Naked Eye Astronomy The Cycles of the Sun Summer Winter The Sun (and everything else) rises in east and sets in west At noon (in the northern hemisphere) it passes to the south The angle it is at highest in the summer and lowest in the winter This is responsible for the seasons Seasons are not caused by changes in the Earth-Sun distance Summer Winter 2. What Causes Seasons?

The Cycle of the Stars Constellations The Stars rise in the East and set in the West They go around slightly faster than the Sun Complete a cycle in one sidereal day – 23 hours 56 minutes It looks like the stars are rotating uniformly around us on a sphere – the celestial sphere In fact, this motion is caused by the Earth rotating once every sidereal day Constellations Patterns in the heavens are given names – constellations Originally these were associated with mythological stories We now name portions of the sky after these

Prof. Carlson Beats Up on Astrology The Sun vs. the Stars Compared to the background stars, the Sun follows a circle in the sky called the ecliptic Over the course of the year, the Sun passes through thirteen constellations – the basis of Sun-sign Astrology Sun completes its apparent journey in 365.25 days – one year The actual cause of this apparent motion is the motion of the Earth around the Sun Prof. Carlson Beats Up on Astrology Only 12, not 13 constellations are used: Ophiuchus is omitted The correspondences are nearly 2000 years out of date Scientific tests have failed to confirm the claims of astrology

The Cycles of the Moon New First Quarter Third Quarter Q. 3: How Often is the Moon Full? Full Entire cycle repeats every 29.5 days

The Cycles of the Moon The Moon is illuminated by the Sun The Moon is a sphere, not a flat disk The Moon goes around the Earth, in the same direction the Earth spins The Moon is much closer to the Earth than the Sun is

Solar Eclipses Q. 4: Types of Solar Eclipses