Due Wednesday Oct 18 by 10 pm

Submit your assignment through Canvas via the HW2 link.

Most of these questions will require doing research/reading outside of the course material. That's one of the essential points of homework.

In addition, you may work with up to two other class members to form a group of 3 for doing homework assignments.

1. Explain the difference in cultural conditions in the time of Nicholas of Cusa compared to Bruno which lead to the latter being burned at the stake even though he mostly just re-iterated what Cusa had said.
   
   
   
2. Open the simulation and select Galaxies
   
   Your screen should look like this:
   
   
   
   For this exercise you are only to measure these galaxies:
   
   NGC 2903, NGC 3147, NG 3368, NGC 3627, NGC 5548, NGC 6181, NGC 6764, NGC 7469
   
   For each galaxy you will measure a diameter and a radial velocity (from redshifted spectral lines).
   
   You will then enter those data pairs, X = diameter, Y = velocity, using this plot application
   
   
   • Make sure you select Scatter and not Connected. Enter the data as an X,Y pair and get Plot/Update to see the data.
     
     
   • When your plot is fininshed (i.e. has 8 points on it) then make a screen shot of it and integrate that into your homework document.
     
     
     The screen shot below shows what this application looks like with fake data points on it
     
     
     
     
   
   
   In the simulation your will measure a diameter and a redshift (velocity). Refer to this tutorial on how to estimate a velocity based on spectral line shifts to longer wavelengths due to motion away from the observer.
   
   For an example, I will go through how to measure the diameter and redshift for one galaxy not on the list. NGCC 6643
   
   After I click on NGC 6643 this screen appears:
   
   
   
   which is the REAL spectrum of this REAL Galaxy. Now this galaxy has both emission lines (upward features) and absorption lines, downward features. Its usually easiest to deal with emission lines. The tutorial that you went through tells you that Hβ has an emission line at 4861 Angstroms. For NGC 6643 this line will be measured at a wavelength of 4885 angstroms, or about 25 angstrom shift to the red.
   
   The redshift is then (25/4861) = .005
   
   Multiply that by the speed of light, 300,000 km/s to get a velocity of 0.005 * 300,000 = 1545 km/s (ignore what I say in the video - this is the right velocity).
   
   Now refer to this YouTube Video Tutorial:
   
   
   
   Now that you have done the exercise for all 8 galaxies you are to turn in two things.
   
   
   A. A screen shot of your plot of diameter versus velocity
   
   B. What assumption does Hubble have to make in order to turn this into a velocity-distance relation, from which it can be seen that more distant galaxies are moving at higher radial velocities, than more nearby galaxies.
   
   
   
   
   
3. Summarize the Shapley-Curtis debate and its implications on the overall size of our Galaxy and the size of the Universe. What kinds of evidence did Shapely use to promote his basic premise that our Galaxy was in fact, the entire Universe?
   
   
   
4. Google (and don't be lazy and rely on the usually erroneous and incomplete Wikipedia) on "Andrew Mckellar Microwave Background". McKellar actually detected the MWB in 1941 (!) but did not realize it at that time. Speculate why you think he was unable to put his data together to claim initial discovery and hence a future Nobel prize.