| alien |
a living being from another planet; extraterrestrial. There is no evidence that aliens exist, but many people believe there is life on other planets. [2/5 definitions] |
| asteroid |
a small, rocky, planet-like body that circles the sun and is mostly found between the orbits of Jupiter and Mars. The size of an asteroid can vary from very tiny to six hundred miles across. |
| climate change |
a major change in Earth's climate that is of current concern and which is associated with an increase in carbon dioxide and certain other gases in Earth's atmosphere. These gases contribute to the increasing temperature of the planet. [1/2 definitions] |
| crust |
the outer layer of Earth, another planet, or a moon. [1/5 definitions] |
| earth |
(often capitalized) the fifth largest planet in our solar system and the third in distance from the sun. [2/4 definitions] |
| earth science |
Earth science is the study of the planet Earth. Earth science is especially interested in what the planet is composed of, its weather, and how the planet developed and continues to change over time. Many different sciences, such as geology and meteorology--the study of weather--are part of earth science. |
| eclipse |
the blocking from view of the sun, a moon, or a planet by another heavenly body. In an eclipse of the sun, the sun is hidden from earth's view by the moon passing between the sun and the earth. [1/3 definitions] |
| extraterrestrial |
existing or coming from a place outside planet Earth. |
| galaxy |
a collection of billions of stars and other matter held together by gravity. Our planet Earth and the sun belong to the Milky Way galaxy. They are only tiny parts of this galaxy. |
| geology |
the land forms and rocks of a particular place on the earth or other planet. [1/2 definitions] |
| globe |
the world; planet Earth. [1/2 definitions] |
| Jupiter |
the largest planet in the solar system and fifth in distance from the sun. Jupiter has sixteen moons and is more than one thousand times larger than Earth. [1/2 definitions] |
| mantle |
the layer of the earth that lies between the crust and the core. The crust is the top layer of the earth--the layer we live on. The core is the center of our earth. The mantle is very thick and makes up most of the entire planet. [1/2 definitions] |
| Mars |
the seventh largest planet in the solar system and fourth in distance from the sun. Mars is known as "the red planet" because of its unusual color. [1/2 definitions] |
| mercury |
(capitalized) the planet of the solar system that is nearest to the sun. Mercury is the second smallest planet. [1/3 definitions] |
| Neptune |
the fourth largest planet in the solar system and eighth in distance from the sun. [1/2 definitions] |
| orbit |
the curved path in which a planet, satellite, or spacecraft moves in a circle around another body. [1/3 definitions] |
| plate |
a tectonic plate, one of the parts of the outer layer of planet Earth. Tectonic plates cover the whole planet and make up both the land that humans and animals live on and the land under the oceans. Tectonic plates move very, very slowly and they touch each other as they move. Sometimes this contact between the tectonic plates causes things like volcanoes, earthquakes, and the building up of mountains. [1/7 definitions] |
| Pluto |
a dwarf planet in the Earth's solar system, formerly considered a planet and the one that was smallest and farthest from the sun. [1/2 definitions] |
| satellite |
a heavenly body that moves around a planet or another larger body. [2/3 definitions] |
| Saturn |
the second largest planet in the solar system and sixth in distance from the sun. Saturn is known for the icy rings that circle its middle. [1/2 definitions] |