Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 18 & 19

1. Big Bang, Black Holes, No MathASTR/PHYS 109Dr. David TobackLecture 18 & 19

2. Was due Today – L18 • Reading: • Unit 4 • Pre-Lecture Reading Questions: • Unit 3 Revision in CPR (if desired): Stage 2 • Unit 4: Stage 2 • End-of-Chapter Quizzes: • Chapter 12 • Papers: (Dates changed from last week) • Paper 2 Revision (if desired): • Stage 1 due Wednesday before class • Paper 3: • Stage 1 due Wednesday before class

3. Was due Today – L19 • Reading: • Unit 4 (will assign Unit 5 today) • Pre-Lecture Reading Questions: • Unit 4 Revision (if Desired): Stage 2 • Unit 5 (current guess): Stage 1 will be due Monday • End-of-Chapter Quizzes: • Chapter 12 • Papers: • Paper 2 Revision (if desired) • Stage 2 due Wednesday before class • Paper 3: • Stage 2 due Wednesday before class

4. Unit 4: Evolution of the Universe • Big Picture of the Evolution of the Universe: Temperature and Time • Collisions and how they explain what we see • The First Three Minutes • After the First Three Minutes

5. Getting Started We now have a basic understanding of the evidence for the Big Bang Lets look at the Origin and Evolution of the Universe

6. The Big Bang • Ideally we’d start telling the story at the Big Bang itself and then move forward • Maybe even talk about what came BEFORE the Big Bang • Unfortunately, we don’t REALLY understand the Bang part or if there even was a bang

7. Best We Can Do • The best we can do with confidence is start describing the Universe a short time AFTER its beginning • Start there, then work our way forward and backward in time What happened RIGHT AFTER the Big Bang? Then what happened after that? Then what? Etc.

8. The Big Bang Theory • A Big Bang occurs and the early Universe comes into thermal equilibrium with lots of high energy particles • Then the Universe gets • Bigger • Older and • Colder • As time goes by it changes over time • Often we use the word evolves

9. The History of the Universe 0 10 billion degrees 1 degree Universe cools down as time passes 1 second 10 billion years • Bigger wavelengths • Smaller energies • Smaller Temperature Universe expands as time passes

10. What happens at Different Times? Particles, nuclei and atoms interact in different ways at early times and later times • Early Times  High Temperature  High energy collisions • Later Times  Low Temperature  Low energy collisions

11. Various Times Explain what happens during each of a number of different periods in time • The VERY early universe • The first three Minutes • The next 300,000 years • The next billion years • ~13 billion years later (now) • The ultimate fate of the universe? • The first four will take a couple of lectures } Chap 13 } Chap 14 } Chaps 15-17 } Unit 6

12. What Happening? What happens to the particles at each of these times? Collisions!

13. Collisions In each collision a number of things can happen • Can create new particles • Only in high energy collisions • Particles can combine to form composite objects • Protons, neutrons, atoms etc. • Composite particles can get broken up • Collisions can transfer energy Thus, the energy of the particles and what particles CAN exist in nature has a HUGE impact on the evolution of the early universe Should also say that particles can decay

14. A Brief History of Time • The Big Bang (?) • Universe comes into Thermal Equilibrium • Quarks and gluons combine to form protons and neutrons • Protons and Neutrons combine to form deuterium and helium nuclei • Protons and electrons combine to form hydrogen atoms • Stars and galaxies begin to form • Our solar system forms • You take ASTR/PHYS 109 • Zero • Well before a trillionth of a second • One millionth of one second • A few minutes • A few hundred thousand years • 100 million to 1 billion years • 9 billion years • ~13.5 billion years

15. More detail

16. Confidence in this Story? • How do we know this is what happened back then? • What is the evidence for it? • Will walk through the reasons next… It’s all about the energy of the collisions…

17. The Evolution of the Universe Overview • The Early Universe • The First Three Minutes • The next 300,000 years • The next billion years • The next ~13 billion years, until today The particles have the same temperature everywhere • Once the Universe comes into Thermal Equilibrium, it doesn’t really depend too much on what came before it

18. Not exactly sure how it all starts… Call it a Big Bang Artists conception…

19. Before a Millionth of a Second Lots of free particles at VERY high energies • Quarks • Photons • Electrons • Others Back when the Universe was very small it quickly came into Thermal Equilibrium

20. Before a millionth of a Second Lots of free particles, all with the same temperature…

21. Quarks can combine in the Early Universe to make a proton, but are quickly broken apart by high energy photons in the Universe qqq  Proton Photon + Proton  qqq Quark Nuclear Reaction Proton High Energy Photon Quark Quark

22. Particles in the Universe: The Bathtub analogy Before a millionth of a second  very high energy collisions • Lots of free quarks to make protons • Not many protons in the Universe because they are quickly busted apart Protons-in-The-Early-Universe Bathtub

23. Time passes • The Universe Expands and Cools • Our story starts at a millionth of a second after the Big Bang • Cool enough that when quarks combine to form a proton or neutron they stay together • Said differently, other particles aren’t energetic enough to bust them apart

24. A Millionth of a Second after the Big Bang The quarks have combined to form Protons and Neutrons

25. The Evolving Universe The Universe changes from this to this Early Universe Later Times

26. Protons after a Millionth of a Sceond After a millionth of a second • No more free quarks to make more protons • Number of protons doesn’t decrease because they aren’t getting busted apart by high energy photons • Don’t exist

27. Very Early Universe is Still Very Complicated • The other fundamental and composite particles also have a big impact • One example is a Muon which is (for our purposes) just a heavier version of an electron • Discuss them more in Chapter 19

