Transcript Class 1: From Astrology to Astronomy

Astronomy: Watching
the Sky
A TCNJ CCS Program
Contents
• Class 1: From Astrology to Astronomy –The
history of looking up at the sky.
• Class 2: A Trip Through the Solar System –
Planets, Moons, and Comets. Oh My!
• Class 3: The Big Bang and the Universe –
The history of everything
• Class 4: Space Exploration– Spaceflight and a
visit to the planetarium.
In the beginning…
• The ancients
believed that the
sky was the realm of
the gods.
• They knew the sky
well. With no TV or
Internet there was
nothing else to
watch at night!
In the beginning…
• Define terms:
• Astrology : A belief
system that the positions
of the stars and planets
provide information
about personality,
human affairs, and other
earthly matters.
In the beginning
• Astronomy: the
scientific study of
celestial objects (such
as stars, planets,
comets, and galaxies)
and phenomena that
originate outside the
Earth's atmosphere.
Astronomy vs. Astrology
• Astronomy and Astrology
were largely the same
thing.
• Many cultures believed
that the heavens were the
realm of the gods who
controlled men destinies.
• Observing the heavens,
however, also had very
practical applications.
Ancient Astronomy Worldwide
• Many ancient cultures had a highly developed
art of astronomy.
• This included the Chinese, Arabs, Greeks,
Babylonians and Mayans.
Egyptian Astronomy
• Had a 360 day calendar
from earliest times.
• Used movement of stars
and sun to predict Nile
flood.
• Religious festivals timed
with moon, stars, sun.
• Temples built base on
alignment with sky.
Alignment with Sky
• Pyramids aligned
with Polaris, the
North Star.
• Temple Amun-Re
at Karnak has a
passage that is
only illuminated by
the mid-winter’s
rising sun.
Alignment
• The ancients noticed
that stars always rose
at the same point.
• Other objects like the
Sun and Moon would
vary with the time and
season.
• Monuments like
Stonehenge were built
aligned to certain days
of the year and could
act as calendars.
Sun, Moon & Planets
• Do not rise
and set at
the same
place over
each day.
• But the stars
do!
Demo
• Sunrise alignment and a tomb.
Egyptian Gods in the Sky
• Sun was the god Re
• Moon was Troth god of
wisdom.
Ancient Constellations
• A grouping of stars is a
constellation.
• Different ancient
cultures had different
constellations.
• The afterlife god Osiris
shares most of the
same stars with our
modern constellation
Orion.
Some Greek Constellations
• Capricorn (the goat) – Draco (the dragon)
What the Ancients Saw
• All noticed that the
stars seemed to be
fixed on a giant
sphere that turned
about the earth
(The “Starry Vault”)
• The sun and moon
moved across the
sphere on similar
path.
The Wanderers
• Another group of objects
moved across the sky in the
same path as the sun and
moon.
• These did not always move in
a consistent direction but
wandered forward and back.
• We call this objects planets
after the ancient Greek word
for wanderer.
Mars Sky Track
Hairy Stars
• Comets were planetlike objects with long
tails that appeared
at random times.
• They were often
associated with
important
(sometimes evil)
events (death of a
king, etc.).
Evil Omen
• In 1066 the
appearance of
Halley’s Comet was
considered an omen
of the death of
Harold II of England
who died at the
Battle of Hastings
later that year.
The Zodiac
• The constellations the sun, moon and planets
moved through were often considered special.
• Today we call this group the Zodiac.
The Zodiacs
• Different
cultures had
different
zodiacs
because their
constellations
were
different.
Greek Zodiac
• The Greek Zodiac has 12
constellations:
• Aries, the ram; Taurus, the bull;
Gemini, the twins; Cancer, the
crab; Leo, the Lion; Virgo, the
Virgin; Libra, the scales;
Scorpio, the scorpion,
Sagittarius, the archer;
Capricorn, the goat; Aquarius,
the water bearer; and Pisces,
the fish.
