Study the following video and answer the questions below it. Or else.
1. Use the information provided about the Earth’s orbital speed to estimate the mass of the Sun. (Assume a circular orbit; 1 AU is 1.5 × 1011 m.)
2. Use the information provided about the Sun’s motion around the Galactic Centre to estimate the total mass interior to the Sun’s orbit. (Assume a circular orbit and that the mass distribution is spherically symmetric; you may quote Newton’s shell theorem without proof.)
3. Use the answer to Q2, and other information provided in the video, to estimate the mean matter density in the Milky Way.
4. Use the information provided about the size, shape and stellar content of the Milky Way to estimate the mean number-density of stars interior to the Sun’s orbit.
5. Use the answers to Q3 & Q4 to estimate the mean mass-to-light ratio of the Galaxy.
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How good is a spherically-symmetric approximation for a galaxy? The gravity from a disc should be higher than that from a shell because to turn a shell into a disc you move the matter down into the plane, slightly closer to the orbiting object.
Phillip: I’m not convinced that the Python sketch is a Bergman parody – the figure of Death was quite common in a certain category of play. Bergman’s innovation was the chess game vs Death in 7th Seal, and it was rather asking for the treatment it got in De Duva.
Which is the great ad lib line – there’s a lot of muttering around 6:20+?
For me, The Best Intentions is Bergman’s finest script, about his parents’ complex courtship and unhappy marriage to the point where his mother is pregnant with him. It was directed by someone else, perhaps because Bergman was aging, and I believe it is even better than Fanny and Alexander, to which it is a prequel and which Bergman directed himself.
In the Dark 
June 13, 2010 at 12:30 pm
[…] This post was mentioned on Twitter by chrislintott, Hannah H. Hannah H said: RT @chrislintott: Answers on a postcard please. http://tinyurl.com/3xzk75f (you may leave before the end of the examination) […]
June 14, 2010 at 10:00 am
How good is a spherically-symmetric approximation for a galaxy? The gravity from a disc should be higher than that from a shell because to turn a shell into a disc you move the matter down into the plane, slightly closer to the orbiting object.
June 14, 2010 at 11:38 pm
It’s not very good for the disk component, but probably not bad for the central “bulge” or the extended halo within which it resides.
June 15, 2010 at 9:48 pm
Phillip: I missed any parody of 7th Seal in Meaning of Life. Where was it, please?
I’m glad to have the definitive Bergman parody De Duva on DVD, taken from TV. In it, they play death not at chess but at badminton.
Anton
June 16, 2010 at 8:37 pm
Phillip: I’m not convinced that the Python sketch is a Bergman parody – the figure of Death was quite common in a certain category of play. Bergman’s innovation was the chess game vs Death in 7th Seal, and it was rather asking for the treatment it got in De Duva.
Which is the great ad lib line – there’s a lot of muttering around 6:20+?
For me, The Best Intentions is Bergman’s finest script, about his parents’ complex courtship and unhappy marriage to the point where his mother is pregnant with him. It was directed by someone else, perhaps because Bergman was aging, and I believe it is even better than Fanny and Alexander, to which it is a prequel and which Bergman directed himself.
Anton
June 17, 2010 at 9:22 pm
That ad lib line is fast, but doesn’t help. I was confused when it wasn’t followed up.