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PCS 181
Margaret Buckby

Currently these notes cover: a brief overview of astronomy's place in the scientific endeavor, the philosophy of science and the scientific method, astronomy that can be done without a telescope, a history of astronomy and science, Newton's law of gravity and applications to orbits, Einstein's Relativity theories, electromagnetic radiation, telescopes, all the objects of the solar system, solar system formation, determining properties of the stars, the Sun, fusion reactions, stellar structure, stellar evolution, the interstellar medium, the structure of the Milky Way galaxy, extra-galactic astronomy including active galaxies and quasars, cosmology, and extra-terrestrial life. This site also has pages giving angular momentum examples, a quick mathematics review, improving study skills, astronomy tables, and astronomy terms. All of the line drawings were done with Create on my old NeXT machine or with Freehand on a wintel laptop and Macintosh at home. The line art images on the screen are GIF and PNG images. If you have comments about these notes, please email me. Some significant updates since the major 2010 revision are listed below in the chapter descriptions. There are other tweaks not listed on this homepage. Contents (chapters + descriptions): 1. Astronomy as a Science and a Sense of Scale. I introduce astronomy's place in science, and give a sense of the size and time scales involved. Section on astrology expanded. A separate section about the Science-Religion interface and interaction is available on this site. It is not part of the regular textbook. I take a middle road between the fundamentalists on both sides of the "debate"/dialogue. 2. Method for Finding Scientific Truth. Borrowing from Pine's book ``Science and the Human Prospect'' I discuss the scientific method, correlations, problem of induction, positivism, levels of testimony, empiricism, models correspondence with reality. Pseudoscience vs. science article. Borrowing from Carl Sagan's "The Demon- Haunted World", I take up the subject of UFOs as alien spacecraft. This article is not part of the regular textbook. 3. Astronomy Without a Telescope. I discuss the celestial sphere, motions of the Sun (solar and sidereal days, time zones, equation of time, and seasons), motions of the Moon (phases and eclipses), and planetary motions. May 20, 2012 annular eclipse. 4. History of Astronomy. I focus on the rise of modern science in Europe, from the ancient Greeks to Kepler. 5. Newton's Law of Gravity. Newton's laws of motion and his law of gravity are discussed. Applications of those laws (esp. gravity) are covered (e.g., measuring the masses of planets and stars, orbital motion, interplanetary trips, tides, etc.). 6. Einstein's Relativity. I discuss Einstein's Special Relativity and General Relativity theories. The concepts of spacetime and gravity as a warping of spacetime are introduced along with observational proofs of his theories. Section on observational proofs was updated with information about LIGO 7. Electromagnetic Radiation (Light). General properties of light, definition of frequency, spectrum, temperature. Light production: Continuous (thermal) spectra, emission lines, absorption lines and the Bohr model for the atom. Doppler Effect and why spectral lines must be used to measure the doppler shifts. 8. Telescopes. Covers refractors, reflectors, radio telescopes, light-gathering power, resolving power, interferometers, magnification, and atmospheric distortion such as seeing, reddening, and extinction. Section on radio telescopes was updated with information from my visit to NRAO at Green Bank. 9. Planetary Science. This chapter is an introduction to planetary science. I discuss the techniques astronomers use to find out about the planets, their atmospheres (what determines if an atmosphere sticks around; behavior of gases; what determines the surface temperature; atmosphere layers; the transport of energy; effects of clouds, mountains, and oceans; weather vs. climate and climate change agents with feedbacks; and appearance), their magnetic fields (the magnetic dynamo theory), and their interiors including the geological forces at work reshaping their surfaces. In a separate section I focus on a comparison between the atmospheres of Earth, Venus, and Mars and why they are now so radically different from each other (greenhouse effect, carbon cycle, runaway refrigerator, runaway greenhouse, etc.) Mars discussion now includes proofs for liquid water in past and sub-surface water ice. The Earth discussion now includes the