Greeks: Aristotle
• Aristotle believed
that the earth was
at the center of a
number of sphere’s.
• On the outermost
sphere were the
stars.
• Inner spheres
contained the sun,
moon and planets.
Geocentric System
• A planetary system
with Earth at the
center like Aristotle
proposed was
geocentric. The
Greek word geo
means “Earth.”
• Most ancient
astronomers used a
geocentric system.
The Greeks: The Almagest
• Around 100 BC Claudius
Ptolemy took Aristotle's
system and put math to it.
• He published this in a
massive book called the
Almagest.
• It was the authority for
astronomy for almost the
next 1000 years.
The “Wanders” Problem
• The old
geocentric
system had hard
time explaining
the motion of the
planets. How
could they make
these strange
loops?
Heliocentric Theory
• A few ancient scholars, however,
came up with the idea that the
Sun, not the Earth was the
center of the solar system (Such
as Aryabhata a 5th century
Indian astronomer).
• A planetary system with the sun
in the center is known as a
heliocentric system.
• From the Greek word Helios,
which means “Sun.”
Copernicus
• Around 1530 the Polish
scholar Nicholas
Copernicus published a
book On the Revolutions
of the Celestial Spheres
proposing a heliocentric
system.
• It was a much simpler
system then Ptolemy’s.
Retrograde Motion
• Because both
Earth & other
planets are orbiting
the Sun they can
appear to move
backwards.
Copernican Revolution
• Copernicus’ claim
was controversial.
• Man and Earth not
center of universe.
• Changed our
understanding of
man’s place in
universe.
Johannes Kepler
• One of the first
astronomers to
adopt and defend
Copernicus’ sun
centered system.
• Invented a basic
refracting
telescope.
Demo
• Kepler’s Laws of Planetary Motion
Kepler’s Laws of Planetary Motion
• Kepler discovered that
the length of their orbit
was a function of their
distance from the sun.
• He also realized that
planets did not move
in perfect circular
orbits, but ellipses.
Galileo Galilei
• Did not invent the
telescope.
• One of the first persons
to use it for astronomy.
• Vocal supporter of sun
centered system.
Galileo’s Accomplishments
• Discovered mountains
on the moon in 1610.
• Discovered four moons
of Jupiter in 1610.
• Discovered rings of
Saturn in 1610.
• Discovered sunspots in
1613.
Galileo and the Church
• The church found the sun
centered system “false
and contrary to
Scripture.”
• Galileo was warned not to
defend Copernicus’
system.
• He was put on trial and
forced to recant his ideas.
• He spent the end of his
life under house arrest.
Father of Modern Astronomy
• Has been called:
• Father of modern
observational
astronomy
• Father of modern
physics
• Father of Modern
Science
Legacy
• Stephen Hawking says, "Galileo,
perhaps more than any other
single person, was responsible
for the birth of modern science.“
• In 1992, Pope John Paul II
issued a declaration
acknowledging the errors
committed by the Church tribunal
that judged the scientific
positions of Galileo.
Newton’s Gravity
• Isaac Newton born on 4
January 1643.
• Gravity: Every object in
the universe attracts
every other object.
• The force is more
powerful with more mass
involved.
• The force weakens over
distance.
Law of Gravity
• We are 6 times heavier
on the Earth than the
moon because the
Earth is more massive
than the moon.
• If you weighed 100
pounds on Earth you
would be 16.6 pounds
on the moon and 236
pounds on Jupiter.
Gravity
• One of the
weakest forces in
nature, but also
one of the most
long range.
• Holds the planets
in orbit around
the sun.
Demo
• Gravity vs. Electromagnetism
Homework
• Read “Comet Halley: Harbinger of Death?”
for next class.
Group Work:
• Groups will work together to present on
these topic on February 1st.
– Mars: Is there a possibility of Life on Mars?
– What’s the Story with Pluto?
– How does a telescope work?
– What is SETI?