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




keep up with the latest astro discoveries here




Monday,
February 4,  2013
Tuesday,
February 5,  2013
Wednesday,
February 6,  2013
Thursday,
February 7,  2013
Friday,
February 8,  2013
class


butchered schedule

block D meets:
8:35 - 9:05 am

make sure you have the BUFF book

project-2-people: 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 work-sharing
statement if you are part of a group

reading
(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 log-scale 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?)

2-project people can look below in the homework box to see
what the 1-project 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 1-project people:

consider the 5-axis-graph on page 42?,
buff book....
and let's consider "Size" the independent variable
("Size"  r/r0 for any galaxy)

for each of the other axes,
1) state the physics law (or combination of laws) that relates
this dependent-variable axis back to the independent variable axis
&
2) give a numerical example
(similar to the one I gave you in class
concerning the temperature-size 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

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)





lab





news/discoveries
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
40-minute-longer-day on Mars?








Monday,
January 28
Tuesday,
January 29
Wednesday,
January 30
Thursday,
January 31
Friday,
February 1
class



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 ΩM  +   ΩΛ

where   ΩΛ  is the amount of dark energy

and   ΩM is (as defined in the book) the ratio of  ρmcritical

  2) "found" the equation equivalent to the energy equation in Newtonian cosmology (by integrating the equation of acceleration above); it is

curvature  =      ΩM  +   ΩΛ    -   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 Fnet = ma can be integrated
to produce Wnc =  ΔE, as you may have learned
in your Advanced Physics class)


reading
(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 newtonian-cosmology universes
(which exactly match the general-relativity-cosmology 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 galaxy-trajectory as a function of age),
although we have only put bounds on
the ages and galaxy-trajectories of open/closed universes,
and not solved for their ages or galaxy-trajectories 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 T-r relationship,
how do we get a T-z relationship?
(where z = redshift of a galaxy that emitted the light
that we are just now receiving)

how about a z-t (t = age) relationship?

how about a ρ-t relationship (where ρ is the mass density)?

(and, in each case, by "relationship" I mean an exact
mathematical relationship,
e.g.,  rg α  t2/3  )

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  26-19 on page 711?
what COLOR are these lines?

(hint:  both of these equations are straight lines in
figure 26-19)

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 26-19 shows....

can you find a universe (i.e., a location in the ΩΛ-ΩM plot)
that is NOT a Newtonian-cosmology 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 2-project people do it, because the 1-project 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 ΩΛ-ΩM 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 log-log 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 26-19?
what do astronomers look at?


homework
(written assignments
to be turned in)






homework now for monday, since we
didn't progress much yesterday;
for 1-project people:

consider the 5-axis-graph on page 42?,
buff book....
and let's consider "Size" the independent variable
("Size"  r/r0 for any galaxy)

for each of the other axes,
1) state the physics law (or combination of laws) that relates
this dependent-variable axis back to the independent variable axis
&
2) give a numerical example (similar to the one I gave you in class concerning the temperature-size 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

lab


two sources of 'cookbook' project ideas for a 2nd 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)

eu-hou
(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



news/discoveries
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
40-minute-longer-day on Mars?



january pages
december pages
november pages
october pages
  september pages
  august pages