Transcript Astronomy in Civilization and contributing scientists

Astronomy in
Ancient Civilization
In order to understand
the future, we must
look to the past
Astronomy impacted ancient
civilizations
The major driving force
in ancient astronomy
studies was SURVIVAL.
When will rainy/dry
season come? When
should crops be
planted/ harvested?
Navigation
Astronomy impacted ancient
civilizations
Egyptians
Huge temples and
pyramids were built to
have a certain
astronomical orientation.
The constellation Orion
represented Osiris, who
was the god of death,
rebirth, and the afterlife.
The Milky Way
represented the sky
goddess Nut giving birth to
the sun god Ra.
Astronomy impacted ancient
civilizations
Egyptians
The center of Egyptian civilization
was the Nile River, which flooded
every year at the same time and
provided rich soil for agriculture.
The Egyptian astronomers, who
were actually priests, recognized
that the flooding always occurred
at the summer solstice, which was
also when the bright star Sirius
rose before the Sun.
The priests were therefore able to
predict the annual flooding, which
made them quite powerful.
Astronomy impacted ancient
Mayans
civilizations
The Maya were extraordinarily good
astronomers, making observations
and recording the motion of the Sun,
the Moon, and the stars.
*Venus was very important to them
Prior to 36 B.C., this civilization in
southern Mexico and northern Central
America had begun to use a 360-day
year to produce a very accurate
calendar and measuring long intervals
of time.
The ancient Maya are also known for
having had the only known fully
developed written language of preColumbian America, and the most
advanced mathematics and
astronomy.
Astronomy impacted ancient
civilizations
Aztecs
The Aztec Sun Calendar is a
large round stone, 12 feet
across weighing in at 24 tons.
The calendar was three feet
thick as well, so it was not
small by any means.
The Sun Calendar took more
than 50 years to make, which
is quite impressive considering
the fact that the Aztecs did not
have a hammer and a drill to
use.
Astronomy impacted ancient
civilizations
Aztecs
The twenty calendar days in
the month are represented by
twenty things in nature and in
everyday life that the Aztec
people were familiar with.
According to ancient Aztec
astronomy, there were 365
days of the year but only 360
were accounted for, as five of
them were days for sacrifice.
Astronomy impacted ancient
civilizations
Europeans
STONEHENGE is perhaps
one of the best known sites
of ancient astronomical
pursuits.
It is located in Salisbury
Plain, England
It is an ancient stone circle
from the stone age
Researchers believe it was a
calendar or almanac
Its construction began
around 2800 bc and
continued until 1100 bc
Astronomy impacted ancient
civilizations
Native Americans:
The Big Horn Medicine Wheel in
Wyoming is similar to Stonehenge
in design
It was built by the Plains Indians
Its spokes align roughly with
solstices and equinoxes
Contribution of
Scientists
It is to them we owe our
thanks.
Contributing Scientists
Ptolemy
Around 140 ad, a Greek
astronomer named Claudius
Ptolemaeus (known today as
Ptolemy) constructed perhaps the
best geocentric model of all time.
Geocentric = Earth-centered
universe
It explained remarkably well the
observed paths of the five planets
then known, as well as the paths of
the Sun and the Moon.
However, to achieve its explanatory
and predictive power, the full
Ptolemaic model required a series
of no fewer than 80 circles.
Contributing Scientists
Copernicus
The Ptolemaic picture of the
universe survived for almost 13
centuries until a sixteenth-century
Polish cleric, Nicholas Copernicus
rediscovered Aristarchus’s
heliocentric (Sun-centered) model.
Copernicus asserted that Earth
spins on its axis and, like all other
planets, orbits the Sun. Not only
does this model explain the
observed daily and seasonal
changes in the heavens but it also
naturally accounts for planetary
retrograde (backward) motion and
brightness variations.
Contributing Scientists
Copernicus
The critical realization that
Earth is not at the center of the
universe is now known as the
Copernican revolution.
Copernicus’s ideas were never
widely accepted during his lifetime.
By relegating Earth to a noncentral place within the solar
system, heliocentricity contradicted
religious doctrine of the Roman
Catholic Church.
His book On the Revolution of the
Celestial Spheres was not
published until 1543, the year he
died. Only much later did the
Copernican theory gain
widespread recognition.
Contributing Scientists
Galileo
Having heard of the telescope
invention (but without having seen
one), Galileo built a telescope for
himself in 1609 and aimed it at the
sky. What he saw provided much
new data to support the ideas of
Copernicus.
He revolutionized the way science
was done, so much so that he is
now widely regarded as the father
of experimental science.
Contributing Scientists
Galileo
Discovered that:
The Moon has mountains, valleys, and craters—terrain in
many ways reminiscent of that on Earth.
The Sun has imperfections—dark blemishes now known as
sunspots. By noting the changing appearance of these
sunspots from day to day, Galileo inferred that the Sun
rotates, approximately once per month.
Four small points of light, invisible to the naked eye, orbit the
planet Jupiter. He realized that they were moons, circling
that planet just as our Moon orbits Earth. Clearly, Earth was
not the center of all things.
