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Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 25 & 26 Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 1 Prep for Today (Is now due) – L26 • Reading: – Required: BBBHNM: Chapter 20 • eLearning Quizzes: – Chapters 2-18 • Reading questions: – Two questions from Chapter 20 • Papers: – Paper 4 CPR due Wednesday at Noon – Paper 5 due one week after we finish Chapter 20 • NOT the last day of class Big Early Times & Fate of The Universe 2 Bang, Black Holes, No Math Topic 2: Dark Matter Course Evaluations This semester course evaluations will be done online "Department of Physics On-Line Course Evaluation System“ http://evaluation.tamu.edu/ Please, take a few minutes to fill these out. I really appreciate it! 3 Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter Unit 6 Going back in time and going forward in time Before the first millionth of a second and the Fate of the Universe Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 4 Outline of Unit 6 1.Possible Fates of the Universe Today 2.The Case for Dark Matter 3.Particle Physics and Dark Matter 4.Inflation 5.Dark Big Bang, Black Energy Early Times & Fate of The Universe 5 Holes, No Math Topic 2: Dark Matter Summarizing the Data so Far 1. Redshifts of Galaxies gives us the speed of expansion fairly accurately 2. The measured mass of the “stars and stuff” gives about 4% of the critical density 3. The Cosmic Background Radiation is consistent with a density of 100% of the critical density Something is inconsistent… Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 6 The Story There is a strong case to be made that there is Matter and Energy in the Universe we can’t “see” directly • The Evidence for Dark Matter – Today • Particle Physics and Dark Matter – The Standard Model and Supersymmetry – Next time Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 7 Today’s Lecture The Case for Dark Matter 1.The Rotation of Galaxies 2.Gravitational Lensing 3.Colliding Galaxies Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 8 What is Dark Matter and why do we call it Dark Matter? What do we see when we look at the Heavens? • Our eyes see photons, but with other detectors we can see electrons, protons, atoms and neutrinos • All these things interact with photons we can “see” them because they produce the light we observe Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 9 Dark Matter • If there is something else out there it must not interact with light very much • Call this “Dark Matter” Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 10 Evidence 1 Watch the way stars rotate around the center of Galaxies Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 11 The Planets and the Sun General Relativity does a good job of predicting the planets path around the sun assuming virtually all the mass of the Solar system is located at the Sun – Only small influence due to the small masses of the other planets Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 12 What about Stars and Galaxies? • Can again use General Relativity to predict the orbits of stars as they move around the galaxy • Should look like a complex collection of individual stars all in separate free orbits around the heart of the galaxy • Problem: This isn’t what the data shows Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 13 The Data Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 14 Does this work for Stars? Watch how fast a star rotates around the center of the galaxy… Simulation without Dark Matter Simulation with lots of Dark Matter particles in the galaxy Big Bang, Black Early Times & FateData of The Universe looks like this 15 Holes, No Math http://bigbang.physics.tamu.edu/Figures/StolenAnimations/galrot_anim.gif Topic 2: Dark Matter Stuff Outside the Stars? • Can also look at the clouds of hydrogen on the outskirts of the galaxy • Also rotating faster than they should be • Looks like they are feeling the gravity of a large amount of mass we can’t “see” Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 16 Dark Matter? Data well explained by lots of “Dark Matter” we can’t see Mostly clumped at the center due to gravity Lots of it in a “halo” around the entire galaxy Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 17 Evidence 2 Look at the gravitational impact on light that travels through the Universe towards us Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 18 General Relativity and Light • The large mass Is here “Looks” like of the Sun can its here bend the path of light • Result: The apparent position of a Light’s path in star “moved” as curved the light passed space time from outer space, past the Big Bang, and Black Early Times & Fate of The Universe Sun, to us 19 Holes, No Math Topic 2: Dark Matter Looking at Light from the Universe Galaxy Light from a Galaxy Hydrogen Another Galaxy Cloud Looks like a Galaxy Looks Lookslike likea aGalaxy Galaxy behind a cloud of heavy behind a cloud of “stuff” that isn’t just hydrogen stars and hydrogen Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 20 Lensing of Galaxies Prism • Dark Matter “Lenses” the galaxies behind them like a prism • Evidence that the light coming to us is passing through lots of matter we can’t see directly Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 21 More on Lensing Sometimes we can even see more than one image of the same galaxy! Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 22 Evidence 3 Colliding Clusters of Galaxies Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 23 Look at Colliding Clusters of Galaxies Atoms in the Galaxies interact and slow down as they pass through each other Atoms Atoms Dark Matter doesn’t interact much so it isn’t slowed down much Dark Matter Dark Matter Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 24 Colliding Galaxy Clusters The atom part and the Dark Matter part of Galaxies interact differently as they pass through each other Atoms and Dark Matter Atoms and Dark Matter Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 25 Colliding Galaxy Clusters Galaxy Galaxy Galaxy Light from a Galaxy Atoms and Dark Matter Atoms and Dark Matter Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 26 Evidence for This in Nature? Colliding Clusters of Galaxies Blue is the part from lensing only “Fast Dark Matter” Red part from observing the light “Slow Atoms” Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 27 http://bigbang.physics.tamu.edu/Figures/StolenAnimations/bullett_anim_lg.mpg Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 28 What IS Dark Matter? We don’t know… Still working on it… Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 29 Prep for Next Time – P25 • Reading – Required: BBBHNM Chapter 20 • Reading questions – Two questions from Chapter 20 • eLearning Quiz – If we finished Chapter 19 then end-ofchapter quiz 19 • Papers – Paper 3 revisions due Tuesday at noon if you want – Paper 4 due Wednesday at 11:55PM Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter Prep for Next Time – P26 • Reading – Required: BBBHNM Chapter 20 • Reading questions – Two questions from Chapter 20 • eLearning Quiz – If we finished Chapter 19 then end-ofchapter quiz 19 • Papers – Paper 4 CPR due Wednesday at Noon – Paper 5 due one week after we finish Chapter 20 Big Bang, Black the Earlylast Times & Fate The Universe • NOT day of ofclass Holes, No Math Topic 2: Dark Matter Full set of Readings So Far • Required: – BBBHNM: Chaps. 1-20 • Recommended: – TFTM: Chaps. 1-5 – BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-137), 12 – SHU: Chaps. 1-3, 4(77-86), 5(95114), 6-8 (up-to-page 164) – TOE: Chaps. 1-3 – Seeds (Cosmology in the 21st Century) Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 33 http://bigbang.physics.tamu.edu/Figures/StolenAnimations/dark_matter_lg.mpg Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 34 For Next Time Could the Dark Matter just be a bunch of a single type of new fundamental particle? • Chap 20: Particle Physics – The Standard Model of Particle Physics – Supersymmetry Full reading for Unit 6: • BBBHNM: Chaps. 18-22 • SHU: 8 (159-164) • BHOT: 11 (122-137), 12 • Seeds (Cosmology in the 21st Century, Web Handout) Full reading through Unit 6: • BBBHNM: Chaps. 1-22 • TFTM: Chaps. 1-5 • BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-137), 12 • SHU: Chaps. 1-3, 4(77-86), 5(95-114), 6-8 (up-to-page 164) • TOE: Chaps. 1-3 • Seeds (Cosmology in the 21st Century) Lecture prep: Turn in on eLearning Two questions from Chapter 20 you want to know the answer to Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 35 The Data Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 36 Papers • Paper 1 is done • Paper 2 grades are on eLearning – All grades fixed, revision paper grades posted • Paper 3: – We have fixed papers for calibration problems – Still mis-graded? Let us know! – Do CPR if you submitted a revision • Paper 4: – Was due today before class • Paper 5 (last paper, no final) – Assigned after we start Chap 20 Big Early Times & Fate of The Universe 37 Bang, Black Holes, No Math Topic 2: Dark Matter Other Stuff • Elearning: – Unit 5 has Unit 6 questions (sigh…) – 5 and 6 will both be due last day of class • Schedule from here on out – Today: Ch 19 & 20 (paper 4 due) – Wed Apr 21: No class, Muster – Mon Apr 26: Ch 20 &21 (paper 4 CPR due) – Wed Apr 28: Ch 21 & 22 – Mon May 3: Ch 22 (last day of class, paper 5 due) Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 38 The Reading for Unit 6 Full reading for Unit 6: • BBBHNM: Chaps. 18-22 • SHU: 8 (159-164) • BHOT: 11 (122-137), 12 • Seeds (Cosmology in the 21st Century, Web Handout) Full reading through Unit 6: • BBBHNM: Chaps. 1-22 • TFTM: Chaps. 1-5 • BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-137), 12 • SHU: Chaps. 1-3, 4(77-86), 5(95-114), 6-8 (upto-page 164) • TOE: Chaps. 1-3 • Seeds (Cosmology in the 21st Century) Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 39 Evolution of The Universe Put it all together and there is significant evidence that there is LOTS of dark matter in the Universe Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 40 Writing Assignments Short Assignments 1, 2 & 3 Re-do’s are still possible. Want to revise again? Talk to me eLearning: Unit 5 past due Need to be working on Unit 6 Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 41 Last Paper Due last day of class 1. If you did the Black Hole paper your paper is posted now, on Dark Matter 2. If you did not do the Black Hole paper you must turn in a Research Paper Turn in at eLearning like usual Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 42 Ok… What Does it Look Like? • Stars look more like they are turning as if they are part of a single solid, giant wheel • Looks like this wheel would be MUCH more massive than the sum of all the stars in the galaxy • Also, much more spread out than most of the mass at the center Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 43 Does this work for Stars? Watch how fast a star rotates around the center of the galaxy… http://bigbang.physics.tamu.edu/Figures/StolenAnimations/galrot_anim.gif Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 44 Evidence 4 • Is the universe