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Observations of the Sky What What patterns, motions, and events do we notice in the sky? theories can we create to explain them? How Observations of the sky can these theories be tested? WHAT DO YOU THINK? 1. 2. 3. 4. 5. 6. Is the North Star—Polaris—the brightest star in the night sky? How many zodiac constellations are there? What causes the seasons? Does the Moon have a dark side that we never see from Earth? Is the Moon ever visible during the daytime? What causes lunar and solar eclipses? Observations of the sky Constellations Groupings of stars in the same direction Orion Pattern repeats every year Observations of the sky Leo Constellations by familiar shapes & by definition of regions Observations of the sky Constellations as guides ! Observations of the sky Constellations in the Summer Observations of the sky Constellations in the Winter Observations of the sky Measuring the sky with angles… Observations of the sky Observations of the sky Time-lapse photo looking North! WHY??? Observations of the sky “Circumpolar” Constellations Some constellations always visible … and they rotate around Polaris Observations of the sky Finding your Latitude! The HEIGHT of Polaris indicates Latitude Altitude angle Observations of the sky Stars don’t set! How the sky moves at the north pole over time… Observations of the sky Stars set straight DOWN How the sky moves at the equator over time… Observations of the sky How the sky moves at a latitude like Hayward… Observations of the sky The Sun Rises in the East, sets in the West… D Parkinson … for *most* observers, but not all! … not always due East, nor due West! Observations of the sky The Sun It takes about 24 hours to repeat How it rises & sets depends on position! Near Equator, almost straight up/down Near Poles, very “shallow” angle! Observations of the sky Seasonal Patterns Height of Sun varies over the year It gets hot in summer, and cold in winter! Observations of the sky Seasonal Patterns Summer: Sun higher in the sky, shining more DIRECTLY Sun up longer, more hours in the day Winter: Sun lower in the sky, less direct light Sun not up as long Does DISTANCE matter?? Observations of the sky Seasonal Patterns Sun’s “speed” across the sky varies Upper loop = Summer, Earth moves slower in its orbit lower loop = Winter, Earth moves faster in its orbit The “analemma” is famous… Observations of the sky Seasonal Patterns Bergamo, Italy Photos by John Nystuen, University of Michigan Observations of the sky Process of Science Example! Observations Seasons! (hot, cold patterns that repeat yearly) Research Building Testable Theories & Hypotheses Sun’s distance causes seasons? Do the experiment Happens every year Sun is closer in northern winter! Throw out the hypothesis! Revise the theory! Observations of the sky Process of Science Example! More Observations Earth “tilts” towards polaris More Research Building Testable Theories & Hypotheses Earth tilts “closer” to the sun to create summer? Do the experiment 23. 5 degrees Earth’s orbit is elliptical – still MUCH closer in Jan Throw out hypothesis again! Observations of the sky Process of Science Example! STILL More observations! Sun’s height changing, length of day varies Southern Hemisphere seasons reversed Research Building Testable Theories & Hypotheses Earth’s tilt creates seasons Do the experiment Absorption of Solar Radiation Seasons on other tilted planets? Yes! Publish, continue the process…. Observations of the sky The planets Five objects move relative to the Zodiac Tunc Tezel, apod031216 Each does it differently, at different times but eventually, you can see a pattern. Observations of the sky The Moon A sequence of repeated phases over about a “moonth” Observations of the sky The “wobble” of Earth… Precession changes direction Earth’s rotation axis points in the sky Observations of the sky