28. Photons and Muons At very high energies photons can also turn into Muon pairs + - Muon pairs can turn into Photons + -

29. Muons are an Important Part of the Early Universe 0 Electron Anti-Electron Photon Muon Anti-Muon Muon pairs can always produce photon pairs If the photons are energetic enough they can interact and create muon pairs (or vice versa)  muons, electrons and photons all have the same temperature

30. Why Aren’t They Around anymore? • Most particles, except protons, electrons and photons decay REALLY quickly • Some at 10-24 sec, some 10-10 sec • Muons can live for 10-6 sec • Can study lots of different types of particles here in experiments on Earth • Need an accelerator to produce most new ones if you want to study them • The photons in Today’s Universe aren’t energetic enough to produce new ones

31. Muons can also decay Electron - Neutrino Muon - Neutrino

32. Muons in the Universe Early Universe Later Times

33. Very Early Universe is Very Complicated What particles CAN exist determine what’s going on in the Very Early Universe Problem: We don’t know if we have discovered all the fundamental particles yet! • Good reasons to believe there are new ones out that we just haven’t found yet • Need bigger accelerators and/or Other tools • More on this later also

34. Nuclei in the Early Universe Proton Proton + Proton  Deuterium Deuterium + Photon  Proton + Neutron Nuclear Reaction Deuterium A high energy photon can break apart the Nucleus before it can find an electron to create an Atom or find another nucleon to form a bigger nucleus High Energy Photon Proton

35. What’s happening at about a millionth of a second after the Bang? • Lots of protons • photons can’t break them apart any more • Not many heavy nuclei: every time one forms a photon busts it apart • Not many atoms: every time one forms a photon busts it apart • Few “fancy” particles since most would have decayed already, new ones not being produced

36. Moving towards later times… • Universe gets bigger, older and colder • By one hundredth of a second after the Big Bang there are basically no fancy particles left and the story is simpler to tell • Protons, Neutrons, Electrons, Photons etc.

37. Where are we? Fancy particles gone by this time

38. Photons and Electrons at Later Times 0 Electron Positron Low Energy photon Electron pairs and interact and annihilate but photon pairs no longer turn into particle pairs No easy way to produce more positrons

39. Approaching the Three Minute Mark • By three minutes after the bang the Universe is cool enough for Helium nuclei to form (4He) even though it doesn’t happen too much… • Complicated to produce 4He, lots of intermediate steps that are easier to break apart

40. Nuclei at Lower Temperatures Proton Nuclear Reaction Deuterium At these lower energies the photon can’t often break apart the Nucleus  Amount of Deuterium in the Universe rises Photon Proton

41. For Next Time– L18 • Reading: • Unit 4, will assign Unit 5 Next Time • Pre-Lecture Reading Questions: • Unit 4 Revision (if Desired): Stage 1 Due Wednesday before class • Unit 5 (current guess): Stage 1 due Monday before class • End-of-Chapter Quizzes: • Chapter 13 (if we finished Chapter 13, else just 12) • Papers: (Dates changed from last week) • Paper 2 Revision (if desired): • Stage 1 Due Wednesday before class • Paper 3: • Stage 1 due Wednesday before class

42. End of Lecture

43. 1 Paragraph Essay Question Why are there so many more hydrogen and helium atoms in the universe than any other type of atom?

44. Clicker Question Why is hydrogen the most abundant element in the universe today? • It is the lightest element • Any heavy elements that might have been present would have been broken apart by high energy photons in the early universe • Both of these contribute

45. Clicker Question Why do the photons in the universe appear to be in thermal equilibrium? • Because they all have exactly the same energy • They are in thermal equilibrium • The universe has the same temperature in all directions, and the photons are just one of the particles in the Universe

46. Clicker Question If the universe were contracting, which of the following would be evidence for it? • Distant galaxies would be less red-shifted • The Cosmic Background Radiation would have a lower temperature • Distant galaxies would be blue shifted • The Earth would be getting closer to the Sun • Atoms would start shrinking

47. Clicker Question Q: Which of the following statements is MOST correct? • The photons in the cosmic background radiation are there because the Universe has been expanding for ~13 billion years • The photons in the cosmic background radiation are there because the universe was in thermal equilibrium • The photons in the cosmic background radiation are there because photons can exist forever

48. For Next Time– L15 • Reading: • Unit 4 • Pre-Lecture Reading Questions: • Unit 3 Revision in CPR (if desired): Stage 1 • Unit 4: Stage 1 • End-of-Chapter Quizzes: • If we finished Chapter 12, then Chapter 12 (if not, Chapter 11) • Papers: • Paper 1 Revision (if desired): • Stage 2 due Monday March 17 by 11:55PM • Paper 2: • Stage 2 due Monday March 17 by 11:55PM • Paper 3: • If we finished Chapter 12, Stage 1 due Monday before class

49. Prep For Next Time – L19 • Note: May change depending on how far we get in lecture • Reading: • BBBHNM: All reading through Chapter 15 • Reading Questions: • All reading questions through 15 • End-of-Chapter Quizzes: • If we finished Chapter 13 then end-of-chapter quiz 13 (else just through Chapter 12)

50. Prep For Next Time – L20 • Note: May change depending on how far we get in lecture • Reading: • BBBHNM: All reading through Chapter 16 • Reading Questions: • All reading questions through 16 • End-of-Chapter Quizzes: • If we finished Chapter 13 then end-of-chapter quiz 13 (else just through Chapter 12)