These readings are to be completed before class on the indicated dates. These are also the dates when you should prepare reading notes and turn them in at the end of class. Note that there are no reading assignments for the dates devoted to in-class exercises (and review).
Wednesday, August 24: Motions of the stars through our sky
Your assignment is to learn how the stars appear to move through our sky during the night. The goal here is for you to be able to visualize this motion and describe it accurately in your own words. You should also be able to sketch the motion. Additional questions: How can you use the stars to tell time? How does the apparent motion of the stars change as you move to different places on earth? How can you use the stars to determine the earth's size? How did the Ancient Greeks explain this apparent motion?
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Monday, August 29: The Sun and the Seasons
Your assignment is to learn how the sun appears to move through our sky, and how the sun's position in the sky relates to earth's temperature. Why is it warmer in the tropics than near the poles? How does the sun's apparent motion vary over the course of the year, and how does this relate to our seasons? How does the sun's apparent motion vary with latitude?
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Wednesday, August 31: The Moon and Eclipses
Your assignment is to learn about the motion of the moon through our sky and the phases of the moon. How can you tell that the moon shines by reflecting sunlight? Given the position of the moon and the sun in our sky, how can you predict the moon's phase? How can you tell that the moon is closer than the sun? What happens when the sun, moon, and earth are lined up directly?
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Wednesday, September 7: Motions of the Planets
Your assignment is to learn about naked-eye observations of the planets Mercury, Venus, Mars, Jupiter, and Saturn. What do they look like from earth? How do they move through the sky? What clues from planetary motion did Copernicus use to infer that the earth is also a planet, orbiting the sun?
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Friday, September 9: Kepler's laws
Please continue to study the details of the planets' orbits. How can we determine the relative sizes of the orbits? What are the shapes of the orbits? How does the speed of a planet change as it moves around its orbit? Which planets move faster, and which move slower?
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Wednesday, September 14: Galileo and Newton
Your main assignment for today is to learn about Galileo's discoveries with the first astronomical telescope. What does it take to make a simple telescope? What, exactly, was Galileo able to see? (These days you can see the same things in a typical pair of binoculars.) Why were his discoveries historically important?
In addition, please start reading about Isaac Newton and his laws of motion--especially the law of inertia (Newton's first law).
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Friday, September 16: Newton and Gravity
Please continue learning about Newton's laws of motion, concentrating on the concept of a "force" and how forces change the motion of an object. Also study Newton's law of gravity. Why (according to Newton) do a dropped apple and a dropped pumpkin fall at almost exactly the same rate? You should be able to explain how Newton's laws of motion and gravity account for the orbital motions of planets and moons. You should also understand how gravity becomes weaker (but never disappears) when objects are farther apart.
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Wednesday, September 21: The Terrestrial Planets
We turn now to a detailed study of our solar system, as revealed by spacecraft that have visited the planets and their moons, sending back data and pictures. For today, please study the four "terrestrial planets" (Mercury, Venus, Earth, and Mars), as well as earth's moon. You should be able to describe the similarities and differences among these five worlds, in terms of the following:
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Friday, September 23: The Jovian Planets
Continuing your tour of the solar system, please study the four "Jovian planets" (Jupiter, Saturn, Uranus, Neptune) and their many moons. How do these planets differ from the terrestrial planets? What are they made of? How do they compare in terms of size, distance from the sun, temperature, etc.? Which of their moons seem most interesting?
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Monday, September 26: Solar System Debris
Continuing your tour of the solar system, please read about all the "little stuff" that's orbiting around the sun: asteroids, comets, Kuiper belt objects (including Pluto), etc. Where are these objects generally found? How do their orbits differ from the orbits of the eight major planets? How often do they collide into other objects, and what happens then?
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Wednesday, September 28: Space Exploration
Having toured the solar system, let's pause to consider the spacecraft that have given us all these amazing images and other data about the planets, their moons, and smaller objects. How do spacecraft get to such distant places? How long does it take them to get there? What were some of the historic milestones in space exploration? How much does all this cost, and who pays for it? What are the roles of human space flight vs. robotic spacecraft? If you were in charge of NASA's budget for next year, how much money would you provide, and how would you allocate it among various projects?
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Monday, October 3: Formation of the Solar System
Please read about the origin of the solar system, according to the most recent theories and calculations. How do we determine the age of the solar system? What observable patterns in the solar system are explained by knowing the solar system's early history? What clues about our solar system can we discover by looking at other solar systems, and at places where new stars are forming?
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Wednesday, October 5: Light and Energy
As we look out beyond our solar system, our knowledge is limited to what we can learn from the light and other natural signals that happen to come our way. It's about time, therefore, that we pause to learn more about the physical properties of light. What is light, anyway? How fast does it travel? What do we mean when we say that light carries energy?
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Monday, October 10: More about Light
Looking at the properties of light in more detail, your main assignment for today is to understand what we mean by a spectrum (plural spectra), and to become familiar with the different types of spectra given off by different light sources: Continuous (thermal) spectra, emission spectra, and absorption spectra. How does the temperature of a source affect its spectrum? How does the motion of a source affect its spectral lines? How do you split light apart into a spectrum in the first place?
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Wednesday, October 12: Telescopes
Now that you know all about light, please turn your attention to the instruments that we use to gather and record light. What does a telescope do, and how do telescopes work? What are some of the different types of telescopes? What determines the light gathering power of a telescope? What kinds of light detectors are used with telescopes? What are the advantages of putting a telescope in space?
