The document discusses key concepts in cosmology including the cosmic microwave background, dark matter, dark energy, and the accelerating expansion of the universe. It explains that the cosmic microwave background provides evidence for the big bang, while dark matter and dark energy help explain observations that cannot be accounted for by visible matter alone and suggest the universe is flat and accelerating in its expansion.

1. TheCOSMIC WEB
Cosmic
THE
Web
Peter Coles
BLOG: http://telescoper.wordpress.com

8. The Hubble Expansion

16. DS
U
2dFGRS

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

19. THE COSMIC WEB

20. The Stretching of Light!

25. 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

30. 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

34. Planck Time!

36. 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.

41. 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.

43. 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!

47. 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.

50. Flat Space
Open Space
Closed Space

53. 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.

55. fainter

56. 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

59. “CONCORDANCE”

61. 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.”