Physics 20073 - Fall 2009 Study Guide #2 (MWF daytime class)

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Updated through Wednesday, October 21.

(50)
Two of the most easily recognizable constellations that are up in the sky at this time of year are Pegasus and Sagittarius. Find the following information about these two constellations:

This is pretty easy to find on the web. A good place to go for mythology is http://www.emufarm.org/~cmbell/myth/myth.html, but remember to keep your summary fairly short so it is easy to remember the most important parts. A good place to go for simple star charts is http://www.dibonsmith.com/constel.htm. For star names and other information, try http://www.astro.wisc.edu/~dolan/constellations/. (TQ)

The following four thought questions are based on the January 2008 Scientific American article, "A Solar Grand Plan", available as a pdf from the TCU library's online archives. To access this article electronically, follow these instructions:

(1) Go to www.lib.tcu.edu.
(2) On the drop-down menu next to the search box, change it from "Words Anywhere" to "Journal/Serial name begins with..."
(3) Type "Scientific American" into the search box, then click on the Search button.
(4) On the search results page, click on "*SCIENTIFIC AMERICAN*"
(5) On the next page, in detail record #1, click on the fourth "full text available..." link. It reads "Full text available to the TCU community from Scientific American Archive Online: 01/01/1993 to present".
(6) You may have to type in your TCU ID number at this point if you are accessing the library from off-campus.
(7) Type the title of the article or your subject of interest in the search box. For example, "nuclear power" or "global warming" or "solar grand plan". You can then view the text or download a pdf file containing the entire article with diagrams and pictures.

(51)
One drawback to solar energy is that the Sun doesn't always shine on your energy collectors, so to make it reliable, you need to store power for use when the Sun isn't shining. Describe how the authors propose using underground caverns as a way of storing energy. (TQ)

(52)
Describe how salt can be used as another way of storing power without resorting to traditional batteries. (TQ)

(53)
Explain briefly why a transition to a solar energy infrastructure would result in lower US energy consumption by 2050. (TQ)

(54)
Explain two arguments the authors use to justify the $420 billion price tag that this project would accrue over 30 years. (TQ)

(55)
Explain how nuclear fission generates energy (where, exactly, does the energy come from in the reaction).

(56)
What prevents most countries from having nuclear reactors or weapons? What is "enriched" Uranium? What is "depleted" Uranium, and what is one of its main uses?

(57)
Explain why nuclear fusion reactions require extremely high temperatures.

(58)
Where does the energy come from in fusion reactions? What are Deuterium and Tritium? Explain how nuclear fusion (D-T fusion) generates dangerous waste products.

(59)
Why is it difficult to contain fusion reactions? Explain inertial and magnetic confinement.

(60)
What is a Q-value, and how does it relate to the viability of nuclear fusion as an energy source?

(61)
Why is the sky blue during the daytime? Why does the sun appear red at sunset? Why does the moon appear red during total lunar eclipses?

(62)
Photos from the surface of the Moon (you can find several in your book) demonstrate that even during the daytime, when the Sun is shining on the surface of the Moon, the sky is pitch black. Explain why.

(63)
Explain how spectral absorption and emission lines are created (including Kirchoff's laws, from book's diagram in chapter 5). Given a simple energy level diagram for an atom, be able to state what energies of light can be emitted or absorbed (without taking into account the electron possibly leaving the atom altogether or coming in from the outside).

(64)
Explain why each different element has its own unique spectral fingerprint (what is a spectral fingerprint and how is it created?). How do we use this knowledge to determine the composition of other planetary atmospheres?

(65)
State the three rules associated with Doppler shifting.

(66)
Explain the difference between radial and transverse velocity, with the help of a simple diagram.

(67)
Explain how we use the Doppler shift to determine the rotation speed of planets. How and why does the rotation speed of a planet affect the spectral lines coming from that planet?

(68)
Briefly explain the capture hypothesis for the origin of the solar system. Name and briefly explain three arguments that tend to contradict this hypothesis.

(69)
Briefly explain the catastrophe hypothesis for the origin of the solar system. Name and briefly explain two arguments that tend to contradict this hypothesis.

