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The Cosmic Web - Evening Lecture at Sussex University on 9th December 2013
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The Cosmic Web - Evening Lecture at Sussex University on 9th December 2013

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The lecture focusses on the large-scale structure of the Universe and the ideas that physicists are weaving together to explain how it came to be the way it is. Over the last few decades, astronomers …

The lecture focusses on the large-scale structure of the Universe and the ideas that physicists are weaving together to explain how it came to be the way it is. Over the last few decades, astronomers have revealed that our cosmos is not only vast in scale – at least 14 billion light years in radius – but also exceedingly complex, with galaxies and clusters of galaxies linked together in immense chains and sheets, surrounding giant voids of (apparently) empty space.

Cosmologists have developed theoretical explanations for its origin that involve such exotic concepts as ‘dark matter’ and ‘cosmic inflation’, producing a cosmic web of ideas that is, in some ways, as rich and fascinating as the Universe itself.

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Transcript

  • 1. TheCOSMIC WEB Cosmic THE Web Peter Coles BLOG: http://telescoper.wordpress.com
  • 2. The Hubble Expansion
  • 3. DS U 2dFGRS
  • 4. The Cosmic Web of Ideas DarkTHE matter COSMIC WEB Dark Energy The Big Bang Cosmic Inflation General Relativity
  • 5. THE COSMIC WEB
  • 6. The Stretching of Light!
  • 7. 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
  • 8. 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
  • 9. Planck Time!
  • 10. 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.
  • 11. 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.
  • 12. Dark Matter….. • Most of the matter in the Universe is dark.. • “Dark Matter” can be detected in galaxies and galaxy clusters. • Observations suggest Ω0≈0.25, not enough to close the Universe • But the Universe appears flat... • ….and it is accelerating!
  • 13. 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.
  • 14. Flat Space Open Space Closed Space
  • 15. Dark Energy • The “Cosmological Constant” (Λ) was introduced by Einstein to make a static universe (his “biggest blunder”) • Now we think of Λ as “vacuum energy” that causes the expansion Universe to speed up.. • The vacuum energy is directly connected to the microscopic physics of elementary particles.
  • 16. fainter
  • 17. 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
  • 18. “CONCORDANCE”
  • 19. 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.”