Galaxies
& Cosmology winter trimester 2012  2013 


syllabus
&
G&C
course expectations 

safety, tardy, classroom computer use, and honesty  
Astronomy
Picture
of the Day
what's up in the sky
this
week 
Monday, February 4, 2013 
February 5, 2013 
February 6, 2013 
February 7, 2013 
February 8, 2013 


butchered schedule block D meets: 8:35  9:05 am make sure you have the BUFF book project2people: do you want some part of tomorrow's lab period for project work? 
make sure
you have the BUFF book 
exams
begin 
project presentation schedule please be on time! it would be good if I had the copy of what you turn in while you are presenting, although it is not necessary reminder of project grading guidelines remember to include a worksharing statement if you are part of a group 

(always done before class) 
Big Bang, day 1: I prefer to think that we're starting at the moment of decoupling (the formation of the first atoms) and going backward in time (unfortunately the book is written forward in time, so you can jump backwards to about 1 second into the universe (i.e., after the Bang) and begin reading on page 729, starting on the last paragraph on the page, the one beginning with "Pair production ....) and continue through the end of 27(5) on page 732 you will also want to have turned to BUFF book page 44 (the one with the entire history of the universe on 5 different logscale axes) and be consulting it (to see if the events match those given in the book; some will correctly match; some will not... where are the mismatches?) 2project people can look below in the homework box to see what the 1project people are doing for homework (one that you should be capable of also) 
Big Bang, day 2: handout from yesterday's class & pp. 745  746: Cosmology gets graded: Making Sense of Modern Cosmology: how much of this stuff is likely to actually be true? (and therefore likely to be in the textbook in 10 years?) 
Big Bang, day 3 had not a good portion of the class been unable to describe what the cosmic background radiation is in coherent language, I would have assigned 26(8)... but there doesn't seem much point in doing that now.... you can read about the cosmic background again in section 26( 4, 5) 

things you should know the answer to before coming to class 
can you identify the 3 milestone "events" that occurred during the time period from 1 second to 15 minutes after the Big Bang? for each of these, what caused the "event" to start? what caused the "event" to end? we then want to use the cause of the event to then calculate what time (or temperature) this event began.... ("events" can last more than an instant; maybe they should be called "eras"?) and is the relationship between time and temperature the same during the Big Bang as it is now? and what is the one that applies to now anyway? (oh, wait, that's one of the homework questions for today) 
why did the 3 important events that we listed in class yesterday start? stop? how do we use each of these physics statements to calculate the time (or temperature) when each of these events start or end? (which have we already done earlier in the year?) 2 of the 3 are easy to describe and calculate... which is hard(er)? an old question with a new answer: what is the cosmic background radiation and where did it come from? 
the questions remain the same 

homework (written assignments to be turned in) 
for 1project people: consider the 5axisgraph on page 42?, buff book.... and let's consider "Size" the independent variable ("Size" r/r_{0 }for any galaxy) for each of the other axes, 1) state the physics law (or combination of laws) that relates this dependentvariable axis back to the independent variable axis & 2) give a numerical example (similar to the one I gave you in class concerning the temperaturesize relation) & 3) do some (or all) of the relationships change over the history of the universe? when do the change? why would that be? 


I forgot to remind you to put your conclusions from the galaxy collision lab into moodle (if you want credit for doing the lab, that is) 



of the week 
Decelerating American Science: US shuts down its last particle collider the Habitable Zone for planets around stars narrows: some exoplanets are kicked off the island of potential life Astrobites: each week an astronomy graduate student translate a research article into English for undergraduates why hasn't the whole universe collapsed into an enormous black hole? would your body clock be able to adapt to a 40minutelongerday on Mars? 
Monday, January 28 
January 29 
January 30 
January 31 
February 1 


make sure you have BUFF book with you for class today if everyone doing a second project has a project by today, I will let you use some or all of the lab time to work on project 2 
make sure you have BUFF book with you for class today what we did in "class" yesterday: 1) "found" the equation that describes the acceleration of the universe; it is acceleration =  ½ Ω_{M} + Ω_{Λ} where Ω_{Λ} is the amount of dark energy and Ω_{M }is (as defined in the book) the ratio of ρ_{m}/ρ_{critical} 2) "found" the equation equivalent to the energy equation in Newtonian cosmology (by integrating the equation of acceleration above); it is curvature = Ω_{M} + Ω_{Λ}  1 the fact that one equation can be derived from the other means that they are equivalent equations, just different ways of looking at the same thing... (in the same sense that F_{net} = ma can be integrated to produce W_{nc} = ΔE, as you may have learned in your Advanced Physics class) 

