1. DarkSide of the
UNIVERSE
Arman Shafieloo
Korea Astronomy and Space Science Institute (KASI)
& University of Science and Technology (UST)
ECL general seminar, 29 September 2017
Nazarbayev University, Astana, Kazakhstan

2. Astronomy is oldest of all
sciences…..

3. Nut, goddess of sky supported by Shu the god of air, and the earth god
Geb.

4. Old Testament Cosmology
Genesis 1:6-8New King James Version
(NKJV)
Then God said, “Let there be a
firmament in the midst of the
waters, and let it divide the waters
from the waters.” 7 Thus God made
the firmament, and divided the
waters which were under the
firmament from the waters which
were above the firmament; and it
was so. 8 And God called the
firmament Heaven. So the evening
and the morning were the second
day.

5. Seven Days of Creation
"In the beginning God created the heavens and the earth"

6. 66
What did we know about the
Universe in mid 18th century?
There are Sun, moon, planets, few moons of
big planets, lots of stars and constellations,
nebulas (some fuzzy object) and milky way
galaxy.
DATA IS INFORMATION AND INFORMATION CAN
BRING KNOWLEDGE

7. Looking at the sky, you see many fixed
stars and some stars which are moving
from night to night. These wandering
bright objects were called planets.
Movement of planet Mars from August 2007 to April 2008

8. Looking at the sky, you see many fixed
stars and some stars which are moving
from night to night. These wandering
bright objects were called planets.
Detecting Anomalies
Epicycles could not explain the data well

9. Observing the night sky helped us
to understand the solar system.
To explain the movements of the
planets we had to put the sun at
the center.

10. Observing the night sky helped us
to understand the solar system.
To explain the movements of the
planets we had to put the sun at
the center.
Modeling the Universe
to Explain the Data

11. 1111
Giordano Bruno 1548-1600
Martyr of Science
Campo de' Fiori, Rome.
Times that it was not much fun
to be a visionary scientist!

12. 12
Looking at Our Universe
Solar System
160 light minutes

13. Milky way by naked
eye in a clear night
sky away from cities.
How many of you
has ever seen milky
way in the sky?

14. • Galaxy is derived from a Greek word which
means milk.

15. Milky Way Galaxy
40,000 light years
Looking at Our Universe
100,000 light years

16. • We live at the outskirts of a huge, disk-like
collection of stars, the Milky Way Galaxy.
The Milky Way contains about
400,000,000,000 stars!

17. • We live at the outskirts of a huge, disk-like
collection of stars, the Milky Way Galaxy.
The Milky Way contains about
400,000,000,000 stars!
It is like number of hair on heads of 4,000,000
people! More than hairs on heads of everyone in
Astana, Almaty, Shymkent and Karaganda all
together!

18. People could also
see some fuzzy
objects in the sky.
They called them
Nebula, means
cloud.

19. People could also
see some fuzzy
objects in the sky.
They called them
Nebula, means
cloud.
Andromeda
(M31) by
naked eye.
Abd al-Rahman Sufi
described it as a “small
astronomical cloud” in
his Book of Fixed Stars
around 964 AD.

20. Technological
advancements
enabled us to
look more deep
in the sky.
Sir William
Herschel(1738-1822)
spent most of his life
on either building
bigger and bigger
telescopes or looking
at the sky.
In 1781 Herschel discovered Uranus
48 Incher
telescope-1789

21. Using the 48 incher telescope
William Herschel and his sister
Caroline, compiled the first
catalogue of northern nebulae.
48 Incher
telescope-1789
“General catalogue of
Nebulae and clusters
of stars”
Produced by John
Herschel in 1864
included more that 5000
entries.

