International Space Station (ISS)

The International Space Station (ISS) is the largest orbiting spacecraft ever built. The first residents arrived at ISS in 2000. Only a few of the astronauts have stayed more than six months on board. On the first sight it seems that the space station is floating free from the pull of gravity. People and objects on board the station appear to be weightless. However, gravity pulls on the space station, too. The space station is constantly falling toward Earth's surface, but it also is moving at a very fast speed of five miles per second. It moves at the speed that matches the way Earth's surface curves. An orbiting spacecraft moves at the right speed so the curve of its fall matches the curve of Earth. The spacecraft keeps falling toward the ground but never hits it. It falls around the Earth.

The ISS is a laboratory with an international crew of six people. Crew members spend a lot of time researching many disciplines, for example, space, physical or biological sciences. The solar arrays provide power for the station. They also make the station the second brightest object in the night sky after the moon.

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ISS International Space Station satellites astronaut cosmos