Physics 20073 - Study Guide #3

Updated through Thursday, July 24. Current study questions can be found here.

(90)
What are the three ingredients necessary for life? What is a possible source for each ingredient?

(91)
On the 5-km highway of time representing the history of Earth, what length accurately reflects all of recorded human history?

(92)
Critics of evolution wonder how a process based on random chance could result in extremely complex organisms. How do biologists respond to this argument?

(93)
What discovery did the Magellan spacecraft make about the recent geological history of Venus?

(94)
What recent evidence discovered in Antarctica implies that life may have once existed on Mars?

(95)
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?

(96)
Two of the most easily recognizable constellations that are up in the sky at this time of year are Cassiopeia and Ursa Minor. Find the following information about these 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 Thought Questions come from the Scientific American article "Snowball Earth" from the January 2000 issue. The questions are asked in the same order they are answered in detail in the article. See previous study guide for detailed instructions on how to access these articles in pdf format online.

(97)
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)

(98)
What is albedo? Describe the positive feedback cycle that leads to "Snowball Earth" once ice begins to cover the continents at mid-latitudes. (TQ)

(99)
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)

(100)
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. (this is also described briefly at the end of the next article I've assigned to you) (TQ)

The following four Thought Questions come from the Scientific American article "The Origins of Water on Earth" (September 2003).

(101)
How do we know that water has been present on the Earth since shortly after its formation? (TQ)

(102)
Briefly explain two possible ways early Earth's water could've been "lost" and not become a permanent part of Earth's oceans. (TQ)

(103)
Explain the evidence from recently-observed comets (such as Halley) that implies most of Earth's water probably did not come from comets. (TQ)

(104)
What is the Faint Sun paradox and how has it been "resolved" by our atmosphere? (TQ)

(105)
Read the EPA's web pages about ozone at http://www.epa.gov/ozone/science/index.html to answer the following question: Briefly explain two reasons (one having to do with wind patterns and one having to do with ice clouds) why the ozone depletion largely occurs over the Antarctic each year rather than uniformly in the rest of the Earth's atmosphere (it may take some searching through the web site, but the answer is very clearly there). (TQ)

(106)
Although the Moon has no atmosphere, recent missions surveying the lunar surface have revealed the presence of water-ice on the Moon's surface. Read http://nssdc.gsfc.nasa.gov/planetary/ice/ice_moon.html, a web site with detailed results of the Lunar Prospector and Clementine missions, and explain how it is possible that water-ice has survived on the Moon for all these billions of years without sublimating away and escaping. Where did the ice probably come from? (TQ)

The following five Thought Questions can be answered by reading the Scientific American article "Mercury: The Forgotten Planet" from the 2003 special edition on the solar system.

(107)
Explain the reasoning that leads us to believe that a large fraction of Mercury's mass consists of iron. (TQ)

(108)
Explain why we think substantial quantities of sulfur may be present in the interior of Mercury (this has to do with its magnetic field). (TQ)

(109)
What is the Mercurian Grid, and how do we think it formed? (TQ)

(110)
Why are craters on Mercury typically larger than craters found on the Earth's Moon? (TQ)

(111)
Explain two sources of the gases in Mercury's tenuous atmosphere. (TQ)

(112)
What is differentiation? How does it help explain the current organization of the Earth's interior (metal core, rocky mantle)? How do we know the Earth was once very hot compared to today?

(113)
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

(114)
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?"

(115)
Briefly explain the concept of sources and sinks in the Carbon cycle. Give at least two examples of sources and two examples of sinks.

(116)
Argon gas is called a "tracer" because it is one of the few gases in our atmosphere that maintains its original abundance from the original (primitive) atmosphere to the modern (secondary) atmosphere. What two properties of Argon gas make this possible? Explain why each one is important.

(117)
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.

(118)
What is the ozone layer, and why is it important for life on Earth? Explain how the production of Chloroflourocarbons (CFC's) results in the partial destruction of Earth's ozone layer.

(118)
Name and briefly explain the two things necessary in a planetary interior for the planet to have a magnetic field. 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.

(120)
Explain why the Earth has two tidal bulges as a result of the Moon's gravity.

(121)
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?

(122)
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.

(123)
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.

(124)
Explain the phenomenon of tidal locking, which is why the same face of the Moon always points at the Earth.

(125)
Explain how the maria on the Moon formed and why their appearance differs from that of the lunar highlands.

(126)
Explain how the crater density and relative ages of the maria and highlands reveal the existence of the era of early bombardment. Talk about crater retention age and the assumption involved and what makes us think the assumption is wrong.

(127)
Explain why the Moon lacks a magnetic field. Explain why it lacks an atmosphere.

(128)
Explain why the surface of the moon maintains a record of the era of early bombardment (the first half-billion years after the formation of the planets) while Earth's surface does not.

(129)
Explain the capture theory of the Moon's formation in a sentence or two. Explain why this theory has problems explaining the mass ratio of the Moon compared to the Earth and the isotope fingerprints of the Earth and the Moon.

(130)
Explain the Co-Creation theory of the Moon's formation in a sentence or two. Explain why this theory has problems explaining the rock/metal ratio in the Moon and the lack of volatiles in the Moon compared to the Earth.

(131)
What are volatiles? The Moon has a lower abundance of volatiles than the Earth's mantle. What does this fact imply about the history of the material that formed the Moon, compared to the history of the material that formed the Earth's mantle?

(132)
Explain the Fission theory of the Moon's formation in a sentence or two. Explain why this theory successfully predicts the rock/metal ratio in the Moon and the isotope fingerprint similarity between Earth and Moon.

(133)
Why does the Fission theory have trouble explaining the difference in abundance of volatiles in the Earth and Moon? Also, explain how the current (relatively slow) rotation of the Earth is a problem for the Fission hypothesis.

(134)
Explain the Giant Impact theory of the Moon's formation in a sentence or two. Explain why this theory successfully predicts the rock/metal ratio in the Moon, the isotope fingerprint similarity between Earth and Moon, and the relative lack of volatiles on the Moon compared to the Earth.

(135)
Some scientists are wary of the Giant Impact theory because it does not really qualify as a falsifiable theory. Explain why. Explain what falsifiable means and why a scientific theory should be falsifiable (you may wish to revisit relevant sections of the Philosophy and the Scientific Method reading from the Physics 20073 home page).

(136)
Explain why some scientists did not anticipate Mercury would have a significant magnetic field. The fact that a weak magnetic field does exist on Mercury implies that the interior is partially molten. Describe the heat source we think is present on Mercury and how it works to keep the interior partially molten.

(137)
One of the three theories to try to explain Mercury's big metal core is the condensation theory. Briefly describe this theory and describe what observation would confirm it.

(138)
Briefly describe the evaporation theory that attempts to explain Mercury's core and describe an observation that would confirm it.

(139)
Briefly describe the giant impact theory that attempts to explain Mercury's core and describe an observation that would confirm it.