# Geocentric Model aka Ptolemaic Model

 Sana 11.10.2017 Hajmi 445 b.

• ## Ancient Greeks

• Earth is at the center of the Universe.
• The Earth stood still & never moved.
• Stars are on a separate sphere orbiting the Earth

## 7 objects moved differently in the sky known as the “wanderers” or planetai. Sun, Moon, Mercury, Venus, Mars, Jupiter & Saturn

• 7 objects moved differently in the sky known as the “wanderers” or planetai. Sun, Moon, Mercury, Venus, Mars, Jupiter & Saturn
• ## Ptolemy

• Designed an updated model of the geocentric model.
• The planets orbit in circles around the Earth & also travel in circles on the orbit.

• ## Nicholas Copernicus

• Earth revolves around the Sun.
• Moon revolves around the Earth.
• Earth rotates on an axis.
• Planets revolved around the Sun.
• Planets have circular orbits.

• ## Tycho Brahe & Johannes Kepler

• Brahe charted the motions of celestial bodies before telescopes.
• Mathematician Kepler used Brahe’s data to form the Laws of Planetary Motion:
• 1. The path of a planet around the Sun is an ellipse.

• ## Galileo

• Believed that objects fall to the Earth at the same rate despite the object’s weight.
• Air resistance slows down falling objects.

• ## Sir Isaac Newton

• Law of Universal Gravitation
• » Gravity is a force generated between two objects.
• » Gravity depends on the mass of each object & the distance between them.

• ## Albert Einstein

• Theory of General Relativity
• » Matter tells space how to curve.
• » Curved space tells matter how to move.
• » Everything moves in the straightest possible line in curved space-time.

• ## Distances in the Solar System

• Astronomical Units
• Distances in space are millions of miles/kilometers in the solar system.
• One astronomical units (AU) is the distance between the Earth & the Sun.
• 1 AU = 93 million miles = 150 million km

• ## Mercury

• .39 AU from the Sun
• Named after the Roman messenger god (Hermes)
• Covered in craters & cliffs, similar to the Moon.
• No true atmosphere; trace amounts of sodium & potassium.
• As cold as -170oC in the dark & as hot as 425oC in the light.

• ## Venus

• .72 AU from the Sun
• Named after the Roman goddess of love & beauty (Aphrodite)
• Thick atmosphere of CO2 which causes a severe greenhouse effect producing temperatures well over 400oC. (Hottest planet)
• Air pressure is 90 times greater than the Earth’s.
• Similar to Earth’s size.

## Has retrograde rotation (rotates backwards)

• Has retrograde rotation (rotates backwards)
• Takes longer to rotate than to revolve around the Sun. (Day is longer than its year.)
• Covered with inactive volcanoes.
• 3rd brightest object in Earth’s sky.

• ## Earth

• 1.0 AU from the Sun
• Also known as Gaia, Terra, or Home.
• More than 70% of Earth’s surface is covered in water.
• Only planet known to have life in existence.
• Has a natural satellite (Moon/Luna.)

• ## Mars

• 1.5 AU from the Sun
• Named after the Roman god of war (Ares)
• Iron oxide (rust) in the soil gives it a reddish color.
• Polar ice caps made mostly of frozen CO2 (dry ice) & some water.
• Mars is half the size of the Earth.
• Global dust storms.
• Ranges from -125oC at night & 20oC during the day.

## Olympus Mons, the largest volcano in the solar system is on Mars.

• Olympus Mons, the largest volcano in the solar system is on Mars.
• Thin Martian atmosphere of Nitrogen & CO2
• Mars has two small moons (Phobos and Deimos) that came from the asteroid belt.

• ## Jupiter

• 5.2 AU from the Sun
• Named after the Roman king of the gods. (Zeus)
• Completely made of Hydrogen & Helium gas (gas giant)
• Largest of the solar planets.
• Swirling bands of rotating clouds in the upper atmosphere.

## Large rotating hurricane called the Great Red Spot. (2 Earth sizes)

• Large rotating hurricane called the Great Red Spot. (2 Earth sizes)
• 4 faint rings in orbit.
• 2.5 times greater in mass than all of the other planets combined.
• Has at least 63 natural satellites, 4 largest are known as the Galilean Moons.

