Satellites

A satellite is an object in space that orbits or circles around a bigger object. There are two kinds of satellites: natural (such as the moon orbiting the Earth) or artificial (such as the International Space Station orbiting the Earth).

There are dozens upon dozens of natural satellites in the solar system, with almost every planet having at least one moon. Saturn, for example, has at least 53 natural satellites, and one artificial one — the Cassini spacecraft, which is exploring the ringed planet and its moons.

Artificial satellites, however, did not become a reality until the mid-20th century. The first artificial satellite was Sputnik, a Russian beach-ball-size space probe that lifted off on Oct. 4, 1957. That act shocked much of the western world, as it was believed the Soviets did not have the capability to send satellites into space.

In October 1957, the Soviets finally proved Newton correct when they launched Sputnik 1 -- the first artificial satellite to orbit Earth. This kick-started the space race and initiated a long-term love affair with objects designed to travel in circular paths around our planet or other planets in the solar system. Since Sputnik, several nations, led predominantly by the United States, Russia and China, have sent some 2,500 satellites into space [source: National Geographic]. Some of these man-made objects, such as the International Space Station, are massive. Others might fit comfortably in your kitchen breadbox. We see and recognize their use in weather reports, television transmission by DIRECTV and DISH Network, and everyday telephone calls. Even those that escape our notice have become indispensable tools for the military.