Study Guide Answers

1. What is the difference between geocentric and heliocentric?

• Geocentric: Earth is the center of the universe

• Heliocentric: Sun is the center of the universe. This

is what we currently believe in!

2. What did Copernicus believe about the system of planets?

1)Found evidence for the idea of a heliocentric system.

2)Said that the moon revolved around the earth.

3)The earth revolved around the sun to cause a year.

3. What did Ptolemy believe about the system of planets?

He believed that the EARTH was at the center and the

sun & planets revolved around in

GEOCENTRIC

4. What did Brahe and Kepler prove?

Brahe: First to predict that orbits were not circular.Kepler: Assistant, He used Tycho’s data to figure out that the planets’ orbits are not round but are ellipses.

5. What discoveries did Galileo make that supported Copernicus’ views of the solar system? And what did he use to make these discoveries?

• One of the first to turn the Telescope to the sky to study astronomy.

• Saw that Venus went through phases like the moon – indicating change in angle like moon phases.

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Galileo improved the telescope to look at the sky. He discovered:• Venus goes through phases like the moon.• He saw that Jupiter had 4 moons revolving

around it.Galileo’s evidence convinced others that Copernicus’ ideas were correct.

6.  What two forces keep the planets in orbit around the sun?

Inertia &

Gravity

7. What is the difference between inertia and gravity? What would happen if one or the other was not present?

Inertia: The tendency of a moving object to continue in a straight line or a stationary object to remain at rest. Moon would crash

Gravity: The force of attraction between objects - the force depends on the mass of the two objects and the distance between them. Moon would float away

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Without gravity, the planets would fly off into space.

Without inertia, the moon would fall to Earth, or the planets to the sun.

8.  List the planets in order from the sun out.

MercuryVenus Earth Mars

Jupiter SaturnUranus Neptune

9.  What do the first 4 inner planets have in common

They are small, and have rocky surfaces

Not as much Hydrogen and Helium because they are

closest to the sun.Mercury, Venus, Earth, Mars

10.  What do the first 4 outer planets have in common

Gas Giants They are much larger than Earth and do not have solid

surfaces.The gas can’t escape because

these planets have very STRONG GRAVITY

Jupiter, Saturn, Uranus, and Neptune

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• They are made of gas.• They have deep atmospheres held

by strong forces of gravity.• They are very large.• They have rings.• They have more than two moons.

11. What makes Earth unique and different from the other planets?

• Liquid water. • A protective atmosphere.

12.  How are Venus and Earth alike?

Relatively the same size and density

13. What is the difference between a comet, asteroid, and meteoroid?

Comet: small body of ICE, rock and cosmic DUST that follows a narrow, elliptical orbit around the sun; gives off gas and dust in the form of a tail when it passes close to the sun.Asteroid: small, rocky object that orbits the sun, usually in a band between Mars and Jupiter.Meteoroid: a relatively small body, rocky body that travels through space.

14. What is the difference between meteoroid, meteor, meteorite?

Meteoroid: a relatively small body, rocky body that travels through space. They are smaller than asteroids, and can be as small as a speck of dust.Meteor: “shooting star” a bright streak of light cause by a meteoroid burning in the atmosphere.Meteorite: when a meteor makes it to Earth’s surface.

15. Comets’ orbits are what shape?

Comet’s orbits are long, narrow ellipses.

16. What affects the revolution time of each planet?

According to Kepler’s third law of planetary motion, “The farther away from the sun a planet is, the longer it takes for the planet to orbit the sun.”

17. Which object or objects would have the greatest period of revolution?

A comet.

18.  What is the asteroid belt and where is it located?

wide region of small, rocky bodies that is located

between the orbits of Mars and Jupiter

19. What is the theory that explains the formation of our solar system? Explain the theory.

The theory that explains the formation of our solar system is the Nebular Theory.Scientists believe that the solar system was formed when a cloud of gas and dust in space was disturbed, maybe by the explosion of a nearby star (called a supernova). This explosion made waves in space which squeezed the cloud of gas and dust. Squeezing made the cloud start to collapse, as gravity pulled the gas and dust together, forming a solar nebula. Just like a dancer that spins faster as she pulls in her arms, the cloud began to spin as it collapsed. Eventually, the cloud grew hotter and denser in the center, with a disk of gas and dust surrounding it that was hot in the center but cool at the edges. As the disk got thinner and thinner, particles began to stick together and form clumps. Some clumps got bigger, as particles and small clumps stuck to them, eventually forming planets or moons . Near the center of the cloud, where planets like Earth formed, only rocky material could stand the great heat. Icy matter settled in the outer regions of the disk along with rocky material, where the giant planets like Jupiter formed. As the cloud continued to fall in, the center eventually got so hot that it became a star, the Sunhttp://www.windows.ucar.edu/tour/link=/our_solar_system/formation.html

20. How old is our solar system?

About 4.6 billion Years

21. What two elements is our solar system mainly composed of?

Hydrogen &

Helium

22. Which planet’s atmosphere is trapping carbon dioxide and causing the Greenhouse Effect?

Venus is the hottest planet in the solar system because its carbon monoxide atmosphere traps the heat from the sun.

23. Which other planet is believed to have once had running water and has been shaped by the same forces as Earth? List the forces that have and continue to shape Earth’s surface.

Scientists believe that Mars once had running water.The forces that shape Earth’s surface are weathering, erosion and deposition.

24. List each astronomer and their contribution to modern astronomy.

Ptolemy: Geocentric theoryCopernicus: Heliocentric theoryBrahe: 20 years of accurate observations and measurements.Kepler: with Brahe’s data discovered orbits are elliptical. Laws of planetary motion.Galileo: with his telescope proved Copernicus was correctwhen he saw the phases of Venus and the moons of Jupiter.Newton: discovered gravity and inertia, which explained why planets remain in their orbits.