Geocentric describes the idea that everything revolved around Earth, compared to modern knowledge that everything revolves around the Sun (our star).
2) Briefly describe the major levels of structure (such as planet, star, galaxy) in the universe.
Planet: (a) Orbits a star, (b) large enough for its own gravity to make it round, (c) has cleared most other objects from its orbital path. Sun: The star of our solar system.
Star: Large, glowing ball of ignited gas that generates heat and light through nuclear fusion in its core. Galaxy: A great island of stars in space, containing a few hundred million or trillion stars held together by gravity, orbiting a common center.
3) What do we mean when we say that the universe is expanding? How does expansion lead to the idea of the Big Bang?
Observations of distant galaxies show that the universe is expanding by an average distance increase between galaxies. We are able to trace back at this rate to determine what we were all one universe and where the Big Bang might have started.
4) What did Carl Sagan mean when he said that we are "star stuff"?
Star stuff refers to the knowledge that all the elements in the universe are created from stars, including ourselves. The bigger the star, the heavier the elements.
5) How fast does light travel? What is a light-year?
Light travels at a speed of 300,000 km/sec. From moon to Earth, it takes about 1 second for light to travel. From the sun to the Earth is takes about 8 minutes. On light-year's travel = 10 trillion km (6 trillion miles).
6) Explain the statement: The farther away we look in distance, the farther back we look in time. Because light takes so long to travel these long distances, the lights we are seeing are actually trillions of years old.
7) What do we mean by the observable universe? Is it the same thing as the entire...