Observations of the sky Observations of the Sky  What patterns, motions, and events do we notice in the sky?  What theories can we create to explain them?  How can these theories be tested?

Observations of the sky WHAT DO YOU THINK? 1. Is the North Star—Polaris—the brightest star in the night sky? 2. How many zodiac constellations are there? 3. What causes the seasons? 4. Does the Moon have a dark side that we never see from Earth? 5. Is the Moon ever visible during the daytime? 6. What causes lunar and solar eclipses?

Observations of the sky Constellations Groupings of stars in the same direction Groupings of stars in the same direction Pattern repeats every year Pattern repeats every year OrionLeo

Observations of the sky 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

Time-lapse photo looking North! WHY???

Observations of the sky “Circumpolar” Constellations Some constellations always visible Some constellations always visible … and they rotate around Polaris … and they rotate around Polaris

Observations of the sky Finding your Latitude! The HEIGHT of Polaris indicates Latitude The HEIGHT of Polaris indicates Latitude Altitude angle

Observations of the sky How the sky moves at the north pole over time… Stars don’t set!

Observations of the sky How the sky moves at the equator over time… Stars set straight DOWN

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… … for *most* observers, but not all! … not always due East, nor due West! Rises in the East, sets in the West… … for *most* observers, but not all! … not always due East, nor due West! D Parkinson

Observations of the sky The Sun It takes about 24 hours to repeat It takes about 24 hours to repeat How it rises & sets depends on position! How it rises & sets depends on position! Near Equator, almost straight up/down Near Equator, almost straight up/down Near Poles, very “shallow” angle! Near Poles, very “shallow” angle!

Observations of the sky Seasonal Patterns Height of Sun varies over the year Height of Sun varies over the year It gets hot in summer, and cold in winter! It gets hot in summer, and cold in winter!

Observations of the sky Seasonal Patterns Summer: Summer: Sun higher in the sky, shining more DIRECTLY Sun higher in the sky, shining more DIRECTLY Sun up longer, more hours in the day Sun up longer, more hours in the day Winter: Winter: Sun lower in the sky, less direct light Sun lower in the sky, less direct light Sun not up as long Sun not up as long Does DISTANCE matter?? Does DISTANCE matter??

Observations of the sky Seasonal Patterns Sun’s “speed” across the sky varies Sun’s “speed” across the sky varies The “analemma” is famous… The “analemma” is famous… lower loop = Winter, Earth moves faster in its orbit Upper loop = Summer, Earth moves slower in its orbit

Observations of the sky Seasonal Patterns Bergamo, Italy Bergamo, Italy Photos by John Nystuen, University of Michigan

Observations of the sky Process of Science Example! Observations Observations Seasons! (hot, cold patterns that repeat yearly) Seasons! (hot, cold patterns that repeat yearly) Research Research Happens every year Happens every year Building Testable Theories & Hypotheses Building Testable Theories & Hypotheses Sun’s distance causes seasons? Sun’s distance causes seasons? Do the experiment Do the experiment Sun is closer in northern winter! Sun is closer in northern winter! Throw out the hypothesis! Revise the theory! Throw out the hypothesis! Revise the theory!

Observations of the sky Process of Science Example! More Observations More Observations Earth “tilts” towards polaris Earth “tilts” towards polaris More Research More Research degrees degrees Building Testable Theories & Hypotheses Building Testable Theories & Hypotheses Earth tilts “closer” to the sun to create summer? Earth tilts “closer” to the sun to create summer? Do the experiment Do the experiment Earth’s orbit is elliptical – still MUCH closer in Jan Earth’s orbit is elliptical – still MUCH closer in Jan Throw out hypothesis again! Throw out hypothesis again!

Observations of the sky Process of Science Example! STILL More observations! STILL More observations! Sun’s height changing, length of day varies Sun’s height changing, length of day varies Southern Hemisphere seasons reversed Southern Hemisphere seasons reversed Research Research Absorption of Solar Radiation Absorption of Solar Radiation Building Testable Theories & Hypotheses Building Testable Theories & Hypotheses Earth’s tilt creates seasons Earth’s tilt creates seasons Do the experiment Do the experiment Seasons on other tilted planets? Yes! Seasons on other tilted planets? Yes! Publish, continue the process…. Publish, continue the process….

Observations of the sky The planets Five objects move relative to the Zodiac Five objects move relative to the Zodiac Each does it differently, at different times but eventually, you can see a pattern. Each does it differently, at different times but eventually, you can see a pattern.pattern Tunc Tezel, apod031216apod031216

Observations of the sky The Moon A sequence of repeated phases over about a “moonth” 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 Precession changes direction Earth’s rotation axis points in the sky