(70)
Read http://www.nineplanets.org/hypo.html#nemesis to find out about the Sun's hypothetical companion star, Nemesis. Based on all-sky searches for nearby and extremely dim stars, it seems unlikely today that such a star exists. Why did some Astronomers believe that such a star exists? How would such a star affect the Earth? (TQ)

(71)
A common belief among Astronomers is that the initial collapse of our solar nebula was triggered by some event like a nearby supernova. Recent evidence from the Chandra X-Ray observatory, however, has cast doubt on that hypothesis. Read http://chandra.harvard.edu/press/01_releases/press_090601solar.html and answer the following: What evidence (having to do with isotopes) makes some Astronomers believe that a supernova was involved in the origin of our solar system? How do the Chandra observations explain the isotope evidence discussed above without resorting to a supernova? (TQ)

The following five thought questions are from the article "What Is a Planet?" from the January 2007 issue of Scientific American. You can find it online using the instructions given previously in study guide #2. I suggest doing a search for "pluto", and it will be the 1st item found in that search once you are on the last step of the process. If you try to search for "What Is a Planet?", it won't work.

(72)
According to the International Astronomical Union (IAU), what is the official definition of a planet now and why does this definition exclude Pluto from having the status of a planet? (TQ)

(73)
It was once thought our solar system had over 20 planets before the definition of planet was last modified in 1852. Explain what all of these extra planets were and why they were demoted from planet status. (TQ)

(74)
What triggered the change in definition of planets that now excludes Pluto? (TQ)

(75)
The authors propose an improvement of the definition of planets based on a factor represented by the greek letter mu. What is "mu"? (TQ)

(76)
Some astronomers argue that planets should be defined only by their intrinsic properties (such as size, shape or composition) rather than by their location or surroundings. What is the authors' counterargument to this idea? (TQ)

(77)
Explain why the solar nebula collapsed into a disk shape as a result of its rotation.

(78)
Given the condensation temperatures for the four main components of planets (metal, rock, ice and gas) and an indication of the temperature in various parts of the solar nebula disk, be able to identify and explain which components you would expect to condense into solid form at various locations in the solar system.

(79)
Explain how evidence found in meteorites tends to confirm our ideas about the accumulation phase of the origin of the solar system.

(80)
Name and briefly explain three reasons why Jupiter is so much larger than the Earth. As part of your answer, be sure to explain both ways in which ice particles make it easier for larger planets to form.

(81)
Explain why lower mass gas particles in a gas tend to move more quickly than high mass gas particles.

(82)
Name and explain two reasons why the Earth cannot accumulate Hydrogen gas while Jupiter can. One has to do with temperature, the other with escape velocity.

(83)
Why does the Earth have a hard time capturing Hydrogen while easily maintaining an abundance of gases like Carbon Dioxide?

(84)
NASA's web pages for the Terrestrial Planet Finder contain details about various techniques for finding extrasolar planets. Visit http://planetquest.jpl.nasa.gov/science/finding_planets.cfm and briefly explain two other indirect techniques for finding extrasolar planets besides the "Doppler wobble" technique and the "transit" technique, both of which we will discuss in class. (TQ)

(85)
From http://planetquest.jpl.nasa.gov/science/finding_life.cfm, answer the following: What is the habitable zone? Which gas, oxygen or ozone, is probably a better indicator of the existence of life on a planet and why? (TQ)

(86)
Read the press release at http://astron.berkeley.edu/~gmarcy/hd/press_release.html and answer the following: What is significant about star HD 209458? What is different about the HD 209458 system compared to other systems in which Marcy and Butler have used Doppler wobbling observations to suggest the existence of planetary companions? How does the planetary companion of HD 209458 compare to Jupiter, and how do we estimate its size and therefore its density? (TQ)

(87)
Read the comments by Phil and Phyllis Morrison at http://astron.berkeley.edu/~gmarcy/morrisons_transit.html and answer the following: The Kepler probe has a mission that is described by the authors and a purpose to find extrasolar planets. How will the Kepler probe find (perhaps lots of) planets without using Doppler wobble measurements? (TQ)

(88)
What are the three ingredients necessary for life? What is a possible source for each ingredient?

