The document discusses key concepts in cosmology including the cosmic web, dark matter, dark energy, the Big Bang theory, and inflation. It summarizes Nobel Prize-winning discoveries like the cosmic microwave background and expanding universe. While observations support the standard model of cosmology, dark matter and dark energy remain largely unexplained. Future work aims to better understand the nature and distribution of matter and energy throughout the universe.

2. THE COSMIC WEBThe Cosmic
Web
Peter Coles
(@telescoper)

7. The Hubble Expansion

14. 2dFGRS

16. Nobel Prize for Physics
2019

18. THE COSMIC WEB
The Cosmic Web of Ideas
Dark
matter
Dark
Energy
The Big
Bang
Cosmic
Inflation
General
Relativity

19. THE COSMIC WEB

20. The Stretching of Light!

21. 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.

27. 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

32. 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

35. Nobel Prize for Physics
2006

44. Dark Matter…..
• Most of the matter in the Universe
is dark..
• “Dark Matter” can be detected in
galaxies and galaxy clusters.
• Observations suggest 00.25, not
enough to close the Universe
• But the Universe appears flat...
• ….and it is accelerating!

48. 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.

53. 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.

55. Nobel Prize for Physics
2011

57. fainter

59. Reasons for Dark Energy
• 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
• .

62. 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

63. 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.

64. TG 
Gravity Stuff

65. TG ?

66. ? TG

68. Alternatives
•Modified Gravity
•Back-reaction of structure
•Is Dark Energy Dynamical?
•None of the above….

70. “CONCORDANCE”

72. Conclusions
• The standard cosmology is a great
success, but we don’t know what
most of the Universe is made of.
• It is possible that we are thinking
about things the wrong way
entirely?
• The biggest problems now are
theoretical, not observational..

73. 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.”