrestrial
life? |
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Will the
universe continue to expand forever, or eventually
collapse? |
Related topics |
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When did the
first objects form in the universe? |
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A brief tour
of our own Milky Way galaxy, with a beautiful image of it from the COBE
satellite. |
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Learn how
stars form, live and die. |