Transcript GO 1_ Early Theorieso Of Space And Technology

How has our Understanding
of the Universe Evolved?
ASTRONOMY PICTURE OF THE DAY
Why do you think ancient people created
such extravagent stores about the
universe and space?
• Myths, folklore and legends
were used to explain what
ancient peoples’ observed in
the night sky
• First Nations believed the night
sky was a pattern on a great
blanket above (i.e. Ursa Major);
this guided their movements.
• See Fig. 1.1
1. What is a Model?
2. Why do we use
models to represent
Space?
Models of Planetary Motion
• As long as people have been watching the nightly show of
stars and planets, they have sought ways to explain it.
• First calendars were lunar, accurate for hunters, gatherers
and fishermen.
• Settled societies needed a more precise solar (Sun)
calendar to predict planting and harvesting time
• Figuring out the regular motions of the Sun and Moon with
the irregular patterns of the 5 orbiting planets was a
puzzle for thousands of years
• How did the Earth fit in???
Geocentric Model
• About 2000 years ago, Aristotle proposed a Geocentric,
or EARTH CENTRED model to explain planetary motion
Geocentric Model
• When you go outside at night and look up - what do you see?
• To explain why the distant stars didn’t move, Aristotle
hypothesized that they were attached to the outermost sphere
– like stars glued to a ceiling!
• His ideas were aided by
the math and geometry
of Pythagoras and Euclid.
Geocentric Model
• Although this model explained the phases of the moon, it
could not explain some observations like why do Mars,
Jupiter and Saturn loop backwards across the sky
• Geocentric Model
Heliocentric Model
• 1530 Copernicus made observations that led him
to conclude that the Sun was at the center and the
planets revolved around it (Copernican Model)!!
Heliocentric Model
• 1610 Galileo Galilei gave further proof
looking through a telescope.
when
• Wandering planets (retrograde motion)
made sense if they revolved around the sun.
• He also observed lunar mountains, moons orbiting Jupiter,
sunspots and phases of Venus with his telescope
• Which was not much stronger than binoculars used today
For Your Information:
• In 1614, Galileo was accused of heresy for his support of the
Copernican theory that the sun was at the centre of the solar
system. This was revolutionary at a time when most people
believed the Earth was in this central position. In 1616, he was
forbidden by the church from teaching or advocating these
theories.
• In 1632, he was again condemned for heresy after his second
was published. This set out the arguments for and against the
Copernican theory in the form of a discussion between two
men. Galileo was summoned to appear before the Inquisition in
Rome. He was convicted and sentenced to life imprisonment,
later reduced to permanent house arrest at his villa south of
Florence. He was also forced to publicly withdraw his support
for Copernican theory.
• Galileo’s discoveries added credibility to the Heliocentric
model, but it could not predict planetary motion accurately
• Johannes Kepler came up with the solution.
• By using detailed observations of the planets from Tycho
Brahe, Kepler discovered the planets moved in ELLIPSES not
circles. (Circles are too perfect to be likely)
Modern
Model of
the Solar
System
What technology was used to aid in the develop of
our understandings of the universe?
• Technology has been used for thousands of years to
measure time:
– Merkhet (Egyptians) to predict star motion
– Quadrant (Egyptians) to measure star altitude
– Astrolab (Arabian) to chart star positions
– Cross-staff (Gurson) 1300’s to measure the angle
between the moon and stars
– First optical telescope 1500’s
Discovery Continued . . .
• As lens grinding technology improved (think from my
parents records to your iPods) the telescopes became
more powerful.
• As our viewing ability got better, the vast distance
between objects in space became obvious.
– The Earth is only a small planet orbiting an average star
– The Sun is only one arm of the Milky Way.
– The Milky Way is only 1 of 20 local galaxies we have
looked into!
Distance and Time in Space
• Kilometers is too SMALL of a unit to measure the vast
distances in space!
• Astronomical unit (AU) used for local solar system distances.
– 1AU is the AVERAGE distance between the
center of the SUN and the EARTH
• Light-year used for interstellar and intergalactic distances.
– 1 light year is the distance light travels in a YEAR!
– Because the speed of light is 300,000 km/s in a
vacuum, a light years is about 9.5 trillion kilometers
– 9,500,000,000,000 kilometers!! Now that’s FAR OUT!!