role of plate tectonics in the carbon cycle, evidence for human contribution to the atmospheric carbon dioxide and to the observed global temperature rise. There are links to two flowcharts: a Earth-Venus-Mars comparison and a flowchart of the calculations involved in determining if an atmosphere sticks around for billions of years. I end the chapter with a discussion of the major moons in the solar system and ring systems. Updates include: how paleoclimate is measured, Snowball Earth evidence, Mars discoveries (including notes from January 2011 "Follow the Water" forum), meteorites from Mars, Titan and Enceladus discoveries, and clarifications in discussion of human-caused climate change. Beautiful Planet photo album of nature photography has imagery of mountains, lakes, streams, waterfalls, large trees, flowers, aurorae, other landscape images and some images of insects and frogs. Most images are from the western United States but some are also from eastern Australia and the aurorae are from Fairbanks, Alaska. National park photo sets include: Crater Lake, Bryce Canyon, Grand Canyon, Zion, Grand Teton, Yellowstone, Devils Tower, and Glacier. The rest of the album are from various beautiful places in the western United States and eastern Australia. Answers to Global Warming Skeptics is a separate section about the climate change debate going on among the general public. It is not part of the regular textbook. The section has been updated, including the latest "going down the up escalator" results. 10.Solar System Fluff. The basics of meteorites, asteroids, and comets are introduced and how they can tell us the ``when'' and the ``how'' of the formation of the solar system. At the end is an exploration of the other planetary systems. Updates on Comet Hartley discoveries, exoplanet discoveries including those from the Kepler mission and free floater exoplanets, potentially hazardous asteroids (plus new section on deflecting and using asteroids), meteorites from Mars, and early history of the solar system. Commentary on planet definition added and also meteor shower table now has meteor speeds. 11.Determining Star Properties. Notes for the properties of stars and how we determine them. Things like distances to stars, their masses, radii, composition and speeds. Also HR diagram, spectral types, and spectroscopic parallax. The dangers of selection effects and biased samples are also discussed with the application of finding what a typical star is like. 12.The Sun and Stellar Structure. This chapter covers: The Sun, interiors of stars, and nuclear fusion, neutrinos, the solar neutrino problem, and helioseismology. The concept of hydrostatic equilibrium is used to explain the mass-luminosity relation and the reason for the mass cut-off at the high and low ends. Brown dwarf discussion expanded. Asteroseismology section added. 13.Lives and Deaths of Stars. This chapter covers: stellar evolution (all nine stages) and stellar remnants (white dwarfs, neutron stars, black holes). 14.The Interstellar Medium and the Milky Way. This chapter covers: the dust and gas between the stars and how we use the 21-cm line radiation to map the Galaxy. Also, the structure of the Milky Way Galaxy, our place in it, and how we determine these things. The rotation curve and the existence of the dark matter halo, stellar populations, and the galactic center are also discussed. Updates include: new illustrations for determining the presence of dark matter and a report on detecting the new arm of the Milky Way. 15.Other Galaxies and Active Galaxies. This chapter covers: the characteristics of other normal galaxies, active galaxies, and finding distances to other galaxies (this includes the distance-scale ladder). Also, large-scale structure is covered (galaxy clusters and collisions and superclusters). The discussion of dark matter has been expanded. 16.Cosmology. This chapter covers cosmology: the study of the nature, origin, and evolution of the universe as a whole. The distance-scale ladder topic is dealt with in the Steps to the Hubble Constant document. I discuss Olbers' Paradox, the cosmic microwave background radiation, the fate of the universe (open or closed), dark matter, dark energy, inflation, and the cosmological constant. Update on determination of Hubble constant by Lemaitre. The discussion of dark matter has been expanded. 