Transcript Intro to Astronomy

Intro to Astronomy
Through the early history of civilization, people made
observations about the night sky, sun, and moon.
They tried to explain what they were observing with
stories and folklore.
They believed that the sun and stars revolved around the
Earth.
The Greeks came up with the idea of a geocentric
universe. Meaning they thought everything revolved
around the Earth.
A Greek astronomer named Ptolemy (1400 CE) designed
a model of the universe which put the Earth at the center
and had the planets moving on small circles which
moved on larger circles.
Copernicus
Copernicus (1543)- Made observations which
led him to believe that the geocentric model
was not accurate.
His observations put the sun at the center and the planets
revolved around it in perfect circles.
In a heliocentric model the sun is placed in the center and the
planets revolve around it.
Planetary Motion
Galileo (1610)
Galileo used the newly invented “spyglass” to make observations
of the night sky. He discovered that Jupiter had moons that
orbited it. This led him to the conclusion that not all objects
revolved around earth.
While looking at Venus he noted that it always stayed near the
sun. He discovered that Venus goes through a series of phases
similar to the Earth’s moon. Venus would not have a full set of
phases if it circled the Earth. Therefore the geocentric model is
incorrect.
Tycho Brahe
Copernicus and Galileo correctly placed the
sun at the center of the planets but incorrectly
stated that the planets moved in perfect
circles.
Brahe continued his observations for another 20 years accurately
recording the positions of the planets with out a telescope! He
died in 1601
His assistant named Johannes Kepler continued TB’s work by
analyzing the planets’ orbits and mapped Mar’s orbit. He thought
the orbit was round but his calculations did not match up. He
discovered that the orbit must not be circular but an ellipse.
The Birth of Modern Cosmology
Astronomers had been debating for over a century about the nature of
the universe that we live in. They new that the Sun, is just one star in
a larger collection of stars in the Milky Way. They saw faint objects
outside our galaxy, but could not determine the distance of objects
beyond 100,000 light years away.
A light year is the distance it would take a beam of light to travel in
one year. The Milky Way galaxy is 100,000 light years across.
In 1919 Edwin Hubble was working as an astronomer in
California. He was using a telescope that was nearly 3 meters
across and discovered that there were objects millions of light
years away- and that these objects are other galaxies!!
Hubble’s Law
Perhaps the greatest contribution that Edwin Hubble made was that
all the distant objects he was observing were moving!
Not only were they moving, but they were all moving away from
one another as though they were all on the surface of a balloon that
was inflating. He made this discovery using something called the
Doppler effect also known as “red shift.”
The Big Bang Theory
Hubble’s discovery led to our understanding that the universe
is expanding. Like the leading edge of an explosion going
farther and farther out.
If you think about what would happen if you let the air out of
the balloon- or ran the “explosion” in reverse, it all would
have started at a single point. This concept led to the theory of
the “Big Bang.” The idea that the universe began at a specific
point in the past, and it has been expanding ever since!
This explosion formed sub atomic particles which led to the
formation of simple atoms like Hydrogen.
Large clouds of hydrogen formed and within them, stars
began to form.
Stars began to form star systems and galaxies.
The stars within the galaxies formed planetary systems
Since Galileo's time our knowledge of the solar system has
increased dramatically. In Galileo’s time only the planets Mercury,
Venus, Earth, Mars, Jupiter and Saturn were known.
Since then we have discovered three more planets as well as
asteroids and comets.
We are now discovering planets orbiting distant stars and
discovered black holes.