Transcript Lesson 2 - Celestial Sphere and Earths True Motions

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
Orion the Hunter
North Pole
Equator
South Pole
North Pole
Equator
South Pole
North Pole
Meridian
Equator
South Pole
North Pole
Meridian
Equator
South Pole
North Celestial Pole
Celestial
Sphere
Celestial
Equator
South Celestial Pole
NCP
Declination
CEq
Celestial
Meridian
SCP
Zenith
Local Sky
W
S
N
E
Horizon
NCP
Visible Half
of the Sky
N
Z
W
E
CEq
S
Below the
Horizon
SCP
Measuring
Latitude
Zenith
NCP
CEq
W
Latitude
S
N
E
Horizon
Z
NCP
Z
W
NCP
S
N
E
Z
NCP
Equator
North Pole
W
N
S
E
40º N Latitude
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
Zenith
Above Horizon for > 12h
NCP
Above Horizon
for 12h
Above Horizon
for < 12h
W
N
S
Never Rises
Never Sets
E
CEq
Differential Rotational Speeds
Arctic Circle
66.5º N: 666 km/h
Binghamton, NY
42º N: 1200 km/h
Equator
1670 km/h
Cepheus
Draco
Ursa Minor
Polaris
2000 AD
Thuban
2700 BC
Precession of the Equinoxes
North Ecliptic Pole
Precess Westward
2000 AD
North Celestial Pole
Rotate Eastward
North Celestial Pole
15000 AD
North Ecliptic Pole
Precession of the Equinoxes
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
Solar & Sidereal Days
T=24h
(Solar day)
Sun overhead
T=23h 56m 04s
(Sidereal Day)
One Earth rotation
Noon
Not to Scale
T=0h
September
June
December
March
NCP
4 Seasons
Autumnal
Equinox
Summer
Solstice
3rd
4th
2nd
Winter
Solstice
Vernal
Equinox
1st
SCP
CEq
NCP
Ecliptic
CEq
~23.5º
Obliquity of
the Ecliptic
SCP
NCP
Summer
Solstice
CEq
Winter
Solstice
SCP
NCP
Autumnal
Equinox
Summer
Solstice
CEq
Winter
Solstice
Vernal
Equinox
SCP
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
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
June 21: Summer Solstice
Northern Summer
Southern Winter
2000 Dec 21: Winter Solstice
2001 Mar 20: Vernal Equinox
Winter
Spring
Summer
Autumn
2001 June 21: Summer Solstice
2001 Sept 22: Autumnal Equinox
Summer
Autumn
Winter
Spring
Constellations provide evidence
that Earth Revolves around the Sun
March 1999: Sun in Pisces
Taurus
Pisces
Aries
June 1999: Sun in Gemini
Aquarius
Taurus
Capricorn
Gemini
Pisces
Aries
Aquarius
Capricorn
Gemini
Sagittarius
Cancer
Sagittarius
Cancer
Scorpius
Leo
Virgo
Leo
Libra
Virgo
September 1999: Sun in Virgo
Taurus
Aries
Pisces
Scorpius
December 1999: Sun in Sagittarius
Aquarius
Taurus
Capricorn
Gemini
Libra
Aries
Pisces
Aquarius
Capricorn
Gemini
Sagittarius
Cancer
Sagittarius
Cancer
Scorpius
Leo
Virgo
Libra
Scorpius
Leo
Virgo
Libra