| A | B |
|---|
| gravity | a force of attraction or pull between any two objects |
| galaxy | a huge very distant collection of stars |
| inertia | the tendency of a moving object to keep moving in a straight line |
| revolution | one complete trip around the Sun. Earth makes this trip in one year |
| rotation | A complete spin on an axis. Earth makes one of these every day |
| phase | the appearance of the shape of the Moon at a particular time |
| solar eclipse | a blocking of the Sun's light that happens when Earth passes through the Moon's shadow |
| lunar eclipse | a situation that occurs when the Sun, Earth, and Moon are in a straight line and Earth's shadow falls across the Moon |
| tide | the rise and fall of the ocean's surface |
| telescope | an instrument that makes distant objects seem larger and nearer |
| planet | a large object that orbits a star |
| moon | a natural object that orbits a planet |
| satellite | an object in space that circles around another object |
| comet | a mixture of frozen gases, ice, dust, and rock that moves in an elliptical orbit around the Sun |
| asteroid | a rock that revolves around the Sun |
| meteor | a chunk of rock from space that travels through Earth's atmosphere |
| star | an object that produces its own energy, including heat and light |
| nebula | a huge cloud of gases and dust in space that is the first stage of star formation |
| white dwarf | a small and very dense star that shines with a cooler white light. It is the end of a medium-sized star's cycle |
| supernova | a star that has produced more energy than gravity can hold together and explodes |
| black hole | an object that is so dense and has such powerful gravity that nothing can escape from it, not even light |
| constellation | any of the patterns formed by groups of stars in the night sky |
| light-year | the distance that light travels in a year |
| orbit | a path that one object takes around another object |
