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Dark side ofthe_universe_public_29_september_2017_nazarbayev_shrt

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Dark side ofthe_universe_public_29_september_2017_nazarbayev_shrt

  1. 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. 2. Astronomy is oldest of all sciences…..
  3. 3. Nut, goddess of sky supported by Shu the god of air, and the earth god Geb.
  4. 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. 5. Seven Days of Creation "In the beginning God created the heavens and the earth"
  6. 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. 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. 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. 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. 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. 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. 12 Looking at Our Universe Solar System 160 light minutes
  13. 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. 14. •  Galaxy is derived from a Greek word which means milk.
  15. 15. Milky Way Galaxy 40,000 light years Looking at Our Universe 100,000 light years
  16. 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. 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. 18. People could also see some fuzzy objects in the sky. They called them Nebula, means cloud.
  19. 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. 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. 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. 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. 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. 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. 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. 26. HUDF, The total field of view represents only 1 ten millionth of the total sky
  27. 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. 28. Universe is Expanding Spacetime Galaxy
  29. 29. Universe is Expanding
  30. 30. Universe is Expanding Space itself is stretching!
  31. 31. 3131 Galaxies are observed to move away from us.
  32. 32. 3232 This is not galaxies moving through space (like a car on a road) but space itself expanding.
  33. 33. 3333 Observation ComputationTheory
  34. 34. 3434 We can learn about the universe and many things by looking at light beyond the visible.
  35. 35. 3535 The highest energy light has the shortest wavelength (gamma rays). Visible light is only a tiny portion of the entire spectrum.
  36. 36. 3636 X-ray Gamma Ray Optical (Visible)
  37. 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. 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. 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
  40. 40. 1964: Discovery of the Cosmic Microwave Background Signature of Big Bang! First Nobel Prize in Cosmology 1978, Arno Penzias and Robert Wilson
  41. 41. 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
  42. 42. 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
  43. 43. 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
  44. 44. 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!
  45. 45. 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
  46. 46. 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
  47. 47. Probes of Dark Matter (Indirect Evidences) •  Large Scale Structure and its Growth •  Expansion of the Universe •  CMB Anisotropy
  48. 48. The gravitational field of a galaxy (or cluster of galaxies) deflects passing light; the more mass, the greater deflection. Gravitational Lensing
  49. 49. Probes of Dark Matter (Indirect Evidences)
  50. 50. 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").
  51. 51. Probes of Dark Matter (Indirect Evidences)
  52. 52. 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.
  53. 53. Cosmological Observations Cosmic Microwave Background (CMB) Gravitational Lensing Type Ia Supernova Large-scale structure Lyman Alpha Forest Era of Precision Cosmology
  54. 54. 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.
  55. 55. 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
  56. 56. •  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:
  57. 57. 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
  58. 58. 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.
  59. 59. Eureka! or “What’s wrong with this?” Adam Riess’s notebook Fall 1997 Photo from R. Kirshner’s talk
  60. 60. Eureka! or “What’s wrong with this?” Adam Riess’s notebook Fall 1997 Photo from R. Kirshner’s talk
  61. 61. 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!
  62. 62. Photos from R. Kirshner’s talk
  63. 63. 65
  64. 64. 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.
  65. 65. 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.
  66. 66. 6868 STScI 95% of the universe is unknown! New Stuff Old New Stuff Us Us
  67. 67. 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
  68. 68. 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
  69. 69. 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
  70. 70. 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?!
  71. 71. 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
  72. 72. 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?
  73. 73. •  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.
  74. 74. 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
  75. 75. 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!
  76. 76. 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(?)?!)
  77. 77. 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,

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