Venus shows a complete cycle of phases, This finding
can be explained only by the planet’s motion around
the Sun.
Contributing Scientists
Galileo
In 1610 Galileo published his findings and conclusions supporting
the Copernican theory, challenging both scientific orthodoxy and
the religious dogma of the day.
In 1616 his ideas were judged heretical. Both his works and those
of Copernicus were banned by the Church, and Galileo was
instructed to abandon his astronomical pursuits. This he refused to
do and instead continued to amass and publish data supporting the
heliocentric view. These actions brought Galileo into direct conflict
with the Church.
The Inquisition forced him, under threat of torture, to retract his
claim that Earth orbits the Sun, and he was placed under house
arrest in 1633. He remained imprisoned for the rest of his life.
Not until 1992 did the Church publicly forgive Galileo’s “crimes.”
Contributing Scientists
Kepler
At about the time Galileo was becoming
famous for his telescopic observations,
Johannes Kepler, a German
mathematician and astronomer,
announced his discovery of a set of
simple empirical (based on observation) laws
that accurately described the motions of
the planets.
While Galileo was the first “modern”
observer, who used telescopic
observations of the skies to confront and
refine his theories, Kepler was a pure
theorist. He based his work almost entirely
on the observations of another scientist (in
part because of his own poor eyesight).
Contributing Scientists
Kepler
Kepler’s First Law has to do with the
shapes of the planetary orbits:
The orbital paths of the planets are
elliptical (not necessarily circular).
An ellipse is simply a flattened circle.
The eccentricity of an ellipse is basically
its flatness (Larger # = more oblong)
A perfect circle’s eccentricity is zero.
Two of the most important points of orbit
are the planet’s perihelion (its point of closest
approach to the Sun) and its aphelion (greatest
distance from the Sun).
Contributing Scientists
Kepler
Kepler’s Second Law addresses the
speed at which a planet traverses different parts of
its orbit:
An imaginary line connecting the Sun to any
planet sweeps out equal areas of the ellipse in
equal intervals of time.
While orbiting the Sun, a planet traces the arcs
(labeled A, B, and C) in equal times. When a
planet is close to the Sun, it moves much
faster than when farther away
Orbit time
A=B=C
These laws are not restricted to planets. They
apply to any orbiting object.
Contributing Scientists
Tycho Brahe
Kepler based his work almost entirely
on the observations of Brahe.
Those observations, which predated
the telescope by several decades,
had been made by Kepler’s employer,
Tycho Brahe, arguably one of the
greatest observational astronomers
who ever lived.
Tycho’s observations made with the
naked eye were of very high quality.
Contributing Scientists
Isaac Newton
He had one of the most brilliant minds
the world has ever known.
Legend has it that seeing an apple fall
gave Newton the idea that the same
force that keeps us bound to the Earth
also controls the motion of planets
and stars.
Newton's contributions to science
include the universal law of gravitation
and the development of calculus.
He is also famous for his book, Principia
Mathematica, in which he presents three
laws of motion….
Contributing Scientists
Isaac Newton
Three Laws of Motion:
Newton’s First Law:
An object at rest remains at rest and a moving object continues to move
forever in a straight line with constant speed until a force acts on it.
Newton’s Second Law:
The acceleration of an object is directly proportional to the net applied force
and inversely proportional to the object’s mass.
Formula: a = F/m
Newton’s Third law:
Forces always occur in pairs—if body A exerts a force on body B, then body B
exerts an equal force on body A, but oppositely directed. (For every force
there is an equal and opposite force)
Contributing Scientists
Albert Einstein
In 1905, Einstein presented his Special
theory of Relativity, which made bold
statements about the nature of light and the
equivalency of matter and energy.
Later, in 1916, he presented General
Relativity, on the link between gravity and
space and time, which were verified three
years later. Einstein also studied the
properties of elementary particles and
warned of the dangers of nuclear war.
"I know not with what weapons World War III
will be fought, but World War IV will be
fought with sticks and stones."
Contributing Scientists
Edwin Hubble
Hubble’s Law
Hubble's extensive observations of galaxies
helped him develop the idea of an
expanding universe, which forms the basis
of modern cosmology.
He also identified a relationship between a
galaxy's speed and its distance, the ratio of
which is called Hubble’s Constant. A
project of the Hubble telescope, currently
exploring outer space, is to accurately
measure this constant.
The Hubble Constant is the speed at which
the universe is expanding.
Contributing Scientists
Women in Astronomy
Maria Mitchell was the first female professor of astronomy in
the United States. She discovered the Comet of 1847.
After Mitchell's death, a crater on the moon was named after her.
Henrietta Swan Leavitt is known for her 1904 discovery of a
type of variable stars named cepheid variables. Cepheid variables
are stars that go through cycles of brightness and darkness.
Henrietta found that when observing a cepheid variable in another
galaxy, she could relate the length of the brightness cycle to the
size of the star.
With this discovery, she was able to determine the distances
between stars and the Earth. Cepheid variables are referred to as
"astronomical yardsticks" as they make it easier to measure
distances within the universe.