made up of just the known particles? – Electrons? – Protons? – Neutrons? – Neutrinos? • Perhaps its just known particles we can’t see? – The Earth doesn’t shine… Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 45 Composed of Normal Matter? • Lots of “protons and neutrons” we can’t see? • Look at the amount of Deuterium and Lithium in the Universe • The data predict that normal matter is only ~4% of the critical density • Consistent with other observations Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 46 Does this work for Stars? Watch how fast a star rotates around the center of the galaxy… Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 47 Does this work for Stars? Watch how fast a star rotates around the center of the galaxy… Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 48 How the Earth looks to Light… Path doesn’t curve Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter Path does curve 49 What is the Evidence for Dark Matter? Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 50 • Need a picture here… • TCP Figure 21.1, page 614 ? • Shockwave video comparing galaxy rotation with and without dark matter Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 51 Dark Matter • Combined mass of all “visible” matter (i.e. emitting any kind of radiation) in the universe adds up to much less than the critical density. • Gravitational lensing shows that some clusters contain 10 times as much mass as is directly visible. Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 52 • From this we can conclude (but not prove) that much of our galaxy’s mass must lie beyond the distance of the Sun’s orbit around the galactic center, and distributed throughout the galaxy’s spherical halo • Most of the light comes from the center • Thus, there is a large amount of matter that we can’t see Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 53 Rotation Stuff • However, there is lots of “dark matter” that we cannot see directly but which we know must be there Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 54 SHU 8 cont… • This “dark, unseen matter must have so much mass that it held the stars in position, making them the shining hub of a giant invisible wheel” Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 55 TCP 21 • One of our favorite reasons is to look at the atomic hydrogen clouds in the Milky Way. • The clouds lay very far out from the galactic center (further out than our sun) and are rotating faster than they should be if they were just feeling the gravity of the mass we can “see” Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 56 • There had to be part of the galaxy which were just not seeing, and that this must make up far more of the total mass of the galaxy than the stars we could observe shining Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 57 Why do we believe? • Why do we believe there is other stuff out there that we can’t see? • Three reasons 1. The way stars rotate around the center of Galaxies 2. Look at the gravitational impact on light that travels through the Universe towards us 3. Colliding Galaxies Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 58 Two Topics We can use the evidence that we live in a Flat, Homogenous and Isotropic Universe as evidence for two main things 1. Other Mass/Energy in the Universe (This Time) 2. Inflation (Coming Soon) Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 59 • Evidence that we live in a Flat, Homogenous and Isotropic Universe and its implications • If we live in a flat Universe where is the rest of the Mass/Energy that makes up the rest of the “critical Density” • Missing Mass and Energy in the Universe and the case for Dark Matter Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 60 Outline • SHU 8 first part • TCP 21, but not really… Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 61 • “If you assumed that all the stars we can see in the galaxy are free to affect each other gravitationally in exactly the same way gravity governs the dynamics of the solar system, then our galaxy should rotate differently than we observe them to… Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 62 Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 63 Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 64 Baryonic Dark Matter Brightness of background star Nature of baryonic dark matter still very uncertain and speculative. One component: MAssive Compact Halo Objects = “MACHOs”: Time Small compact objects (e.g., brown dwarfs, small black holes) acting as gravitational lenses. Big Bang, Black Early Times & Fate of The Universe 65 Distant background star Holes, NoEarth Math MACHO Topic 2: Dark Matter TCP 21 cont… • The universe has two possible fates: It might continue to expand forever, or it might someday stop expanding and begin to collapse • We don’t yet know the fate of the universe because the answer depends on the overall density of matter in the universe – and we cannot determine the overall density until we first determine how much dark matter is out there • Finished? Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 66 Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 67 • This is some text Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 68 Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 69 Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 70 Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 71 Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 72 • Dark unseen matter surrounding the galaxy like a halo Big Bang, Black Early Times & Fate of The Universe Holes, No Math Topic 2: Dark Matter 73