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Monday, October 17: Measuring the Stars
We now begin a major topic of this course: studying the properties of the stars. Because they're so far away (except for our sun), this isn't easy. Please read about how we determine the following properties of stars: distance, motion, brightness, and temperature. (By the time you come to class, you should be able to explain these methods to a classmate!)
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Wednesday, October 19: Classifying the Stars
Continuing your study of stellar properties, it's now time to start looking for patterns. How do stars vary in their distance from us, luminosity, and temperature? Do hotter stars tend to be brighter? What are the exceptions to the general trends?
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Wednesday, October 26: What Makes the Stars Shine?
Your assignment is to figure out what makes the stars shine. You'll need to read about nuclear fusion reactions, and be able to visualize these reactions with "cartoons" of protons and neutrons and gamma rays and such. Why do nuclear fusion reactions occur only at very high temperatures? How does the rate of nuclear fusion depend on the mass of the star?
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Friday, October 28: Red Giants and White Dwarfs
What happens when the core of a star runs out of hydrogen fuel? Please read about how old stars turn into red giants and then (usually) into white dwarfs. You should be able to explain what's happening inside either of these types of old stars. But if you can't explain exactly why old stars expand into giants, don't worry; I don't quite understand this myself, and I've never taken the time to go through all the math.
Be sure to look at plenty of pretty pictures of so-called planetary nebulae! (While you're at it, look at pictures of the much larger nebulae that stars form out of in the first place.)
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Monday, October 31: Supernovae and Neutron Stars
There are two approaches to today's topic: observational and theoretical. Please read about both.
Observational approach: What does a nova or a supernova look like (from earth)? What does a supernova remnant look like? What other signal, besides light, can be detected from a supernova? How do we detect pulsars?
Theoretical approach: What is the underlying explanation of a nova, or a supernova? What's the difference between a type-1 and type-2 supernova? How have past supernova explosions affected our solar system? What is a neutron star, and why to they tend to spin so fast while beaming out radio waves?
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Wednesday, November 2: Black Holes
Don't expect to understand the theories of relativity in one day! But please try to get a grasp of what relativity is all about, the difference between "special relativity" (a revision to our understanding of space and time) and "general relativity" (another such revision, taking gravity into account). Why can no signal travel faster than the speed of light? What is gravity, according to general relativity theory? What, exactly, is a black hole? How can we detect black holes if they can't give off any light?
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Monday, November 7: The Milky Way Galaxy
It's now time to take another step back and look at how the stars (and other objects) around us are organized. What is the size and shape of the system of stars to which we belong? What does it look like from inside, and what would it look like from outside? What are its major components, besides individual stars? Why can't we see the center of the Milky Way (or can we)? How do we measure the size of the Milky Way?
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Wednesday, November 9: Galaxies
Now zoom out further and look at all the other comparable star systems like our own: the galaxies. How are they similar, and how are they different? What are a few of the most familiar examples? How far away are they? How are they arranged in space? How do we even measure such tremendous distances?
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Monday, November 14: The Expanding Universe
Please read about Edwin Hubble's remarkable discovery: The galaxies are moving apart from each other! What exactly is the pattern (trend) that Hubble discovered? What does it mean? How do you measure the distance and velocity of something so far away? What do we mean by the "age of the universe", how do we calculate it, and what are the sources of uncertainty in the calculation?
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Wednesday, November 16: Quasars
Read about quasars and active galactic nuclei. Why was the discovery of quasars so surprising, and what do they tell us about the history of the universe? What exactly are they, anyway?
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Monday, November 21: The Cosmic Background Radiation
When we look beyond (or before) the most distant galaxies, 13.7 billion years into lookback time, what do we see? Answer: The cosmic background radiation. What is it? How do we detect it? What does it tell us about the early universe?
As you read about the background radiation, you will surely see false-color images that map the intensity of the radiation over the whole sky. Pay attention to these images and try to understand exactly what the colors mean.
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Wednesday, November 23: The Early Universe
The cosmic background radation tells us that the universe was once filled with hot plasma, which cooled as the universe expanded. The farther back in time we extrapolate, the hotter and denser the plasma was. How can we visualize this plasma? What happened when the plasma was hot enough to trigger nuclear reactions? What relics are still left over from this very early stage in the history of the universe?
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Monday, November 28: Dark Matter and Dark Energy
We now turn to the most pressing unanswered questions in cosmology: What is the dark matter that gives galaxies most of their mass, and what is the dark energy that is causing the expansion of the universe to accelerate? How do we even know that dark matter and dark energy exist? How can we visualize these things? What could they be?
This would also be a good time to consider any other lingering questions you have about cosmology. Write them down and ask in class!
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Wednesday, November 30: The Anthropic Multiverse
In recent years, as cosmologists have confronted the deepest questions about the nature and origin of the universe, some have embraced the highly controversial ideas of a "multiverse" and the so-called "anthropic principle." Learn about these ideas, and see what you think!
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Friday, December 2: Life in the Universe
A good way to review the whole course is to step back and ask whether there could be life elsewhere in the universe. What do we know about the chance of there being life elsewhere in our solar system? What about other solar systems? Given the huge number of galaxies in the observable universe, is there an overwhelming chance that life exists elsewhere--or is life so rare that earth is the only lucky planet? How can we go about looking for life elsewhere? Even if it's out there somewhere, what are our chances of finding it? What are its chances of finding us?
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Last updated on 27 November 2011.