## Ganymede

• Ganymede
• » Largest moon in the solar system (bigger than Mercury, but less mass.)
• » Covered with a crust of rock & ice that is heavily cratered.
• » Thin atmosphere of Oxygen.

## Callisto

• Callisto
• » 3rd largest moon in the solar system
• » Most heavily cratered object in the solar system.
• » Thin atmosphere of CO2.

## Europa

• Europa
• » Covered in a shell of ice
• » A deep ocean beneath the ice shell.
• » Thin atmosphere of Oxygen.

## Io

• Io
• » About the size of the Earth’s Moon.
• » Most volcanically active body in the solar system. Erupts sulfur.
• » Thin atmosphere of Sulfur dioxide.
• » No craters. Why?

• ## Saturn

• 9.6 AU from the Sun
• Named after the Roman god of agriculture. (Cronos)
• Made of Hydrogen & Helium (gas giant)
• Flattened poles from spinning very fast.
• Less dense than water.

## Most elaborate system of rings (rock & ice debris)

• Most elaborate system of rings (rock & ice debris)
• 14 or more rings.
• 56 or more natural satellites.

## Titan

• Titan
• » 2nd largest moon in the solar system.
• » Has a thick, dense atmosphere mostly of Nitrogen & some methane.
• » Surface is “squishy” & has lakes of liquid hydrocarbons.

• ## Uranus

• 19.2 AU from the Sun
• Named after the Greek god of the sky.
• Gas giant made of Hydrogen, Helium & methane.
• Rotates on its side.
• System of rings.
• 27 or more moons.

• ## Neptune

• 30.1 AU from the Sun
• Named after the Roman god of the sea (Poseidon)
• Gas giant made of Hydrogen, Helium, & methane. (the methane makes it blue)
• Near-supersonic & dynamic storms.
• Faint ring system.
• 13 known moons

## Triton

• Triton
• » Icy, rocky surface.
• » Coldest body in the solar system (- 37oC)
• » Icy volcanoes & geysers erupting Nitrogen, dust & methane

• ## Ceres

• 2.7 AU from the Sun
• Largest object in the asteroid belt (950km in diameter.)
• Classified an asteroid for over 150 years.
• It is believed to have a rocky core, icy water mantle, & a thin, dusty crust.

• ## Pluto

• 39.4 AU from the Sun
• Named after the Roman god of the underworld (Hades)
• Second largest dwarf planet in the solar system.
• Pluto’s companion, Charon , is half the size & doesn’t orbit around Pluto.
• Pluto & Charon are small enough to fit inside the United States.

• ## Eris

• 67.7 AU from the Sun
• Largest known dwarf planet in the solar system with a diameter of 2400km.
• At least one moon, Dysnomia.

• ## Other Possible Dwarf Planets

• Orcus
• Sedna
• Charon
• Possibly 43 others

• ## Comets

• Large chunks of frozen gases, rock & dust orbiting the Sun. (Dirty snowball)
• 1. Nucleus – main portion of the comet
• 2. Coma – thawed gases & dust form a bright cloud surrounding the nucleus.
• 3. Tail – solar winds push away the gases of the coma forming a blue ion tail & a yellowish-white dust tail.

## Famous Comets

• Famous Comets

## Comet Hale-Bopp

• Comet Hale-Bopp
• » Comet discovered by amateur astronomers.
• » Last seen Spring of 1997.

## Comet Shoemaker-Levy 9

• Comet Shoemaker-Levy 9
• » Broke into several pieces and collided with Jupiter in 1994.
• » They created several dark marks in the atmosphere that eventually disappeared.

• ## Asteroids

• Large chunks of rock material left over from the formation of the solar system.
• Most asteroids are found in the asteroid belt between Mars & Jupiter.

• ## Meteoroids, Meteors, & Meteorites

• Meteoroids are pieces of rock & dust left behind by orbiting comets.
• Small meteoroids that burn up in the Earth’s atmosphere are called meteors or “shooting stars.”
• Larger meteoroids that don’t burn up in the atmosphere and hit the Earth are called meteorites.