The Cosmic Web - Evening Lecture at Sussex University on 9th December 2013
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Transcript of The Cosmic Web - Evening Lecture at Sussex University on 9th December 2013
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THE COSMIC WEBThe Cosmic
Web
BLOG: http://telescoper.wordpress.com
Peter Coles
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The Hubble Expansion
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2dFGRS
UDS
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THE COSMIC WEB
The Cosmic Web of Ideas
Dark matter
Dark Energy
The Big Bang
Cosmic Inflation
General Relativity
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THE COSMIC WEB
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The Stretching of Light!
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The Cosmic Microwave Background
• Discovered by accident by Penzias & Wilson (1965); Nobel Prize in 1978.
• Thermal (“black body”) radiation with a temperature about 3 degrees above absolute zero
• This radiation was produced when the Universe was 1000 times smaller, and 1000 times hotter
• The “Smoking Gun” of the Big Bang
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What put the Bang in Big Bang?
• A “bang” must involve sound waves…• These could have been generated
during the inflationary era by quantum processes
• These are random noise with a particular spectrum
• Gravity eventually turns these into galaxies and clusters of galaxies
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Planck Time!
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What put the Bang in Big Bang?
• If there was a “Big Bang” there must have been sound waves…
• These could have been generated in the very early Universe
• They started the process by which galaxies and stars eventually formed.
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The Big Bang theory is not complete!
• There are infinitely many possible big bang universes described by the same equations, but with different initial conditions.
• Some expand forever, some recollapse.• We have to use observations to pick
which of the big bang family is closest to our universe.
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Dark Matter…..
• Most of the matter in the Universe is dark..
• “Dark Matter” can be detected in galaxies and galaxy clusters.
• Observations suggest 00.25, not enough to close the Universe
• But the Universe appears flat...• ….and it is accelerating!
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Weighing Space
• As well as weighing individual objects, it is also possible to weigh the Universe as a whole
• To do this we need “standard rods” or “standard candles” which we view through curved space-time
• This can tell us about the curvature of space-time.
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Flat Space
Open Space
Closed Space
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Dark Energy
• The “Cosmological Constant” () was introduced by Einstein to make a static universe (his “biggest blunder”)
• Now we think of as “vacuum energy” that causes the expansion Universe to speed up..
• The vacuum energy is directly connected to the microscopic physics of elementary particles.
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fainter
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The Accelerating Universe
• Gravity pulls “normal” matter and energy; it doesn’t push.
• It is possible to engineer anti-gravity, but only with peculiar energy called “Vacuum Energy” or “Dark Energy”
• This is the idea behind inflation in the early Universe ..
• ..and possibly why the Universe accelerates now
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“CONCORDANCE”
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Precision Cosmology
“…as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns -- the ones we don't know we don't know.”