22. 22
In 1908, Henrietta Swan Leavitt,
In 1908, Henrietta Swan Leavitt,
found a relationship between the
period (frequency of
pulsation)and luminosity of
Cepheid variables.
She found that they are
standard candles
Measuring Distances in Astronomy

23. Arrival of new technologies:
Spectroscopy and
Bigger Telescopes
In 1923 Edwin Hubble by using a 100 inch
telescope discovered that Cepheid variables
in Andromeda are much much dimmer than
those in Milky way. What does it mean?
Picture of
andrmeda

24. Arrival of new technologies:
Spectroscopy and
Bigger Telescopes
In 1923 Edwin Hubble by using a 100 inch
telescope discovered that Cepheid variables
in Andromeda are much much dimmer than
those in Milky way. What does it mean?
Andromeda cannot be a cloud within the Milky Way,
Andromeda is a Galaxy by its own!
Picture of
andrmeda

25. HUDF, The total field of view represents only 1 ten millionth of the total sky
This is a great discovery
In fact all these nebulae are galaxies maybe
as big as our very own Milky Way galaxy.
We are not lonely in the universe. Not
only there are around 400,000,000,000
other stars in our own galaxy, but there
are also millions and millions of
galaxies in the universe.

26. HUDF, The total field of view represents only 1 ten millionth of the total sky

27. In 1929 Edwin Hubble
observed that the further
away a galaxy is, the
more rapidly it is moving
away from us.
THE UNIVERSE
IS EXPANDING
First Hubble diagram, 1929
Another Great Discovery

28. Universe is Expanding
Spacetime
Galaxy

29. Universe is Expanding

30. Universe is Expanding
Space itself is stretching!

31. 3131
Galaxies are observed to move away from us.

32. 3232
This is not galaxies moving through space (like a
car on a road)
but space itself expanding.

33. 3333
Observation ComputationTheory

34. 3434
We can learn about the universe and many things
by looking at light beyond the visible.

35. 3535
The highest energy
light has the shortest
wavelength (gamma
rays).
Visible light is only a
tiny portion of the
entire spectrum.

36. 3636
X-ray Gamma Ray
Optical (Visible)

37. The distribution of matter in the universe on sufficiently
large scales is pretty much the same everywhere.
2DF Galaxy Redshift Survey
Observing the Universe

38. So…..
The universe is look like a uniformly
distributed collection of galaxies filed by
stars, gas and dust.
The universe is expanding, so initially it
must have been hot and dense!
Hot Big Bang Model!

39. Hot Big Bang Theory
• Based on General Theory of Relativity
• The universe on large scales is
homogeneous and isotropic ;
Robertson-Walker metric
• Friedman equations and expanding
universe
• Nucleosynthesis, abundance of light
elements.
• Cosmic Microwave Background Radiation

42. 1964:
Discovery of the Cosmic Microwave Background
Signature of Big Bang!
First Nobel Prize in
Cosmology
1978, Arno Penzias
and Robert Wilson

43. Is everything alright?
Anomalies in the rotational speed of galaxies.
The rotational curve of galaxies are not
consistence with the amount of matter in those
galaxies.
Structure formation. With this amount of matter
which we observe, structure formation should
have been much much slower!
Observing the Universe

44. We need another kind of matter, which
interacts only trough the force of gravity
and does not emit or absorb radiation.
DARK
MATTER
Fritz Zwicky 1933

45. 4545
This is called the galaxy rotation curve – how fast
stars move depending on their distance from the
center.
More mass as
radius increases
Beyond most of the mass so
gravity pull stops increasing
Gravity pull weaker at
large distances

46. 4646
But what we actually observe is very different!
Velocities, and the pull of gravity, stay strong at
large distances. There must be mass beyond the
mass we see!

