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The Beginning of Time

The Beginning of Time. Somewhere, something incredible is waiting to be known. - Carl Sagan. WHEN I heard the learn’d astronomer; When the proofs, the figures, were ranged in columns before me; When I was shown the charts and the diagrams, to add, divide, and measure them;

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The Beginning of Time

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  1. The Beginning of Time

  2. Somewhere, something incredible is waiting to be known. - Carl Sagan

  3. WHEN I heard the learn’d astronomer; When the proofs, the figures, were ranged in columns before me; When I was shown the charts and the diagrams, to add, divide, and measure them; When I, sitting, heard the astronomer, where he lectured with much applause in the lecture-room, How soon, unaccountable, I became tired and sick; Till rising and gliding out, I wander’d off by myself, In the mystical moist night-air, and from time to time, Look’d up in perfect silence at the stars.

  4. WHAT DO YOU THINK? • Did the universe have a beginning? • Into what is the universe expanding? • Will the universe last forever? • Are there other universes? • Can we ever find out what started everything? • Should we try??

  5. In this chapter you will discover… • Cosmology, which seeks to explain how the universe began, how it evolves, and its fate Um… not COSMETOLOGY…

  6. In this chapter you will discover… • Cosmology, which seeks to explain how the universe began, how it evolves, and its fate • The best theory that we have for the evolution of the universe—the Big Bang • How astronomers trace the emergence of matter and the formation of galaxies

  7. Key Essay Questions • How did the universe begin? • How will it end? • How do we know? What evidence do we have?

  8. Facts Must be explained by a scientific theory to be considered • Quasars more prevalent far away; we don’t see them beyond ~ 13 Billion light years.

  9. Facts Must be explained by a scientific theory to be considered • Cosmic Microwave Background Radiation

  10. Facts Must be explained by a scientific theory to be considered • The Night Sky is Dark (Olber’s Paradox)

  11. Olber’s Paradox – Why is the Night Sky Dark? • Ifthe universe contains an infinite number of stars, uniformly distributed in space, and the universe is infinitely old, then:

  12. Olber’s Paradox – Why is the Night Sky Dark? • Ifthe universe contains an infinite number of stars, uniformly distributed in space, and the universe is infinitely old, then: • Overall brightness received in any direction from those stars is constant. • Farther away, more space, but more stars in that space. • In every direction, eventually look at surface of a star, so…. • Every point in the sky should be as bright as the surface of a star.

  13. Olber’s Paradox If…then logical argument assumption conclusion Clearly the night sky IS dark The conclusion is false so one or more assumptions must be incorrect! The universe is not infinite in size, and not infinite in age!

  14. Facts Must be explained by a scientific theory to be considered • Hubble’s Law: Distant Galaxies move away from us, faster. The Universe is changing in time.

  15. Facts Must be explained by a scientific theory to be considered • 90% of the Universe is Hydrogen, 10% is Helium

  16. Facts Must be explained by a scientific theory to be considered • Quasars more prevalent far away; we don’t see them beyond ~ 13 Billion light years. • Cosmic Microwave Background Radiation • The Night Sky is Dark (Olber’s Paradox) • Hubble’s Law: Distant Galaxies move away from us, faster. The Universe is changing in time. • 90% of the Universe is Hydrogen, 10% is Helium

  17. Penzias & Wilson’s Horn Antenna used to discover CMBR

  18. WMAP satellite (2001)

  19. Boomerang Balloon-Lofted Probe above Antarctica (1998 & 2003)

  20. What is the Cosmic Microwave Background? • Relic “heat” energy from Big Bang • Released ~ 1/2 million years after Bang

  21. What is the Cosmic Microwave Background? • Before ~ ½ million years, universe was a “sea” of high energy particles & photons • After, universe cools, allowing neutral matter to form

  22. What is the Cosmic Microwave Background? • Radiation then is visible through space • Redshifted as universe expands

  23. Facts Must be explained by a scientific theory to be considered • The Night Sky is Dark (Olber’s Paradox) • Hubble’s Law: Distant Galaxies move away from us, faster. The Universe is changing in time. • 90% of the Universe is Hydrogen, 10% is Helium • Cosmic Microwave Background Radiation • Quasars more prevalent far away; we don’t see them beyond ~ 13 Billion light years.

  24. Assumptions • Physics: The laws we know of around us work everywhere in the same way. • Isotropy: The Universe looks the same as it appears to us – everywhere • Homogeneity: The Universe is made of the same stuff we see around us - everywhere

  25. Facts + Assumptions Theory • The Big Bang Theory • The universe started ~ 14 Billion years ago • All energy, incredibly hot and dense • Expands incredibly fast (inflation) • Matter (protons, electrons, neutrons) created from energy (E = mc2)

  26. Facts + Assumptions Theory • The Big Bang Theory • Some protons (Hydrogen) fuse to create Helium • Universe cools and expands • Eventually, neutral atoms form… • “Recombination” era is when CBR can be seen

  27. A Big Bang Timeline…

  28. A Scientific Story… • What would the universe have been like in the first few … • billionths of billionths of a second? • Seconds? • Three Minutes? • Why did the universe expand so quickly? • When did galaxies form? • Why did galaxies form?

  29. Most distant quasars & galaxies observed from time when Universe was ~ 1 billion years old. Cosmic microwave background is earliest light available (~400,000 years after Big Bang) How to know conditions at beginning of time? Conditions in the Early Universe

  30. Conditions in the Early Universe • Know forces, conditions & expansion rate of Universe today. • Run expansion backwards, model early universe!

  31. Running the film backwards…. • Today: FOUR forces seen in nature • Gravity (longest distance, weakest force)

  32. Running the film backwards…. • Today: FOUR forces seen in nature • Gravity (longest distance, weakest force) • Electromagnetic (light!)

  33. Running the film backwards…. • Today: FOUR forces seen in nature • Gravity (longest distance, weakest force) • Electromagnetic (light!) • Weak (radioactive decay, neutron decay)

  34. Running the film backwards…. • Today: FOUR forces seen in nature • Gravity (longest distance, weakest force) • Electromagnetic (light!) • Weak (radioactive decay, neutron decay) • Strong (“nuclear glue force”)

  35. Running the film backwards…. • Today: Successfully created tests conditions in lab to linkElectromagnetic, Weak, Strong forces • “The Grand Unified Theory” • We hypothesize that allfour natural forces were unified during VERY early universe

  36. Planck Era (t < 10–43 sec) (small details about) The Big Bang

  37. “Planck Era” (t < 10–43 sec) (small details about) The Big Bang • We are as yet unable to link…quantum mechanics & general relativity • We are still trying to describe what happened in this era with the LHC!

  38. GUT Era (10–43 < t < 10–38 sec) (small details about) The Big Bang • The Universe contained two natural forces: • Gravity • Grand Unified Theory (GUT) force electromagnetic + strong + weak forces unified

  39. GUT Era (10–43 < t < 10–38 sec) (small details about) The Big Bang • Lasted until Universe was 10–38 sec old. • “cooled” to 1029 K • strong force emerges separate and distinct from electro-weak force • energy released by this caused a sudden and dramatic inflation of the size of the Universe

  40. Electroweak Era (small details about) The Big Bang

  41. Universe contained three natural forces: gravity, strong, & electroweak Lasted until Universe was 10–10 sec old. Now “cooled” to 1015 K electromagnetic & weak forces separated Electroweak Era (10–38 < t < 10–10 sec) (small details about) The Big Bang

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