Download ecliptic

August 26 – 10am Class
• Turn in HW 1 if you didn’t turn it in on Wednesday
• On line quiz #1:
•Go to d2l and click on “Quizzes”
Open book, notes, anything, but do not talk to
other students
No time limit
Unlimited number of attempts
Graded automatically on d2l
Will start Saturday morning at 8am
Finish before the beginning of class next Friday
Key will be posted after class next Friday.
Lascaux Cave Paintings:
Cro-Magnons recorded the lunar cycle
15,000 years ago
http://news.bbc.co.uk/2/hi/science/nature/975360.stm
PATTERNS IN THE SKY
• Ancient peoples observed the Sun and stars
and created calendars that marked the yearly
passage of time
• Earth rotates on its axis once every 24 hours
• Earth revolves around the Sun once every 365
days
• The stars appear to rise in the east and set in
the west every night, on a big dome called the
celestial sphere.
Celestial Sphere and Constellations
The sky is divided into 88 "official" constellations, although in reality the stars
in any particular constellation are at different distances from Earth.
Ancient Egyptian celestial sphere:
the goddess Nut (“noot”) c. 3000 BC
Nut gave birth to the Sun god “RA” every morning
Hebrew Cosmology
And God said, “Let there
be a vault in the midst
of the waters, and let
it divide water from
water.” And God made
the vault and it
divided the water
beneath the vault
from the water above
the vault, and so it
was. - Genesis 1:6
Michaelangelo’s depiction of the creation
Of the planets and stars
God had divided the waters "above" from the waters "below" by constructing an
immense dome that held open the space for dry land.
In the Hebrew Bible the dome is called "raqi'a," meaning a firm substance, and
rendered in the King James translation as "the firmament”
The firmament in Biblical times was understood to be firm only by the will of God.
If God were angered, "the windows of heaven"
and "the fountains of the deep” could burst
open once again and those lovely blue waters
would destroy the Earth.
A painting by the American
Edward Hicks (1780–1849),
showing the animals boarding
Noah's Ark two by two.
• The orbital path of the Earth around the Sun is called the ECLIPTIC.
• The Earth’s axis of rotation is tilted 23 ½ degrees with respect to the
ecliptic plane.
The orbit of the Earth around the Sun
is not a circle; it is an ellipse
The Earth's rotation is counter clockwise looking down on the N pole, and results
in the apparent motion of the celestial sphere -- everything rises in the East and
sets in the west.
1 solar day = time from one noon to the next
= 24 hours
Longitude and Latitude
Longitude and latitude define your position on Earth.
The zero of latitude is the Equator
The zero of longitude is the prime meridian: line which passes through
the old Greenwich observatory outside London, England.
Tucson: Latitude 32 degrees North, Longitude: 110 degrees west
Astronomers define DECLINATION (Dec) and Right Ascension –
these are coordinates like longitude and latitude but describe the position of
stars, galaxies, etc on the celestial sphere.
At the north pole of Earth:
Figure 2.4: As viewed from the Earth’s North Pole
Figure 2.3: The celestial sphere as a useful fiction
Circumpolar Stars
Always above
Horizon
In the Northern
Hemisphere, they
Appear to rotate
around
The North Star,
Polaris
In the Southern
Hemisphere,
No bright star at
rotation center
Figure 2.5: Our perspective on the sky depends on our location
Figure 2.9, Right: Celestial sphere at different latitudes
• The orbital path of the Earth around the Sun is called the ECLIPTIC.
• The Earth’s axis of rotation is tilted 23 ½ degrees with respect to the
ecliptic plane.
Figure 2.10: Earth’s orbit and constellations along the ecliptic
The Zodiac = The constellations along the ECLIPTIC
Astrology and Horoscopes:
• Assumption is that the position of the Sun and planets at the exact
moment of your birth determines what will happen in your life.
• Horoscopes: very general statements that can apply to anybody.
What is the probability that 1/12 of the world’s people are
having the same kind of day?
• Different schools of astrology contradict each other.
Superstitions:
Thinking that one action causes another when there is no
actual connection
c.f. B.F. Skinner’s pigeons and “pigeon religion”