47. 4747
But what we actually observe is very different!
Velocities, and the pull of gravity, stay strong at
large distances. There must be mass beyond the
mass we see!
DARK
MATTER

48. Probes of Gravitational wells
(Observational Evidences)
• Studies of the dynamics of stars in the local disk
environment
• Rotation curves for a large number of spiral
galaxies
• Approaching of Milky Way and Andromeda
(M31) to each other at a much faster pace than
can be explained by gravitation of the visible
mass.
• Extended X-Ray emission from many clusters of
galaxies
• Gravitational lensing

49. Probes of Dark Matter
(Indirect Evidences)
• Large Scale Structure and its Growth
• Expansion of the Universe
• CMB Anisotropy

50. The gravitational field of a galaxy (or cluster of galaxies)
deflects passing light; the more mass, the greater deflection.
Gravitational Lensing

51. Probes of Dark Matter
(Indirect Evidences)

52. Dark Matter Candidates
• Non-baryonic Dark Matter (axion, WIMP, …)
Cold Dark Matter
Hot Dark Matter
SUSY provides a symmetry between fermions and bosons. In SUSY, all
known particles have their super partners. Neutralinos, the lightest super
partners of gauge bosons , are the strongest WIMP candidate because they
hardly interact and are stable.
• Baryonic Dark Matter
Depending on their respective masses and speeds. CDM
candidates travel at slow speeds (hence "cold") or have
little pressure, while HDM candidates move rapidly
(hence "hot").

53. Probes of Dark Matter
(Indirect Evidences)

54. However,
• The nature of DARK MATTER is still unknown.
• Dark Matter can be consist of many different
candidates.
• At the present there are some efforts going on to
detect dark matter directly, nothing yet!
• But we are almost sure that there SOMETHING
EXIST!
• Different observations suggest that the amount
of dark matter should be around 5 to 10 times
more than the baryonic matter.

55. Cosmological
Observations
Cosmic Microwave
Background (CMB)
Gravitational Lensing
Type Ia Supernova
Large-scale structure
Lyman Alpha Forest
Era of Precision Cosmology

56. 5656
These very faint hotter and colder
spots came from the patches of
less dense and more dense
energy in the early universe (end
of inflation).
They also show the seeds of
matter structures that grew into
galaxies and clusters of galaxies.
The glow we detect everywhere in the sky is the
remnant glow of the early hot universe.

57. 1991, Map of the CMB
anisotropy by the
COBE spacecraft.
perfect fit for the black
body radiation from
COBE sattelite
George Smoot and John Mather,
received the Nobel Prize in
Physics in 2006

58. • CMB observations are very sensitive to
the curvature of the universe and baryon
density.
Curvature of the Universe is Flat
Early 2000,
BOOMERaNG and
MAXIMA CMB
observations
revealed:

59. Sensitivity of
the CMB
acoustic
temperature
spectrum to
four
fundamental
cosmological
parameters.
Total density
Dark Energy
Baryon
density and
Matter
density.
From Hu & Dodelson,
2002

60. Rising of another problem!!
• Mid 90’s: Indirect evidences were seen in the
distribution of the galaxies where Standard Cold
Dark Matter model could not explain the excess of
power at large scales.
• 1998: Direct evidence came by Supernovae Type
Ia Observations. Going to higher redshifts,
supernovae are fainter than expected. One can
NOT explain this by decelerating universe
suggested by SCDM.

61. Eureka! or
“What’s wrong with this?”
Adam Riess’s notebook
Fall 1997
Photo from R. Kirshner’s talk

62. Eureka! or
“What’s wrong with this?”
Adam Riess’s notebook
Fall 1997
Photo from R. Kirshner’s talk

63. Eureka! or
“What’s wrong with this?”
Adam Riess’s notebook
Fall 1997
Photos from R. Kirshner’s talk
2011: THIRD Nobel Prize in Cosmology
(Second in only 5 years)!
Accelerating Universe!

64. Photos from R. Kirshner’s talk

65. 65

66. Supernovae Ia Observations
• SN Ia are assumed to be a standard candles.
• By observing their apparent magnitude we can
calculate the luminosity distances at different
redshifts.
• Luminosity distances at a given redshift, for
different cosmological models are different.
• Luminosity distance is very sensitive to the
components of the total density.
• So we can use supernovae to distinguish between
cosmological models.