17.Life Beyond the Earth. This chapter covers: life zones (habitable zones), types of stars to focus on in the search for suitable planets, characteristics of life, evolution by natural selection, working definitions of life, the kind of planet where we think life would likely arise, bio-markers in exoplanet spectra, and finally the frequencies we use in the Search for Extra-Terrestrial Intelligence (S.E.T.I.). Updates include expanded discussion on the characteristics of life, new material on working definitions of life, evolution by natural selection, looking for habitable free floater exoplanets, updates on planets in multiple-star systems (including Alpha Centauri). MORE  1. ASTRONOMY The study of stars and space.  2. I. Earth’s Place in the Universe Planet Earth – a small dense rocky planet  3. 2. Our Solar System Earth is one of 8 planets that orbit the sun – an average yellow star. 3:47  4. The Planets Orbits of the planets and their relative distances. 3:41  5. 3. Milky Way Galaxy Our Sun/solar system is one of an estimated 180 billion stars making up this spiral galaxy  6. 4. Universe Our Milky Way Galaxy is one of billions of galaxies in an expanding universe  7. II. Models of the Universe Geocentric Model About 2000 years ago, the Greek astronomer, Claudius Ptolemy developed a detailed model of the universe based on the idea of revolving spheres.  8. E. Models of the Universe In this model of the universe, Earth was at the center, and all heavenly bodies moved around Earth in Perfect circles.  9. 3. Ptolemy’s Geocentric model, as illustrated on the next page, can be summarized as follows: Earth is located in the center and does not move. The stars are located on a transparent sphere that rotates once each day from east to west around Earth.  10. The Sun , the Moon and each planet are carried by separate spheres of different sizes. Each planet is located on an ―epicycle‖ that also rotates. This explained retrograde motion.  11. Retrograde Motion  12. d. This model was accepted for almost 1400 years because it explained celestial observations made from Earth and……… it seemed obvious. However – The geocentric model does NOT explain terrestrial (Earth) observations such as: The movement/rotation of a pendulum’s direction. The curvature of the paths of projectiles, winds & ocean currents.  13. B. Heliocentric Model In the 1500’s, a new model of the universe was proposed in a book by the Polish astronomer Nicholas Copernicus. In this model of the universe, the sun was the center. 2:08  14. B. Heliocentric Model Copernicus’ heliocentric model can be summarized as follows: The Sun is located in the center of the system and does NOT move. The stars are located on a stationary/unmoving transparent sphere. The sphere is a great distance from the sun. The planets , including Earth , move in circles around the sun. The Moon moves in a circle around Earth . Earth rotates on its axis from west toward east each day.  15. However….. Copernicus’ heliocentric model does NOT explain the apparent cyclic variations in the size of the Sun, and the cyclic variation in orbital speeds of the planets. This is because in the heliocentric model, the planets orbit the sun in perfect circles .  16. Brainstorming Rules Inspect the question Develop as many ideas as possible as quickly as you can. Stretch your thinking. Each idea should be new and different (think creatively and divergently), but you can build off of other’s ideas. All responses are acceptable. Do not JUDGE someone’s ideas. Work within the time limit (5 minutes).  17. STEPS Select a recorder Time limit is 5 minutes Recorder should record each idea as stated. One idea must come from each participant before proceeding to the next. You are encouraged to build on others’ ideas and generate as many possible within the time frame. Examine and group the responses according to their quality (Great, Good and Just OK). Present the BEST idea for solving the problem.  18. This animation shows twelve images of the sun, each taken through a telescope on Earth, one month apart. The dates range from August 2000 to July 2001. The dark markings on the sun are sunspots—regions where the surface is slightly cooler than the surrounding area. Notice how the size of the sun appears to change in a regular pattern.  19. SO..The question is: Why does the size of the sun appear to change? Answer : All stars change size over their lifetimes, but the sun is currently very stable. Evidence indicates the sun has a constant diameter of about 1.4 million kilometers. The only reasonable explanation for the change in the sun's apparent size is that Earth's distance from the sun changes in a regular pattern.  20. C. Kepler’s Heliocentric Model In 1609, Johannes Kepler published a book which included his first 2 ―Laws of Planetary Motion‖. These laws explain why th
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