Physics 20073 - Study Guide #1

Updated through Thursday, July 10. Current study questions can be found here.

(1)
From the reading "Cargo Cult Science", explain "why the planes don't land" to a typical islander who might ask, in a few sentences. Also, explain why the commercial for Wesson oil is not honest. (TQ)

(2)
From the reading "Cargo Cult Science", briefly summarize the history of the Millikan oil drop experiment. Also, briefly summarize the story of Mr. Young's experiment and why those who ignore his work cannot really trust their conclusions. (TQ)

(3)
Two of the most easily recognizable constellations that are up in the sky at this time of year are the Big Dipper (part of Ursa Major) and Cygnus. Find the following information about these three 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/. To find the approximate altitude and azimuth (azimuth means direction along the horizon, like northeast, south, west, etc), consult the Starry Night software that comes with your book (this is also installed on the computers in the Astronomy lab, which you can use if you finish early in lab) ***OR*** go outside and *FIND* them with your own two eyes on a clear night (all are easily visible this time of year). There are some web sites that will provide you with interactive sky charts, but different computers will work with different sites, so it is up to you to go looking. When you are done, go out at night and find the constellation and explain what you know to a friend or classmate. It's more fun that way. (TQ)

(4)
Visit the "How Stuff Works" website to find out about the Global Positioning System and answer the following: Explain how you could use trilateration to find your location. How many satellites are needed to pinpoint your location on Earth and why? How does a GPS receiver figure out the distance to one of the GPS satellites? (TQ)

(5)
What are sundogs? What causes them? You can find out some information about them at http://antwrp.gsfc.nasa.gov/apod/ap990823.html, an archive of the excellent "Astronomy Picture of the Day" website (a great bookmark to check daily). Try looking for one someday near sunset when there are lots of high, thin icy cirrus clouds near the western horizon. You can often see them as little multi-colored "cloudbows". (TQ)

(6)
Why are planets spherical? (TQ)

(7)
According to the latest news (see http://antwrp.gsfc.nasa.gov/apod/ap060828.html), Pluto is no longer officially a planet! Follow the links on that page and answer: what is the new definition of a planet? (TQ)

(8)
Related to the Pluto debate: What is the Kuiper Belt? What is Sedna, and why do we think it didn't form in its current location, past the outer edge of the Kuiper Belt? A good starting place to answer these questions is the Kuiper Belt information page at the nine planets website: http://seds.lpl.arizona.edu/nineplanets/nineplanets/kboc.html. (Alternate mirror sites for the same Kuiper Belt information are here and here in case the first link doesn't work). Also, David Jewitt has an excellent Kuiper Belt web page: http://www.ifa.hawaii.edu/faculty/jewitt/kb.html. Check out the "Plutinos" page. Jewitt also has a link at the top of the left side with his commentary about whether Pluto should be called a planet. (TQ)

(9)
Explain why we see different constellations overhead at different times during the same night. Does everyone in the northern hemisphere see the same constellations during the night on a given date? Explain your answers (simple diagrams will help).

(10)
Explain why we see different constellations overhead at the same time of night on different days of the year. Again, a simple diagram may help.

(11)
Two possible explanations for the daily motion of the stars in the sky are that either the Earth spins under a motionless sky or that the sky spins over a motionless Earth. Explain why most scientists believed that the Earth was stationary for a long time before the spinning Earth model was finally accepted.

(12)
What are circumpolar stars? Explain why circumpolar stars are found at high celestial latitudes (high declinations). Explain why more circumpolar stars are visible at northern latitudes on the Earth. A diagram may help for each part.

(13)
In your own words, define Right Ascension and Declination and describe how they are used. What is the difference between RA/Dec coordinates and altitude/azimuth coordinates, in general?

(14)
A common misconception is that the seasons are caused by the Earth being closer to or further away from the Sun. Name and explain three different lines of evidence that contradict this idea.

(15)
Although the northern hemisphere of the Earth is slightly closer to the Sun than the southern hemisphere (during the northern hemisphere's summer), this shouldn't result in a significant difference in temperature between the two hemispheres. Explain why.

(16)
What is the ecliptic? What is the difference between the Sun's daily path and its annual path? Be able to draw this difference on a simple celestial sphere diagram.

