| A | B |
|---|
| crust | the outermost layer of the Earth |
| AU | 150 million kilometers |
| Kepler's second law of planetary motion | planets travel faster when they are closest to the sun |
| Kepler's third law of planetary motion | a planet's distance from the sun can be calculated if its period of revolution is known |
| core | the center of the sun |
| crust | the layer of the earth on which human beings live |
| rotation | the spinning motion of a planet on its axis |
| revolution | the elliptical motion of a body as it orbits another body in space |
| orbit | the elliptical path a body t akes as it travels around another body in space |
| Kepler's first law of planetary motion | each planet revolves around the sun in an elliptical path |
| chromosphere | the deep red layer of the sun which is visible only during eclipses |
| photosphere | the sun's layer that is visible to people on earth |
| radiative zone | the dense layer of the sun |
| corona | the sun's outer layer |
| mantle | molten layer of the earth |
| AU | the average distance between the earth and the sun |
| core | the layer in the center (middle) of the earth |
| photosphere | the layer of the sun where the gases are thick enough to see; it is the visible surface of the sun |
| corona | the sun's outer atmosphere where the gases are so thin that this layer is visible only during a total solar eclipse |
| chromosphere | the thin, red region of the sun just below the corona which is too faint to see unless there is a total solar eclipse |
| convective zone | the layer of the sun where hot and cooler gases circulate in convection currents |
| AU | astronomical unit |
| radiative zone | it takes millions of years for light energy to travel through this layer of the sun |
| rotation | the cause of night and day on the planet earth |
