Study Points Give a brief timeline for the
Study Points • Give a brief timeline for the formation of the universe from Big Bang to present day (BB, first atoms, universe becomes transparent, first stars, galaxies, solar system, humans!) • What four pieces of observable evidence does the Big Bang predict? • Explain why we can observe the afterglow of the hot, early universe, and what the CMB tells us. • Is the expansion rate is accelerating? How do we know? What do we call that force? • Describe open, flat, and curved universes and explain which type of universe is supported by observations • Know basic properties of the universe including its age and contents (dark matter/dark energy/regular matter) • Explain why inflation is necessary to explain the universe we see today (Horizon Problem and Flatness Problem). • Name the four forces that control all physical processes in the universe
Evidence for the Big Bang
“The story so far: In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move. ” -- Douglas Adams, Hitchhiker’s Guide to the Galaxy
http: //www. neverofftopic. com/re-topics/science-year-10 -11/the-big-bang-theory/
Big Bang (BB) Timeline* • • • 10 -5 s: universe fills with sea of energy and particles 0. 0001 s: slight excess of matter over antimatter 4 s: protons, neutrons, electrons of today produced 3 min: He produced 30 min: Universe stops nuclear production 75% H & 25% He* 380, 000 yrs: Universe cools enough to become transparent* 200 -400 Myrs: first stars appear (H rich)* 1 -14 Byrs: Galaxies grow and Milky Way forms (~13 Byrs old)* Successive generations of stars enrich the next generation with heavier elements (massive stars) • 10 Byrs: Our solar system forms (~5 Byrs old)* • 14 Byrs: Humans think about the Universe!*
Creating Matter Energy makes particles & they make energy Universe cools enough for protons and neutrons to stick together Reionization: particles gain electrons
BIG BANG Inflation BIG BANG plus 10 -43 s Understand from here on Makes specific, testable predictions after 10 -43 s INFLATION Universe transparent Light from first stars Stars produce heavy elements BIG BANG plus 380, 000 years BIG BANG plus ~200 -400 million years BIG BANG plus 14 billion years
Approximate Size vs. Age of Universe The size of the Universe (y-axis, in light years) versus the age of the Universe (x-axis, in years) on logarithmic scales. Some size and time milestones are marked. https: //www. forbes. com/sites/startswithabang/2017/03/24/how-big-was-the-universe-at-the-moment-of-its-creation/#41 d 9 e 33 e 4 cea
Observable Evidence for BB 1. Redshift/Hubble’s Law – Universe began small and is expanding* 2. Specific testable results* a. H to He is 75% to 25% * b. First stars/galaxies at ~300 million years* 3. BB radiation found – CMB at 2. 73 K* 4. CMB is slightly lumpy – Planck Results* 5. Polarization of CMB – still looking
Evidence for BB* 1. Redshift – Universe began small* Hubble’s Law – Space-time expanding* • expanding at a faster rate accelerating
Time (~14 billion years) Universe Expansion Acceleration Due to Dark Energy ~5 Byrs ~9 Byrs http: //science. nasa. gov/astrophysics/focus-areas/what-is-dark-energy/ http: //www. scientificamerican. com/article/expanding-universe-slows-then-speeds/
Evidence for BB 2. Specific, testable prediction from Big Bang model a. H and He found at predicted 75% to 25% ratio* BB model predicts H and He fused from protons and neutrons in the first few minutes AND at 75% to 25% ratio by mass Found: 9 H to every 1 He (counting atoms) 75% of mass is H 25% of mass is He
Evidence for BB 2. Specific, testable prediction from Big Bang model b. Early galaxies BB model predicts: First star light should appear ~200 -400 Myears after BB* So far: 13. 4 Bly distant galaxy (~400 Myears after BB) Abell Galaxy Cluster From 2014 http: //news. nationalgeographic. com/news/2014/01/140107 -hubble-oldest-frontier-science-space-astronomy/
Evidence for BB 3. Radiation from BB predicted to be at 3 K Is 3 K hot or cool?
