Dr. Henry Throop / University of Colorado 15-Jun-2000 Astronomy 1110 Exam Review - Exam #1 History of Astronomy, Motions of the Sky, and the Terrestrial Planets --------------------------------------------------------------------- General information: The exam will consist of some multiple choice, some short answer, and a few longer thought questions. It will take the whole class period (95 minutes) on Friday, June 16. Things that we haven't discussed at all from the reading (e.g., celestial navigation) won't be on the exam. There's a lot of text there and no one can learn all of it in two weeks. You should be familiar with, understand, and be able to explain the concepts that we have gone over in class and in the homework. I'll give you all the formulas, numbers, and conversion factors that you'll need. A calculator might be helpful. Dates are like stamp collecting. You do not need to memorize Aristarchus' birthdate, but you should be able to reproduce the flow of history. The general emphasis will be conceptual: the multiple choice q's will be similar in style to those we've done in class, and the longer questions will be like those on HW #2. There will probably be a few calculations, shorter than those on HW #1. Both Rob & I will have office hours Thursday -- come on by. History of Astronomy -------------------- What were the Greeks trying to explain? Motions of the stars, the planets, sun & moon They took their data, and made models of it. Aristarchus (300 BC) -- used Parallax to suggest that stars were a long way away Eratosthenes (200 BC) -- determined that Earth was round (well & shadow in Syria) Ptolemy (150 AD) -- first decent, long-lasting model of the Solar System, used epicycles (circles on top of circles) to reproduce observed retrograde motions of the planets. Copernicus (1500) -- put Sun at center Brahe (1600) -- did accurate naked eye observations of planetary positions Kepler (1600) -- put planets on ellipses rather than circles; 3 laws describing motions Galileo (1600) -- Used telescope to look at Jupiter, find moons of it, find that things orbited other than the earth Newton (1700) -- Developed Physics, calculus, etc. to describe in universal and quantitative terms the motions in the solar system Since then, only a few minor changes to basic structure of Solar System (e.g., relativity) Physics of Astronomy -------------------- Newton's Three Laws of Motion Newton's Law of Gravity Gravity pulls _every_ particle in the universe together. Exact force between two bodies depends on their masses & distance, and nothing else. Kepler's Three Laws of Planetary Motion 3rd law: two forms of it. Use one for objects around the sun, or use other (universal version) for objects orbiting anything. Orbits Planets are in free-fall always falling toward the sun. Space Shuttle is in free-fall always falling toward the Earth. Atmospheres ----------- A thin layer (as heavy as a few meters more of rocks) of gas regulates almost everything that happens at the surface. Sun heats the _surface_, which heats the atmosphere -- thus, gets colder as you go higher up in an airplane, and further from surface Greenhouse effect: Atmosphere is transparent to _visible_ light, but opaque to _infrared_ light; thus, heat can't escape Runaway greenhouse effect: Planet heats up, causing more greenhouse gases into atmosphere, which heats it up more, which... until it gets super-hot. Runaway greenhouse collapse: Planet cools off, causing greehouse gases to condense out, which caused planet to cool off more, which... Earth is remarkably stable! The atmospheres of both Mars & Venus have runaway dramatically. Perhaps clouds, distance, or life help regulate our own Earth? Mercury/Moon: no atmosphere; must've been lost, since all planets probably start with roughly similar atmosphere. Probably too hot, too small. Greenhouse gases: major ones are water, carbon dioxide, methane Motions of the Sky ------------------ Phases of the Moon -- figure out what phase, what rise time, what set time, whether near eclipse, etc. Seasons -- caused by tilt of earth through its orbit North star -- Earth's north pole points to it What do the stars look like from different places on Earth? N. Pole Equator S. Pole Boulder Lines in the sky (Meridian, Ecliptic, etc) -- will not be on exam Surfaces -------- Behavior & form of thin (1 km) surface lets us probe the rest of the planet & its crust, lithosphere, mantle, & core Tectonics: Plate tectonics, uplift, continental spreading Volcanism: volcanoes, ash, lava, hot spots (hawaii) Erosion: Wind, Glaciers, Rivers Impacts: Craters. Smallest particles burn up in atmosphere Be familiar with what processes are most important on what planets. Numbers ------- Scientific notation (appendix A in book) How to use, and why Units (appendix A in book) Almost all measurements come with a unit (m, km/s, mph, ly, cm^3, etc.) for standardization. Unit conversion Light year: distance light travels in one year. Just a regular distance, nothing magical Astronomical Unit (AU): average distance between Sun & Earth Planets ------- Terrestrial Planets: general familiarity with basic history, location, size of them Jovian (Giant) Planets: Larger, spaced further apart, different composition than terrestrial planets (much larger atmospheres) All the planets orbit in ellipses, which are _almost_ circular All the planets orbit in same plane, same direction, with their N. Poles pointing mostly in the same direction. Some exceptions (Venus & Pluto spin backwards; Uranus tilted on its side). Architecture of the SS ---------------------- Differences in planets (geology and atmospheres) are determined by: Brightness (`albedo'): does it absorb or reflect light from the Sun? Distance from Sun: hot or cold? Size: is it round, or is it lumpy? Can it retain an atmosphere? Can it sustain tectonics and volcanism? Composition: Dense? Lightweight? Thick core? Differentiated? History and evolution. Each planet is an individual! Big Ideas --------- A good model needs to be testable and correct. Look with your eyes and describe what you see. Universal, simple laws like gravity govern much of the structure of the Universe.