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The Celestial Sphere. The Caracol at Chichen Itza. Built around 1000AD. The Mayans developed a very accurate calendar. They also placed special significance on Venus. Human Sacrifices were routinely performed to worship Venus. Name that constellation. Orion the Hunter. North Pole.
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The Caracol at Chichen Itza • Built around 1000AD. • The Mayans developed a very accurate calendar. • They also placed special significance on Venus. • Human Sacrifices were routinely performed to worship Venus
North Pole Equator South Pole The Celestial Sphere
Equator North Pole South Pole
North Pole Meridian Equator South Pole
Equator North Pole Meridian South Pole
North Celestial Pole Celestial Sphere Celestial Equator South Celestial Pole
NCP Declination CEq Celestial Meridian SCP
Zenith W S N Horizon E Local Sky
NCP Visible Half of the Sky N W E S Below the Horizon Z CEq SCP
Zenith NCP CEq W S N E MeasuringLatitude Latitude Horizon
Z Z NCP NCP Z W W NCP N S S N E E 40º N Latitude Equator North Pole
Evidence of Earth’s Rotation • Apparent Rotation of the Celestial Sphere • Star Trails • Cycle of Night and Day • Inertial Effects of Stuff on Earth • Coriolis Effect • Focault Pendulum • Precession of the Equinox
Apparent Rotation of the Celestial Sphere
Apparent Rotation of the Celestial Sphere
Zenith Above Horizon for > 12h Above Horizon for < 12h Never Rises NCP Above Horizon for 12h Never Sets W N S E CEq
Arctic Circle 66.5º N: 666 km/h Binghamton, NY 42º N: 1200 km/h Equator 1670 km/h Differential Rotational Speeds
Cepheus Draco Polaris Ursa Minor 2000 AD Thuban 2700 BC
Evidence of Earth’s Revolution • Sidereal Day vs. Solar Day • Seasons • Due to Earth’s tilt in combination with its Revolution about the Sun • Constellations and the Zodiak • As Earth revolves, different stars are visible at night
T=24h (Solar day) Sun overhead T=23h 56m 04s (Sidereal Day) One Earth rotation Noon Noon Solar & Sidereal Days T=0h Not to Scale
Seasons September June December March
NCP 4 Seasons Autumnal Equinox Summer Solstice 3rd 4th 2nd Winter Solstice Vernal Equinox 1st CEq Ecliptic SCP
NCP Ecliptic CEq ~23.5º Seasons Obliquity of the Ecliptic SCP
NCP Seasons Summer Solstice Ecliptic CEq Winter Solstice SCP
NCP Seasons Autumnal Equinox Summer Solstice Ecliptic CEq Winter Solstice Vernal Equinox SCP
Seasons Z Summer Solstice NCP Vernal & Autumnal Equinoxes CEq W Winter Solstice N S E
Z Summer Solstice NCP Vernal & Autumnal Equinoxes W Winter Solstice N S E Seasons CEq
1 KW/m2 1 KW/m2 1 m2 2 m2
Equinoxes: March 20 & Sept. 22 Spring and Fall
December 21: Winter Solstice Northern Winter Southern Summer