Evidence for BB 3. Radiation from BB predicted to be at 3 K Is 3 K hot or cool? Cool (-454 F)
*Evidence for BB 3. Radiation from BB predicted to be at 3 K Why so cool if universe began hot? If Universe began hot, what type of EM wave do we look for? First, what is the λ of red and violet? Microwave Electromagnetic spectrum? Wavelengths of red and violet?
*Evidence for BB 3. Radiation from BB predicted to be at 3 K Why so cool if universe began hot? If Universe began hot, what type of EM wave do we look for? λ of red = 700 nm & blue = 400 nm Microwave Electromagnetic spectrum? Wavelengths of red and violet?
*Evidence for BB 3. Radiation from BB predicted to be at 3 K Why so cool if universe began hot? If Universe began hot, what type of EM wave do we look for? Gamma rays Microwave
*Evidence for BB 3. Radiation from BB predicted to be at 3 K Why so cool if universe began hot? Universe expands for ~ 380, 000 years and cools to ~3000 K Now what would we see? Microwave
*Evidence for BB 3. Radiation from BB predicted to be at 3 K Why so cool if universe began hot? Universe expands for ~ 380, 000 years and cools to ~3000 K Would see IR! Microwave
*Evidence for BB 3. Radiation from BB predicted to be at 3 K Why so cool if universe began hot? After decoupling (380, 000 years after BB), Universe continues expanding, cooling, stretching the waves…. What EM type do we look for today? Microwave
*Evidence for BB 3. Radiation from BB predicted to be at 3 K Why so cool if universe began hot? After decoupling (380, 000 years after BB), Universe continues expanding, cooling, stretching the waves…. What EM type do we look for today? Microwaves Microwave
*Evidence for BB 3. Radiation from BB predicted to be at 3 K Found! Cosmic Microwave Background (CMB)
Arno Penzias and Robert Wilson in 1964 *Found Cosmic Microwave Background (CMB) *Universe is filled with radiation at 2. 73 K
*Evidence for BB 4. Tiny variations in CMB – Planck spacecraft results! • Radiation from the early universe is very smooth (2. 73 K) • Temperature of early universe does not vary much • Therefore density varies very little
*Planck Spacecraft Results* • Tiny variations in CMB (+/- 0. 0001 K) • Tiny temperature variations = tiny density variations in early universe ESA http: //www. esa. int/Our_Activities/Space_Science/Planck_reveals_an_almost_perfect_Universe
Evidence for BB: Planck results And early universe varied slightly in density from one spot to next => Seeds of galaxies. 0. 9, 3. 2, 13. 8 billion years after BB https: //imagine. gsfc. nasa. gov/news/17 dec 08. html
Evidence for BB 4. Planck results also show which BB model is correct. Different BB models predicted different sizes for these small variations and different ages for the universe.
Evidence for BB *4. More Planck Results Composition of Universe* • ~5% (4. 9%) “normal” matter – p, n, H, He, you; called baryonic matter • ~25% (26. 8%) dark matter • ~70% (68. 3%) dark energy (more in a bit)
Evidence for BB 4. More Planck Results (not for test) Data fits the accepted BB model very nicely except • Slight asymmetry in temperature variation from one side of universe to the other • “Large” “cool” spot (blue area near center)
Evidence for BB 5. Polarization (not on test) – specifically evidence for inflation (inflation coming up in a few slides) • Predicts CMB fluctuations that are tiny but measurable: polarization of CMB • Scientists thought they had measured it in 2014 with BICEP 2 in Antarctica, but Planck later proved them incorrect. Story here • Still looking for proof. Watch Polarization Demo Video https: //www. youtube. com/watch? v=n. CAKQQjf. Ovk
Evidence for BB 1. Redshift/Hubble’s Law – Universe began small and is expanding* 2. Specific testable results* a. H to He is 75% to 25% * b. First stars/galaxies at ~300 million years* 3. BB radiation found – CMB at 2. 73 K* 4. CMB is slightly lumpy – Planck Results* 5. Polarization of CMB – still looking
*Big Bang Model (from last lecture) The Universe (space and time): • Springs into (tiny) existence ~ 13. 8 Byrs ago • For tiny fraction of a second, inflating rapidly • For first 9 Byrs, – Expanding, cooling – Rate of expansion slowing due to gravity • For last 5 Byrs, – Rate of expansion increasing due to dark energy
