Definitions

Evaporation: The process by which any substance is converted from a liquid state into, and carried off in, vapor. Puddles on the sidewalk dry up when the sun comes out because the water evaporates.

Erosion: The process by which the surface of the earth is worn away (broken down and carried away) by the action of water, glaciers, winds or waves.

Decomposition: The reduction of formerly living organisms into simpler forms of matter. Your Halloween jack-o-lantern will decompose into mush if you leave it outside until next summer.

Absorption: The process by which one sustance is sucked into another. Place a paper towel over spilled juice and the juice is absorbed into the towel.

Digestion: The process of converting food into chemical substances that can be absorbed and assimilated. The saliva in your mouth and the juices in your intestines break down the food into a form your body can absorb into your cells.

Image credits for this page:
Earth and moon: NASA

Please read: About images and copyright.

M Y P L A C E I N T H E U N I V E R S E

As well as having telescopes on or near the earth, scientists have sent cameras out into space to send back pictures. With these we have been able to see the earth from a distance. Earth looks like a little blue ball of Life in the vast darkness of Space. This picture, taken from the Mars Odyssey spacecraft in 2001, lets us see the true relative size of the earth and its moon, and gives us some idea of how very far away it is from anything else. That helps us to understand that everything on the Earth (except sunlight and meteorites) had to come from the Earth, because it could not have come from anywhere else. Earth is self-sustaining. No delivery ships bring new air or new water or new soil. Through amazing processes like evaporation, precipitation, erosion, decomposition, absorption and digestion, the Earth recycles its molecules to create new things from the molecules that were previously part of something else.