Transcript Ch 18.1 Astronomy-The Original Science

Ch 18.1 Astronomy-The Original Science
Part 1
When you finish this section you will be able to
1. Identify the units of a calendar
2. Evaluate calendars from different ancient
civilizations
3. Explain how our modern calendar developed.
4. Summarize how astronomy began in ancient
cultures and developed into a modern science.
Ch 18.1 Astronomy-The Original Science
• Astronomy is the study of all physical objects beyond
the Earth.
• Before astronomy became a science, people in ancient
cultures used the seasonal cycles of celestial objects to
make calendars and organize their lives.
• Over time, some people began to observe the sky for
less practical reasons – mainly to understand Earth’s
place in the universe.
• Today, astronomers all over the world are using new
technologies to better understand the universe.
The Stars Keeping Time
• Calendars are based on movements of objects in the
sky.
• A calendar is a system for organizing time within a
single unit called a year.
• A year is the time required for the Earth to orbit the sun
once. Within a year are smaller units of time called
months.
• A month is roughly the amount of time required for the
moon to orbit the Earth once. Within a month are even
smaller units of time called days
• A day is the time required for the Earth to rotate once on
its axis.
Ancient Calendars
• Ancient cultures based their calendars on different
observations of the sky
a) Ancient Mayan cultures had a very complex
calendar system that linked cycles of the sun,
the moon and Venus.
b) Ancient Chinese cultures made calendars as
early as the 14th century B.C. (3600 years ago)
based on the moons phases and positions in the
sky
Chinese star map
c) Ancient Egyptian cultures based their
calendar on the sun, with twelve 30-day
months and one 5-day month at the end ofthe
year.
d) Ancient Hebrew cultures based their
calendar on the moon and the sun. The
number of months in their calendar
alternated each year between 12 and 13
months.
Toward a Modern Calendar
• The early Roman calendar had exactly 365 days in a
year and 7 days a week, which worked well at first, but
gradually started shifting away from their original
positions in the year.
• It was then determined that there were 365.25 days in a
year which was corrected every four years by adding
one extra day to the fourth year.( this day was not taken
away the next year)
• We call this fourth year with the extra day a leap year.
• This calendar was known as the Julian Calendar
• In the Mid 1500s It was calculated that a year is only 365.242 days
long
* A new calendar was created called the Gregorian calendar
* This calendar is very much like the Julian calendar but it does not
keep the extra day.
• When this change was made Pope Gregory had to reduce the
calendar by 90 days to get it back to 365 days
• Scientist estimate that this calendar will remain accurate for another
3000 years
Ch 18.1 Part 2
When you finish this section you will be able to
1. Identify the units of a calendar
2. Evaluate calendars from different ancient
civilizations
3. Explain how our modern calendar developed.
4. Summarize how astronomy began in ancient
cultures and developed into a modern science.
Early observers- The Beginnings of Astronomy
• Nabta: The earliest
record of astronomical
observation (6000 to7000 years
ago)
• Stonehenge: Ancient
rock structure in southern
England used to follow
the seasons.(3000B.C.)
• The Babylonian: 700
B.C. precisely tracked the
positions of planets and
the moon which enabled
them to make an
accurate calendar.
• The Chinese: 1000B.C.
could predict eclipses and
had named 800 stars by
350 B.C.
• The Greeks: Were the
first to make astronomy a
science. They calculated
the size of the Earth,
moon and sun as well as
their distances from each
other
• The Maya: Used a
complex system of
mathematics and
astronomy
• The American Indians: Built huge Earth works to record
the four seasons which include the Vernal Equinox and
Summer Solstice.
• Ancient Arabs: Named many of the stars which still
have Arabic names.
Early Astronomers
• Ptolemy: (Greece) - Said that the Earth was the center of the
universe and that all objects revolved around it.
• Copernicus: (Poland) – Claimed that all objects in the solar
system revolve around the sun.
• Tycho Brahe: (Denmark) – Used several large tools to
observe the sky and took very accurate measurements of the
planets motion. Believed in the Ptolemy veiw if the universe
• Johannes Kepler: (Denmark) – Took Brahe accurate
measurements and developed new laws of planetary motion which
supported Copernicus view of the solar system
• Galileo Galilei: (Italy) 1st to use telescope and proved that
planets are celestial bodies not just dots of light, Favored
Copernicus view.
• Issac Newton: (England) Discovery of gravity and
development on the laws of motion helped explain and prove
Copernicus theory is correct.
Modern Astronomy
• Today computers and
telescopes are linked together.
• Computers not only control
telescopes, but they also
process the information
gathered by the telescopes so
that astronomers may better
analyze it.
• Better telescopes on earth and
in space allow us to study
objects both near and far.