(89)
On the 5-km highway of time representing the history of Earth, what length accurately reflects all of recorded human history?

(90)
Critics of evolution wonder how a process based on random chance could result in extremely complex organisms. How do biologists respond to this argument?

(91)
What discovery did the Magellan spacecraft make about the recent geological history of Venus?

(92)
What recent evidence discovered in Antarctica implies that life may have once existed on Mars?

(93)
What is the habitable zone? Explain how recent discoveries of life in extreme environments (e.g. black smokers, worms in methane ice, etc.) has affeted our view of a habitable zone. What is a "gravitational" habitable zone?

(94)
Explain how we use Doppler shifting evidence to deduce the existence of planets around other stars. How do we estimate the mass of the companion? How do we estimate the distance from the companion planet to its parent star?

(95)
Explain why we cannot necessarily believe that indirect observations of planetary companions via Doppler wobbling are truly planetary companions. Are our assumed companion planet masses higher or lower than true planet masses in tilted systems? Explain.

(96)
Explain the details and significance of the discovery of an eclipsing (or transiting) extrasolar planetary system. How did Astronomers know just by looking at the light curve that this was an eclipsing system (how is this dip different from other variations in a star's brightness)? Why was this discovery important for extrasolar planet hunters?

(97)
Explain why searches for other planetary systems so far have been biased in favor of discovering high mass planetary companions as well as planetary companions that are very close to their parent stars.

(98)
Explain the two major (gravity-related) heat sources that made the early, forming Earth so hot that it was completely molten throughout. Describe the current heat source that keeps Earth's interior partially molten.

(99)
What is a half-life? Be able to work your way through an example of a radioactive parent isotope sample as it decays into stable daughter atoms. For example, "The half-life of a parent is 4000 years. The original composition is 280 parents and 50 daughters. The current composition is 35 parent atoms. How old is the rock, and how many daughter atoms are present?"

The following four Thought Questions come from the Scientific American article "Snowball Earth" from the January 2000 issue.

(100)
Describe the evidence that led scientists to believe the continents were all clustered around equatorial latitudes during the geological era 600 million years ago. (TQ)

(101)
What is albedo? Describe the positive feedback cycle that leads to "Snowball Earth" once ice begins to cover the continents at mid-latitudes. (TQ)

(102)
What is the hypothesis presented in the article that can explain how life survived on a planet Earth where the average temperature was perhaps 50 degrees Celsius below zero? (TQ)

(103)
How was this runaway freeze reversed, according to the theory presented in the article? Describe the feedback cycle that warmed the Earth out of the deep freeze. (TQ)

(104)
Describe how stable isotope siblings of parents and daughters are used to determine the original composition in a rock. For example, "When a rock solidifies, the number of parent atoms is one-half the number of stable sibling atoms. The parent has a half-life of 10,000 years. The current composition is 20 parents, 640 daughters and 640 stable siblings. How old is the rock, and what was the rock's original composition?"

If you are interested in a more detailed version of the "age of the Earth" debate, I recommend http://www.talkorigins.org/faqs/faq-age-of-earth.html as a good source (though perhaps too technical in places) with lots of helpful references. This is not a required reading.

(105)
Name and briefly explain the two things necessary in a planetary interior for the planet to have a magnetic field.

(106)
Explain how the Earth's magnetic field interacts with the solar wind to both protect life on Earth and create the aurorae visible in the atmosphere near the North and South polar regions.

(107)
Explain why the Earth has two tidal bulges as a result of the Moon's gravity.

(108)
What is the difference between spring tides and neap tides? Which type of tides should we expect to see during new moon? Full moon? 1st quarter? Explain.

(109)
What causes the Earth's tidal bulges to "lead" the Moon in its orbit? Describe this and be able to draw a simple diagram explaining this effect. How and why does this affect the rotation speed of the Earth over time?

(110)
Explain how the Earth's rotation, combined with the tidal bulges from the Moon, result in the Moon's orbital distance from the Earth slowly increasing over time.

(111)
Explain the phenomenon of tidal locking, which is why the same face of the Moon always points at the Earth.