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The Cosmic Web - Lincoln
The document discusses the cosmic web and cosmological concepts presented during the 1st Annual Robert Grosseteste Lecture. It covers topics such as the Big Bang, dark matter, dark energy, and the cosmic microwave background, highlighting the complexities and unknowns in understanding the universe. The lecture emphasizes that while standard cosmology is successful, significant gaps in knowledge remain, particularly regarding the composition of the universe.
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The Cosmic Web - Lincoln
- 1. THE COSMIC WEB TheCosmic Web 1st Annual Robert Grosseteste Lecture 23rd February 2017 Peter Coles
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- 19. THE COSMIC WEB TheCosmic Web of Ideas Dark matter Dark Energy The Big Bang Cosmic Inflation General Relativity
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- 21. The Stretching ofLight!
- 23. The Big Bangtheory 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.
- 28. 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
- 34. What put theBang 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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- 41. What put theBang 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.
- 48. Dark Matter….. • Mostof 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!
- 52. Weighing Space • Aswell 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.
- 57. 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.
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- 62. Nobel Prize forPhysics 2011
- 64. Reasons for DarkEnergy • Galaxies suggest dark matter is only 20 to 30% of what is needed to make space flat • The Cosmic Microwave Background tells us space is flat • Supernovae tell is that the Universe can’t be flat and dominated by dark matter • .
- 65. 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
- 66. 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.
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- 71. Alternatives •Modified Gravity •Back-reaction ofstructure •Is Dark Energy Dynamical? •None of the above….
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- 76. Conclusions • The standardcosmology is a great success, but we don’t know what most of the Universe is made of. • Maybe we are thinking about things the wrong way entirely • The biggest problems now are theoretical, not observational
- 77. Precision Cosmology “…as weknow, 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.”