Chapter+2+Review

1) Rotation is when the earth spins on its axis. It causes day and night because as the earth rotates only half of it is facing the sun at any time. Revolution is when the earth circles the sun. As the earth is rotating it is also moving around the sun. The difference between rotation and revolution is that rotation is the earth spinning and revolution is the earth circling the sun.   2)  Kepler’s first law of motion states that the planets do not move around the sun in a circle, but in an ellipse. A circle is a perfectly round shape. An ellipse is more like an oval. An ellipse has two points called foci and a circle has only one center point. 3) The solar system consists of the sun, stars, planets, and other bodies that orbit the sun. It is what we live in. The solar nebula is the name of a nebula. The solar nebula is the nebula that formed our solar system.   4)  Planetesimals are what make planets. Another way to think of them is they are baby planets. They are bits of dust that stuck together when they collided inside the solar nebula. They kept getting bigger and bigger until they turned boulder sized. To have a planet, first you must have had a planetesimal. 5) Temperature is a measure of how fast the particles in an object move around. Pressure is the amount of force that is put on something. Pressure was used when our solar system was being made. Pressure and gravity stabilized nebulas. If gas molecules in a nebula move very slowly the temperature is cold, but if they move fast the temperature is high.    6)  The photosphere and corona are both atmospheres of the sun. The corona is the sun’s outer atmosphere. The gases in it are so thin that it is visible is a total solar eclipse. The photosphere is where the gases get thick enough to see. 7) It takes millions of years for light energy to travel to travel through the sun’s **radiative zone**.   8)  **Rotation** of the earth causes night and day. 9) Convection in Earth’s mantle causes **plate tectonics**.   10)  D.   11)  A.   12)  A.   13)  C.   14)  B.   15)  C.   16)  A.   17)  A.   18)  Sometimes the balance in a nebula can be upset. Two nebulas can crash into each other or a nearby star can explode. If a star exploded it would cause material from the star to crash into the cloud. These events compress small regions of the cloud so that gravity overcomes the pressure. This is how the solar nebula began to collapse.
 * __ Astronomy Chapter 2 Review __**