TOPIC 8 B OBJECTIVES
THE EARTH IN SPACE
1. Describe the geocentric and heliocentric models of the solar system, and evaluate which model provides the simpler explanation for the apparent motion of celestial objects.
The Geocentric model places the Earth in the center of the universe. In this model all celestial objects travel in perfect circles around the Earth. When actual planetary data is plotted on a diagram of this model it produces extremely complex orbital paths for the planets.
The Heliocentric model places the Sun in the center of the solar system. When planetary data is plotted on this model it produces a much simpler orbital path, ellipses, for the planets.
2 a. Tell the path of stars and planets as viewed from New York State.
Planets appear to change direction, speed, and the stars they travel with. This strange apparent motion is called retrograde. Stars appear to move in counterclockwise circles around Polaris.
b. Calculate the apparent rate of motion of celestial objects.
Celestial objects appear to move because of the Earth's rotation. It takes the Earth 24 hours to cover the 360o in one rotation. By dividing 360o by 24 hours you get a rate of 15o/hour.
3. Define constellations.
A group of stars which has been given a name.
4 a. Name and describe the shape of all natural orbits in our solar system.
All natural orbits are ellipses.
b. Describe the location of the primary focus.
The primary focus is the location where you will find the object that is being orbited around. For example when talking about the Sun and the Earth, the primary focus is where the Sun is.
5 a. Define eccentricity.
Eccentricity is a mathematical way of determining how flat an ellipses is.
b. Calculate eccentricity using the (ESRT).
The formula is on page 16 of the ESRT. When using this formula the answer is not label with units.
6. Give an explanation for the cyclic change in the apparent diameter of the moon, Sun, and planets.
Since all natural orbits are ellipses the revolving object is sometimes closer, perigee, and sometimes farther, apogee, from the primary focus. When the revolving object is closer it appears larger, giving it a larger apparent diameter.
7. Compare the speed of a satellite with its distance from the primary focus.
The closer the satellite is to the primary focus the faster the satellite will travel.
8. Determine how changing the distance between two objects and/or changing the mass of one or both of the objects will affect the force between the two objects.
While students do not need to be able to use the formula for gravitation attraction, it does outline the factors involved in determining the force of gravity. The formula is on page 16 of the ESRT. The greater the distance between two objects the less the gravitational attraction. The greater the mass of the objects the greater the gravitational attraction.
9. Analyze the Solar System Data Chart in the ESRT.
The chart they need to be able to read is on page 14 of the ESRT.
10. Compare the planets on our solar system in regards to temperature, surface characteristics, and atmosphere.
The farther a planet is from the Sun the lower it's average temperature. The inner planets, Mercury through Mars, plus Pluto has rocky cores. The other planets are much larger and are composed of gas. Mercury, Pluto and Mars have very thin atmospheres. Venus atmosphere is a hundred times denser than Earth's. Mars and Venus atmospheres contain a lot of CO2, which is missing from Earth's atmosphere. It is thought that living things have removed much of the CO2 from Earth's early atmosphere.
11. Explain why impact structures are much more obvious on the Moon, Mercury, and Mars than on Earth.
With little or no atmosphere there is very little if any weathering on these structures. This means when an impact crater forms it remains forever. Earth's atmosphere also prevents smaller meterors from reaching the surface of the Earth
12 a. Identify the unit used to measure distances in the universe.
In our solar system often astronomers use the unit A.U. or astronomical units. One A.U. is equal to the average distance between the Earth and the Sun, which is 93,000,000 miles. A unit used for more distant objects is light year. One light year is the distance light travels in one year. Light travels at 186,000 miles/sec, which means in one-year light travels about 5,800,000,000,000 miles.
b. Compare the distance of the Earth to the Sun and other stars in the universe.
The Sun is about 93,000,000 miles away. The next nearest star, Alpha Centauri, is about 4.5 light years away, or about 26,100,000,000,000 miles away. Our galaxy, the Milky Way, is about 100,000 light years across. The next closest galaxy which is similar in size to the Milky Way, Andromeda, is over 2,000,000 light years away
13 a. Define galaxy.
A galaxy is large island of stars in space. They can contain anywhere from a little under 10 million stars to trillions of stars.
b. Describe the shape of the Milky Way Galaxy and the position of our solar system within the galaxy.
The Milky Way Galaxy is shaped like a pinwheel. The Earth is located on one of the arms of the pinwheel.
14. Describe the Big Bang theory.
This theory speculates that all of the matter in the universe was originally in one ball. This ball was a little larger than our Sun. About 15 billion years ago the ball exploded sending matter in all directions at close to the speed of light. As the matter moved away from the explosion gravity caused islands of hydrogen gas to collect. These islands formed galaxies, stars and planets
15. List two pieces of evidence to support the Big Bang theory.
1) By analyzing the spectrum produced by distant galaxies astronomers have discovered they all produce a Doppler shift to the red. This supports an expanding universe.
2) Astronomers have detected radiation in all directions, which they feel is a result of the big bang.
16. Describe the Doppler shift in regard to movement of celestial objects.
When sources of electromagnetic energy approach it causes the wavelengths of the energy it is emitting to appear to shorten. This is known as a blue shift. When sources of electromagnetic energy move away from an object the wavelengths of the energy they are releasing appear to lengthen. This is known as a red shift.
17. Compare the age of the Earth and solar system to the universe.
It is felt that the solar system, including the Earth, is about 5 billion years old. The universe is felt to be around 15 billion years old.
18. Determine three possible scenarios dealing with the future of the universe:
1) The universe will continue to expand forever.
2) The universe will eventually stop expanding and gravity will cause it to collapse.
3) The universe will go through a never-ending cycle of big bangs, expansions, and collapses.
