1) Questions:a) Is the universe finite? i) That depends on how you set your parameters ii) It’s possible to have a model that is a finite Big Bangiii)It is possible to have one that is undefined(1)That’s what infinite means iv)He never looked into that part of the equation v) They usually define the universe as so dang big that you might as well call it infinite vi)We keep on discovering enormous quantities of more and more stuff vii) The rate of discovery is not slowing down (1)It is increasing viii) Any quote on the mass of the universe is junk ix)We don’t even know remotely enough to estimate the mass ofthe Universe x) Size: (1)Depends on meaning that you give to Universe (2)It is 13.7 billion years (a)You can’t see further than that (b)There hasn’t been more time for light to reach us (3)Doesn’t tell you how BIG the universe is, but what we can OBSERVE (4)Impossible to observe anything farther than the number of years since the big bang (a)Not enough time for the light to reach us (b)As far as we know, that statement is correct xi)Historian of Science impression: (1)Al Jolson 1930, “You ain’t seen nothing yet”xii) He’s followed/looked through old books (1)Have the very strong impression that we’re barely starting (2)There’s one scientist that said he had the impression that: (a)Universe is not only stranger than we understand, but stranger than we can understand xiii) Better than we were 10 years ago xiv) NOTE: Hold everything as tentative (1)There will be more textbooks (2)There will be improvements (3)It’ll make what we look at look primitive (4)Includes: Unit on cosmology xv) Remember: “A good faith rendering of the astronomy of the times” (1)You can’t criticize a person for doing what they can do (2)Can’t go beyond that (3)It’s a dare (4)Several of the things he’s taught us are wrong(a)Doesn’t know which ones or he wouldn’t have taught it wrong (b)He straight up says it might be wrong b) Different types/forms of nebula i) Types: (1)He conducted a formal history of science of that over the years that nebula became a large category subdivided (2)Never more than 7 at a time (3)They come up one by one as new things discovered that can’t fit into any categories (4)Scheme he was taught: (a)Nebulae are emission, reflection or absorption (i) He said this is junk because all three are all at the same time, just as different portions (ii) Different proportions, different wavelengths (b)Useful categorization: (i) Divide nebulae: 1. Pre-steller a. Proto2. Post-steller (ii) Gasses to gasses, dust to dust(iii) Take a nebula, condense & stir (iv) Advance: mostly hydrogen + helium, other stuff, not huge amounts 1. Goes through stars 2. Turns a lot of hydrogen into much heavier stuff (v) Death of stars splatters that stuff all over the universe including nebulae (vi) Nebulae results in star + result of star (vii) Star birth 1. Inbound (viii) Star death 1. Outbound (ix) Planetary nebulae 1. Worst name in all of astronomy 2. That’s what you get from a dead red giant 3. If you don’t have a dying red giant, go all the way to a supernova a. Supernova remnant i. Some are expanding nebulae (crab) ii. Inbound/condensed (pulsars/black holes) b. Can get a nebula from the outbound part of a supernova remnant i. Heavily enriched in nebulae heavier than helium ii. That’s how you spread them around(c) So many other categories have been used (i) Telescopes (ii) People who noticed cloudy splotches in the sky (iii) Could resolve into individual stars (iv) Proposition: all nebulae must be resolvable if you get a good enough telescope (v) Proven in 1800, some nebulae aren’t resolveable in the stars 1. Name: (silly) Nebulae properly so called a. Looks like a cloud and it isb. Category lasted for about 40-50 years in the 1800s (d)Category names come and go (i) Pre & post just fit the way (ii) Pre: planets still form (iii) Heavier elements come from supernova explosions and red giants (iv) Supernovae kick off fast 1. They’re from giant stars, they die fast2. There’s a substantial amount of enrichment from there 3. Let the gas of the Milky Way sit for 10 billion yearsa. Giant stars will flare and explode so that there is substantial enrichment (v) Post 1. Diffuse and join the general nebulousity (vi) A planetary nebula will dissipate in 50,000 years 1. Seeing faint things is improving faster than planetary nebula are dissipating 2. Telescopes improve: a. We will never lose sight of planetary nebula i. Though they are dissipating, our ability to recognize them will always be there c) Pulsars i) Safe distance ii) Concept behind them: iii)Are a kind of supernova remnant iv)A red giant that is not massive enough to go supernova, formsa white dwarf, not strong enough to overcome the forces that keep atoms apart v) Degenerate matter, it will not generate more energy vi)Will not form neutronsvii) Implosion of supernova: (1)When a core has turned to iron, all the stuff on the star slammed onto it(2)Confusion with everything on everything (3)Huge energy all at once (4)Crams electrons into protons (5)Overcomes the Pauli-Exclusion level that keeps electrons away from protons (6)Electrons crammed into protons give you neutrons (a)Particle physics guy would cringe viii) Complicated stuff happens fast and you end up with neutrons ix)Crammed together very much denser: x) White dwarf (1)Roughly size of Earth (tons per teaspoon)(2)Same thing into a city, it’s SF (10 km across) -> neutron stars (a)A billion tons per teaspoon (b)Incredibly dense, you could not survive its vincinity (3)Very intense magnetic fields (a)No reason to think that they don’t have strong magneticfields xi)Neutron stars: (1)Conservation of momentum + hot spot (2)Every time it spins in our view, we see a blip of light (3)Usually it’s radio, our radio telescopes pick this up (4)Pulsars… (a)The fastest one that he remembers rotates 642 times/sec (b)Very ultra-rapid rotation (c) Some are slower than 1 sec/revolution (d)He doesn’t remember a specific number of the slowest when he looked it up(i) Expected several seconds/revolution (5)They don’t understand neutron fluids (a)Can’t make in lab (b)Needs something stronger than H bomb (c) If you could do it, you couldn’t get a measurement out of (force of explosion would fuckup every instrument you have) (d)You can’t do that shit experimentally, the only stuff you have to go on are astronomers measuring pulsars (e)Everything is extrapolated