Universe Expansion is Accelerating* (speeding up) • *Supernova distances are farther away than expected (standard candles!) [1998] • *Rate of expansion of the Universe has increased over the last 5 Byrs • *Something is causing the universe to expand faster now • *Named Dark Energy – ~70% of universe Type 1 a Supernovae remnant
Dark Energy Possibilities (not on test) • NASA: “More is unknown than is known. ” • Property of space? • Cosmological Constant from Einstein in 1917? – Opposite of attractive gravity force – Anti-gravity force • Quintessence? – Field – Vacuum energy from space – Explains subatomic particle behavior • Something else? ? https: //science. nasa. gov/astrophysics/focus-areas/what-is-dark-energy
Dark Energy Summary We don’t know what it is. We just know what it does. (Speeds up the expansion of the universe. )
https: //www. spacetelescope. org/images/opo 9919 k/ Future of the Universe Expanding now. What is next? Is the Universe… Closed? Flat? Open? Red lines show future of our universe – but those lines may or may not be flat to start
Future of the Universe • Closed (sphere) – density > critical density – expands and then collapses (Big Crunch) – greater than 1 angular degree in temp. change • Open (saddle) • density < critical density • expands slowly • less than 1 angular degree temperature change • Flat (sheet) • density = critical density • expands forever • 1 angular degree temperature change
Future of the Universe http: //archive. ncsa. uiuc. edu/Cyberia/Cosmos/Images/Oscillation_lg. jpg
Future of the Universe What makes a universe “closed”? Mass Does the universe have enough? Not enough mass – even counting dark matter and Increasing Acceleration doesn’t fit closed expansion Not a Closed Universe http: //archive. ncsa. uiuc. edu/Cyberia/Cosmos/Images/Oscillation_lg. jpg
Future of the Universe What makes a universe “open”? Mass Does the universe have the right density? Too much mass & density to be open Not an Open Universe http: //archive. ncsa. uiuc. edu/Cyberia/Cosmos/Images/Oscillation_lg. jpg
Future of the Universe • Not closed • Because of increasing acceleration Our • And too small of mass, too low of density • Not open Universe is • And too much mass, too high of density Flat http: //archive. ncsa. uiuc. edu/Cyberia/Cosmos/Images/Oscillation_lg. jpg
Future of the Universe The density is at critical density The temperature fluctuations are about one degree in (angular) size. Universe is Flat (expanding indefinitely) http: //archive. ncsa. uiuc. edu/Cyberia/Cosmos/Images/Oscillation_lg. jpg
Cosmic Microwave Background • Small fluctuations in CMB
Fluctuations in the Cosmic Microwave Background • Angular size of the CMB fluctuations allows us to probe the geometry of space-time! • CMB fluctuations fit the FLAT MODEL universe best
NASA WMAP confirmed flatness in 2013 380, 000 years about 200 million years 13. 8 billion years http: //wmap. gsfc. nasa. gov/media/060915_CMB_Timeline 150. jpg
“Over time, gravitational interactions will turn a mostly uniform, equal-density Universe into one with large concentrations of matter and huge voids separating them. ” Image credit: Volker Springel. https: //www. forbes. com/sites/startswithabang/2017/02/24/cosmic-superclustersthe-universes-largest-structures-dont-actually-exist/#1 ccf 468 e 15 c 1
BIG Questions We’ve been dealing with some pretty big questions about the universe and our fate. • Form a group & discuss your personal reactions to discussing questions like the beginning of time and space, and the ultimate fate of the universe. • Are you more on the side of “we were not meant to know the answers” or are humans capable of exploring questions? • Does it make you nervous to hear about scientists discussing these issues? Or is it exciting to know that we can now gather scientific evidence about the origin and fate of the cosmos? • In discussing this, you may find that members of your group strongly disagree; be respectful of others’ points of view.