67. 6767
Beyond Einstein: What happens when gravity is
no longer an attractive force?
Scientific American
Discovery (SCP,HiZ 1998): 70% of the universe acts this way!
Fundamentally new physics. Cosmology is the key.

68. 6868
STScI
95% of the universe is unknown!
New Stuff
Old New
Stuff
Us
Us

69. Era of Precision Cosmology
Combining theoretical works with new measurements and
using statistical techniques to place sharp constraints on
cosmological models and their parameters.
Initial Conditions:
Form of the Primordial
Spectrum and Model of
Inflation and its Parameters
Dark Energy:
density, model
and parameters
Dark Matter:
density and
characteristics
Baryon density
Neutrino mass and
radiation density
Curvature of the Universe
Hubble Parameter and
the Rate of Expansion
Epoch of reionization

70. Dark Energy in 2017
18 years after discovery of the acceleration of the universe:
From 60 Supernovae Ia at cosmic distances, we now have ~800
published distances, with better precision, better accuracy, out to
z=1.75. Accelerating universe in proper concordance to the data.
SN
Union 2.1
Compilation

71. Dark Energy in 2017
18 years after discovery of the acceleration of the universe:
CMB directly points to acceleration. Didn’t even have acoustic
peak in 1998!
D. Sherwin et.al, PRL 2011
CMB
ACT CMB Survey

72. Dark Energy Models
• Cosmological Constant
• Quintessence and k-essence (scalar fields)
• Exotic matter (Chaplygin gas, phantom, etc.)
• Braneworlds (higher-dimensional theories)
• Modified Gravity
• …… But which one is really responsible for the
acceleration of the expanding universe?!

73. Reconstruction & Falsification
Reconstruction: Understanding the behavior
Falsification: Testing the Consistency
Initial Conditions:
Form of the Primordial
Spectrum and Model of
Inflation and its Parameters
Dark Energy:
density, model
and parameters
Dark Matter:
density and
characteristics
Baryon density
Neutrino mass and
radiation density
Curvature of the Universe
Hubble Parameter and
the Rate of Expansion
Epoch of reionization

74. Open issues on Dark Energy:
• Is dark energy really the cosmological constant?
Or its equation of state evolve by time?
• What is the nature of dark energy? Is it
geometrical or physical? it is the effect of higher
dimensions? What about the scalar fields?
• Can we relate dark energy and therefore the
acceleration in expansion of the universe to the
early acceleration of the universe, inflation?
• Any relation between mysterious dark energy
and mysterious dark matter?

75. • We need better quality of data to
distinguish accurately different models of
dark energy, however by any new set of
data, usually some cosmological models
are getting ruled out!
• We are moving toward the more accurate
precision cosmology. If we know the
behavior of dark energy, we can think
about its nature more confidently.

76. Is LCDM without any problem?
• Fine tuning problem
• Coincidence problem
The past was dominated by matter,
The future will be dominated by dark energy.
What makes the present day so special?
About 0.3 About 0.7

77. Conclusion (if any?!)
• We know many things, but still almost nothin.
100 years ago we had a nice cozy Universe,
now, something like 96% of different kinds are
missing, why?
• We can (will) describe the constituents and
pattern of the universe (soon). But still we do not
understand it. Next challenge is to move from
inventory to understanding, by the help of new
generation of experiments.
• We must be very happy! There are lots of
problems unsolved!

78. Some simple puzzles (time pass)
• Why there is more matter than anti-matter?
• What is dark matter?
• What is dark energy?
• Why the vacuum energy is so small?
• Where did the small fluctuations come from?
• Why matter and dark energy densities are
comparable today?
• What came before the big bang? (what was
GOD doing at that time(?)?!)

79. Behind physics is the more ancient and honorable
tradition of attempts to understand where the world
came from, where it is going, and why.
P. J. E. Peebles
My profession is to be forever journeying,
to travel about the Universe, so that I may
know all its conditions.
Abu Ali ibn Sina (Avicenna), 980-1037,