(17)
Be able to draw a simple horizon diagram (horizon plus hemispherical sky) from Fort Worth's latitude, showing the altitude above the horizon of the NCP, Celestial Equator and June/December paths of the Sun. Be able to use this diagram to explain two reasons why summer months (June) are warmer in Fort Worth compared to winter months (December).

(18)
Be able to draw a simple horizon diagram (horizon plus hemispherical sky) from any latitude on Earth showing the altitude above the horizon of the NCP, Celestial Equator and SCP (if applicable). Also be able to draw the June, Mar/Sep and December paths of the Sun at these various latitudes. Your book's chapter S1 can help with these.

(19)
If the Earth's axis were not tilted (thus, it would make an angle of 90 degrees with respect to the plane of the Ecliptic), would we have seasons in Fort Worth? What would the paths of the Sun look like at different times of the year from Fort Worth? Explain. (TQ)

(20)
For different latitudes on the Earth, explain where the North Celestial Pole can be found on the sky. In other words, use a simple diagram to help explain why the altitude of the NCP above the northern horizon is equal to an observer's northern latitude on the Earth.

(21)
Using a diagram like figure 2.15 in your book (showing the Earth as viewed from one side during Northern summer), be able to show that the day length is longer and sunlight is more direct in the summer.

(22)
Describe two ways that you could refute the misconception that the phases of the Moon are caused by the shadow of the Earth falling on the Moon. Please note that I do NOT want you to describe the actual cause for the phases of the Moon for this question.

(23)
Explain the cause of the phases of the Moon. Given a simple diagram of the Sun and the Earth, be able to identify where the various phases of the Moon would be (e.g. New, Waxing Crescent, 1st Quarter, Waxing Gibbous, Full, Waning Gibbous, 3rd Quarter, Waning Crescent).

(24)
Describe two ways (one mathematical and one observational) that you could refute the misconception that the Moon's angular size when it is near the horizon is much larger than when it is high in the sky.

(25)
What are solar eclipses? Why are some total and some annular? Use the equation of angular size to help answer this question.

(26)
What is a lunar eclipse? Describe what is happening during such an event with the help of a simple diagram.

(27)
Explain why we don't have eclipses every month. What are "eclipse seasons"? A diagram would really help here.

(28)
Another term for the kind of light (electromagnetic radiation) emitted by the sun and most other objects in nature, regardless of their temperature or composition, is "blackbody radiation". Why is it called "blackbody radiation"?

(29)
Know the two basic rules of continuous radiation. Use them to help explain the greenhouse effect on Earth. As part of your answer, address the following point: Greenhouse gases block both incoming and outgoing radiation. Why don't these effects simply cancel each other out, leading to no net change in temperature?

(30)
Explain how we know (by observing the Moon) that the Earth's average temperature is warmed by about 60 degrees Fahrenheit thanks to the greenhouse effect.

(31)
We know that the carbon dioxide abundance in Earth's atmosphere is increasing. How do we know the increase is due to fossil fuel burning and not some natural cyclic process?

(32)
Explain the difference between weather and climate. Why is local temperature variation not really important in terms of global warming?

(33)
Describe how written records can help scientists know the temperature history from hundreds of years ago, even before the invention of the thermometer.

(34)
To go back further, 1000 or more years, scientists look in places like Lake Tuborg or an old forest. Briefly describe what scientists look for when they look at ice layers in a frozen lake and tree rings in a forest. Do thicker layers/tree rings mean warmer (wetter) climate or cooler (drier) climate? Explain why for each case.

(35)
What is the Keeling curve? Why does it go up and down during the Spring and Fall?

(36)
Explain how we can use ice core measurements to estimate the Carbon Dioxide content of the atmosphere hundreds of thousands of years ago. How do current atmospheric conditions compare to those measured during the past 400,000 years?

(37)
According to the fossil fuel industry, increases in Carbon Dioxide will act like "plant food" and accelerate the growth of forests and other plant life. Explain how this hypothesis is being tested and whether the test confirms the hypothesis.

(38)
Will this "greening hypothesis" enable the problem to essentially solve itself by taking all the excess Carbon out of the atmosphere? Explain.

(39)
In computer models, name and explain one example of a positive feedback effect and a negative feedback effect. Why do the computer models have such a wide range of possible predictions about future temperatures?