Standard Big Bang Model leaves some questions Much of the information after this point has not been observationally proven. Scientists answer questions as best we can, using the information available to us. New evidence may produce different theories in the future. This does not mean it’s “just a guess. ”
Standard Big Bang Model leaves some questions 1. Horizon Problem: How is the CMB the same temperature everywhere we look? These areas did not start off close enough to share a temperature, and the universe is not old enough for them to have “mixed” to form one temperature now. 2. Flatness Problem: Why is the universe flat? Even a tiny deviation from perfect flatness at the time of the Big Bang should have been amplified to a huge deviation today.
Solution to Horizon and Flatness Problems* Inflation: period of sudden expansion during the very early evolution of the Universe* --Alan Guth, 1979 Initially tiny (tinier) universe can exchange information so it looks the same everywhere now (horizon problem) Also solves the flatness problem
Inflation Astronomy, Andrew Fraknoi
Four Fundamental Forces – to understand inflation
Four Fundamental Forces* • Gravity* – holding us down • Electromagnetic* – magnets, static, electrons in orbit • Weak* – radioactive decay (change in P, N, or E) • Strong* – holds atomic nuclei together (protons & neutrons)
Inflation Predicts Four Forces Start as One Force http: //www. astro. upenn. edu/~trilling/teaching/spring 2003/lectures/lecture 9/s 10. html
Forces at the Beginning of Time Why four forces? • Maxwell united electricity and magnetism • Maybe the others used to be united as well • High temperature of early universe could have united them Gives rise to quantum gravity and string theory
More Questions About Our Universe Multiverse? Multi-universes? Megauniverse? Extra Dimensions? Parallel Universe? No Evidence – but fun to consider
More Questions About Our Universe Are we the only ones out there? Next lecture: Life in the Universe
Homework & Updates • Keep up with Study Points • D 2 L Quiz 9 -13 available; Quizzes 9 -13 for Test 3 • Optional – watch: • Dark Energy, Cosmology part 2: Crash Course Astronomy #43 • Ted Talk: The most mysterious star in the universe by Tabetha Boyajian • Try out Grade Calculator on class website • Tutor Oskar available in T bldg. room 3200 Optional – watch: • Observations: • Astronomy News Evalution Due Dec. 10 (20 pts) Evaluate astronomy news • Dark Energy, Cosmology part 2: Crash Course nd picture of sunset in same place • Sunset – Part 2 Due Dec. 10 (10 points) Take 2 Astronomy #43 • Take picture about 4 pm; sunsets about 4: 40 pm • Ted Talk: The most mysterious star in the universe by • Stargazing Due Dec. 17 (20 pts) Go stargazing & write report Tabetha Boyajian • Telescope Due Dec. 17 (20 pts) Look through a telescope • Look at calendar options & weather • Moon Craters Due Dec. 17 (10 pts) Look at magnified moon craters • Borrow binoculars from Lab room • Pick up lab notebooks and test today • Let Raquel know if you want to take optional Lab Test 2 on Dec. 10 or 12
Calendar Summary • Thursday, 12/5: Big Bang & pick up lab notebooks in lecture • Tuesday, 12/10: Life in the Universe (optional Lab Test 2) • Thursday, 12/12: Test 3 (60 multiple choice questions) – – Based on last 8 lectures & 5 D 2 L quizzes 9 -13 Some questions from D 2 L quizzes Bring pencil, no calculator needed Optional Lab Test 2 during lab time • Tuesday, 12/17: Final Test today & handback Test 3 – – – Based on all 23 lectures & 13 D 2 L quizzes (the whole semester) Many questions from D 2 L quizzes Bring pencil & calculator if you have one (some in classroom for you) Remember lowest of 4 tests is dropped (Test 1, 2, 3, & Final). If you took 3 previous tests and are happy with your grade, then you don’t have to take the Final Test. If you missed a previous test, you must take the Final Test. If you are trying to increase your grade, take the final to hopefully drop a different test. No Astronomy on 12/19.
- Slides: 60