Cosmology: The Origin and Evolution of the Universe
Guiding Questions
The darkness of the night sky tells us about the nature of the universe
The universe is expanding
The Hubble law describes the continuing expansion of space
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The redshifts that we see from distant galaxies are caused by this expansion, not by the motions of galaxies through space
The redshift of a distant galaxy is a measure of the scale of the universe at the time the galaxy emitted its light
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The expanding universe emerged from a cataclysmic event called the Big Bang
The observable universe extends about 14 billion light-years in every direction from the Earth
The microwave radiation that fills all space is evidence of a hot Big Bang
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The background radiation was hotter and more intense in the past
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The abundance of helium in the universe is explained by the high temperatures in its early history
The shape of the universe indicates its matter and energy content
If ρ0 is greater than ρc, the density parameter Ω0 has a value greater than 1, the universe is closed, and space is spherical (with positive curvature)
If ρ0 is equal to ρc, the density parameter Ω0 is equal to 1 and space is flat (with zero curvature)
If ρ0 is less than ρc, the density parameter Ω0 has a value less than 1, the universe is open, and space is hyperbolic (with negative curvature)
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Observations of temperature variations in the cosmic microwave background indicate that the universe is flat or nearly so, with a combined average mass density equal to the critical density
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Observations of distant supernovae reveal that we live in an accelerating universe
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Primordial sound waves help reveal the character of the universe
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Key Words
Author: Michael Cohen
E-mail: mrcohe@ship.edu
Homepage: http://physics.ship.edu/~mrc/