1. Astronomy – an Historical Overview

2. What is Astronomy? Astronomy:
The scientific study of celestial bodies, space and the physical universe as a whole.
Celestial Bodies:
Collective term for the Sun, moon, and the stars

3. THE SUN The closest star to the earth
An atmosphere of glowing hydrogen gas
Energy comes from nuclear fusion reactions taking place between hydrogen atoms
Has an outer atmosphere called the corona that is visible only during solar eclipses
Has “sun spots” which are dark spots that are cooler regions
110 times the diameter of the Earth
Temp: °C (core)

4. The Planets Inner planets Mercury, Venus, Earth and Mars
Called “terrestrial planets” because of their rocky composite
Outer planets
Jupiter, Saturn, Uranus and Neptune
Composed of gases and have many moons and rings

5. WHAT ABOUT POOR PLUTO????
Pluto is a dwarf planet. A dwarf planet travels around, or orbits, the sun just like other planets. But it is much smaller.
Clyde Tombaugh discovered Pluto in He was an astronomer from the United States. Venetia Burney named Pluto that same year. She was an 11-year-old girl from England.
Pluto is not very big. It is only half as wide as Canada. Pluto is smaller than Earth's moon. This dwarf planet takes 248 Earth years to go around the sun. If you lived on Pluto, you would have to wait 248 Earth years to celebrate your first birthday. One day on Pluto is about 6 1/2 days on Earth.

6. Pluto is about 40 times farther from the sun than Earth is
Pluto is about 40 times farther from the sun than Earth is. Pluto is in an area of space called the Kuiper (KY-per) Belt. Thousands of small, icy objects like Pluto but smaller are in the Kuiper Belt.
NASA decided to send a spacecraft to fly close to Pluto. The spacecraft’s name is New Horizons. It is only about the size of a piano. New Horizons launched in January In summer 2015, New Horizons flew by Pluto and its moons. It took almost 10 years to travel that far from Earth!

7. Motion in space
Most motions in space are “APPARENT.” This means that they only SEEM to be happening.
Example: The rising and setting of the sun
The sun is actually NOT moving, but the Earth’s rotation makes it seem like it is.

8. There are two main models that have been accepted throughout history!
Models of the universe
There are two main models that have been accepted throughout history!
Some of the scientists that first proposed a model were Aristotle and Ptolemy. The ancient Greeks were very interested in Astronomy and proposed the first theory.

9. Geocentric model Geocentric means “Earth-centered”
Developed by Aristotle 2400 years ago using only the naked eye
He stated that the following bodies orbited the Earth: Moon, Venus, Mercury, Sun, Mars, Jupiter and Saturn. These are the Roman names that we use now. They originally had names that were from the Greek gods.

10. Planet names
Mercury (Hermes) is the god of commerce, travel and thievery in Roman mythology. The planet probably received this name because it moves so quickly across the sky.
Venus (Aphrodite) is the Roman goddess of love and beauty. The planet is aptly named since it makes a beautiful sight in the sky, with only the Sun and the Moon being brighter.
Earth (Gaia) is the only planet whose English name does not derive from Greek/Roman mythology. The name derives from Old English and Germanic. There are, of course, many other names for our planet in other languages.
Jupiter (Zeus) was the King of the Gods in Roman mythology, making the name a good choice for what is by far the largest planet in our solar system
Mars (Ares) is the Roman god of War. The planet probably got this name due to its red color. Jupiter was the King of the Gods in Roman mythology, making the name a good choice for what is by far the largest planet in our solar system.
Saturn (Cronus) is the Roman god of agriculture.
Uranus is the ancient Roman deity of the Heavens, the earliest supreme god.
Neptune (Poseidon), was the Roman god of the Sea. Given the beautiful blue color of this planet, the name is an excellent choice!
Pluto (Hades) is the Roman god of the underworld in Roman mythology. Perhaps the planet received this name because it's so far from the Sun that it is in perpetual darkness.

11. Geocentric Continued….
Aristotle’s model could account for MOST of the movement, but not for the occasional backward motion of Mars, Jupiter and Saturn
Ptolemy later accounted for this backward motion by stating that it was retrograde motion caused by epicycles
A more accurate model was still to
come!

12. The heliocentric model

13. Heliocentric model Proposed by Copernicus in the early 1500’s
He proposed the sun was fixed and the Earth orbited the Sun
He also proposed that the Earth was rotating and that stars moving across the sky was merely an illusion created by the rotating Earth
He withheld publishing his theories until he was on his death bed (likely scared of what the church would say) until his death bed in 1543.

14. Kepler was next!

15. More accuracy….
Kepler made the predictions of the model more accurate by suggesting that the orbits of the planets were ellipses, not circles
Now, Galileo!
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16. Galileo Galileo PROVED, Galieo SAW, Galieo REVEALED
It took the invention of the telescope to really drive astronomy research further. Galieo is responsible for the invention and used it to prove the heliocentric model
He was a devout Catholic
Published “The Starry Messenger” in 1610

17. Galileo vs the Catholic church
“The Bible tells us how to get to Heaven, not how the Heavens go.” – If Galileo had been more careful with his words, he may not have been in so much trouble as the church originally had no problem with his findings
The problem arose when it was seen that he was personally interpreting scripture, without the aid of the church

18. Pope John Paul II expressed regret in 1992 about how the Galileo affair was handled
The Heliocentric Model of the Solar System is still what we use today!