| A | B |
|---|
| QUARTER (HALF) MOON |  |
| GIBBOUS MOON |  |
| CRESCENT MOON |  |
| FULL MOON |  |
| NEW MOON |  |
| EARTH | The only planet that has liquid water, which is necessary to support life. |
| WINTER IN THE NORTHERN HEMISPHERE |  |
| SUMMER IN THE NORTHERN HEMISPHERE |  |
| EARTH'S TILT | This causes the seasons. |
| NIGHT AND DAY | The result of the rotation of the Earth. |
| 24 HOURS | One complete rotation of the Earth takes____.. |
| REVOLUTION | The movement of the Earth around the sun. |
| A YEAR (365 DAYS) | The time it takes the Earth to revolve around the sun. |
| ONE MONTH (27-28 DAYS) | How long it takes the moon to revolve around the Earth. |
| THE MOON | Earth's natural satellite (an object that moves around another) |
| THE MOON'S PHASES | new, crescent, quarter (or half), gibbous, full |
| A STAR | A burning sphere of gases. |
| THE SUN | The closest star to Earth |
| ROCKY INNER PLANET | Mercury, Venus, Earth, Mars |
| GAS GIANTS | Jupiter, Saturn, Uranus, Neptune |
| ASTEROID BELT | Dividing line between inner and outer planets |
| MERCURY | Rocky, dense inner planet. Only inner planet with no atmosphere. Closest to the sun. |
| VENUS | About the same size as Earth. Heavy thick atmosphere that traps heat (surface is 475 degrees C) 2nd from sun. |
| MARS | Scientists believe that liquid water once existed here because photos show valleys and sedimentary rocks. |
| 150 MILLION KM | Earth's distance from the sun. |
| NINE | The number of planets |
| THIRD | Earth is the _____ planet from the sun |
| JUPITER | The largest planet. 3 Earths would fit inside it. |
| SATURN | Planet known for its rings. At least 18 moons. |
| URANUS | A blue-green ball of gas and liquid. The most distant planet visible without a telespcope. |
| NEPTUNE | The farthest away of the Gas Giants |
| PLUTO | The smallest planet. Rocky surface like the inner planets, but probably covered by frozen gases |
| GRAVITY | Force that keeps the planets in motion around the sun |
| PTOLEMY AND ARISTOTLE | They believed that the Earth was the center of the universe |
| COPERNICUS AND GALILEO | They tried to prove that the sun was the center of the universe |
| ASTEROIDS | About 2000 chunks of rock, like tiny planets, orbit around the sun, mostly on a path between Mars and Jupiter. |
| COMETS | Balls of ice and rock, often with tails of gas as they near the sun. |
| METEORS | Chunks of orbiting matter which occasionally hit the Earth's atmosphere, vaporizing and giving off a streak of light. |
| TELESCOPE | Galileo was probably the first person to use this invention to observe the sky |
| SPUTNICK 1 | Modern space exploration began in 1957 with Soviet launch of this satellite |
| SATELLITE | Any natural or artificial body or object that orbits another object |
| PROJECT APOLLO | Landed 12 humans on the moon between 1969 and 1972. |
| VOYAGER SPACE PROBES | Sent back pictures of Jupiter, Saturn, and Neptune |
| SPACE PROBE | A robot vehicle used to explore deep space |
| VIKING 1 AND 2 | Landed on Mars in 1976 and sent back data about the planet's soil and atmosphere |
| PIONEER PROBES | Used instruments to see through the thick clouds that cover Venus |
| MERCURY PROGRAM | Sent the first Americans into space in 1961 |
| HUBBLE SPACE TELESCOPE | Launched in 1990, it produces images five times as sharp as those from any telescope on Earth |
| SPACE SHUTTLES | In use since 1981, the first reusable spacecraft |
| TIDES | The moon's gravity causes these ocean bulges |