(always done before class) 
26(4,5): the universe in the recent past, before and since the formation of atoms remember that section 24(4), about finding distances to galaxies needs to be read also 
26(6), the part that we didnt read, that begins on p. 707, with "Dark Energy" 
26(7) and the box above about the two new equations (which do not appear in the book, EXCEPT on the graphs) 
no new reading, but we didn't cover
the old reading (yesterday's), so let's try again early Big Bang.... now postponed to monday 

things you should know the answer to before coming to class 
remind yourself of the plot we drew near the end of class thursday... what are the axes (in words)? make sure you understand the plot and where it came from... is this graph plotted in the text? where? why do both the empty universe and the flat universe have only one possible plot on the graph, whereas the closed and open universes have a variety of graphs on this plot? 
we have extrapolated our newtoniancosmology universes (which exactly match the generalrelativitycosmology universes without dark matter long after the Big Bang) into the future, and in doing so, we have made specific predictions about the flat universe (including age and galaxytrajectory as a function of age), although we have only put bounds on the ages and galaxytrajectories of open/closed universes, and not solved for their ages or galaxytrajectories exactly.... it's time to trace the past history of the universe: how does the temperature (of the universe's cosmic background radiation) vary with the universe's "size"? (and by "size" we really mean "a galaxy's distance from us") how, in turn, does this ("size") relate to the redshift of the light we are just now receiving from galaxies that emitted the light when the universe was "smaller" (and the universe had a temperature that was larger)? (who did a recent presentation on this, and what was the result?) once we have a Tr relationship, how do we get a Tz relationship? (where z = redshift of a galaxy that emitted the light that we are just now receiving) how about a zt (t = age) relationship? how about a ρt relationship (where ρ is the mass density)? (and, in each case, by "relationship" I mean an exact mathematical relationship, e.g., r_{g} α t^{2/3} ) does the text show us any of these relationships, graphically? when i asked (yesterday) if the text showed you an r(t) graph, did it occur to you that we have more than 1 text? apparently not..... 
1) where are the two equations above (with the left hand side in each equation set equal to zero) in figure 2619 on page 711? what COLOR are these lines? (hint: both of these equations are straight lines in figure 2619) do they match the words imprinted above and below the lines on the graph? (beware: a good example of confusing terminology is the graph's use of the word "open" when it actually means "hyperbolic" andof the word "closed" when it actually means "spherical") 2) what are the three sets of observations that astronomers have to decide what kind of universe we live in? what does the evidence point toward? 3) in the past few days that we have spent discussing the 3 types of Newtonian cosmology universes, we have seen that choosing one property of the universe (for example, its density) chooses all the other properties of the universe (including total energy, destiny, geometry, ...) allowing dark energy into the universe opens up new possibilities, as figure 2619 shows.... can you find a universe (i.e., a location in the Ω_{Λ}Ω_{M} plot) that is NOT a Newtoniancosmology universe? (e.g., one that has, say, spherical geometry, but that also expands forever?) 
same stuff as in yesterday's box, < but I would like you to actually do it this time (and i've dumbed down the instructions compared to yesterday's version) and it is particularly crucial that the 2project people do it, because the 1project people supposedly have already (although you wouldnt have been able to tell from yesterday's class) for each of the two equations (the ones in cherry in the class slot for thursday)  1) set the left hand side equal to zero !!! 2) on the diagram on the last page of the Buff book (which should be a Ω_{Λ}Ω_{M} plot) draw the line corresponding to that equation 3) label the lines you just drew appropriately! one is the "acceleration = 0" equation; the other is the "curvature = 0" equation (why " = 0"?) 4) figure out which part of the diagram is a) positive acceleration and which is negative acceleration label! b) positive curvature and which is negative curvature label! (oooh! is one already labeled? correctly?) 5) where are the Newtonian cosmologies on this plot? the new questions from yesterday: 1) why does the plot of energy density (or mass density) of radiation (e.g., the cosmic background radiation) vs age of the unvierse have a steeper slope that the plot of the matter density? (doesn't the density of photons decrease with time at the same rate as the density of matter particles? so why aren't the plots the same?) 2) why doesn't the line for matter have constant slope (on a loglog plot) as we predicted in class yesterday? (what is the slope? is it close to what we predicted?) 3) what observations correspond the brown data in figure 2619? what do astronomers look at? 

homework (written assignments to be turned in) 
homework now for monday, since we didn't progress much yesterday; for 1project people: consider the 5axisgraph on page 42?, buff book.... and let's consider "Size" the independent variable ("Size" r/r_{0 }for any galaxy) for each of the other axes, 1) state the physics law (or combination of laws) that relates this dependentvariable axis back to the independent variable axis & 2) give a numerical example (similar to the one I gave you in class concerning the temperaturesize relation) & 3) do some (or all) of the relationships change over the history of the universe? when do the change? why would that be? 

web stuff 
the discovery of the accelerating
universe and, therefore, of dark energy won the 2011 Nobel Prize in physics... you can find their banquet speeches and Nobel prize lectures at the link above, by clickin on the individual winners 
delayed to at least next tuesday, maybe forever the discovery of the anisotropies in the Cosmic Background radiation won the 2006 Nobel Prize in physics the WMAP people, however, have since done a much better job.... the top 10 things that the Cosmic Background WMAPpers have done... (did you spot the misspelling on their web page?).... they probably think they deserve a Nobel prize too 


two sources of 'cookbook' project ideas for a 2^{nd} project I would expect you to do m faulkes telescope projects on stars or galaxies (some of these are not a substantive project, e.g., making a poster that shows a star's evolution) euhou (although we have already done equivalent labs on cepheids, galaxy mass, & doppler spectroscopy of exoplanets, so please do not choose those) 
if you are doing 2 projects, first project due if you are doing one project, first draft (a very good draft) is due 

of the week 
Decelerating American Science: US shuts down its last particle collider the Habitable Zone for planets around stars narrows: some exoplanets are kicked off the island of potential life Astrobites: each week an astronomy graduate student translate a research article into English for undergraduates why hasn't the whole universe collapsed into an enormous black hole? would your body clock be able to adapt to a 40minutelongerday on Mars? 