A space station is a place where people can live and work in space for long periods. It orbits Earth, usually about 200 to 300 miles (300 to 480 kilometers) high. A space station may serve as an observatory, laboratory, factory, workshop, warehouse, and fuel depot. Space stations are much larger than piloted spacecraft, so they provide more comforts. Piloted spacecraft may transport people between Earth and the space station. Unpiloted spacecraft may supply the station with food, water, equipment, and mail.

Small space stations can be built on Earth and launched into orbit by large rockets. Larger stations are assembled in space. Rockets or space shuttles carry modules (sections) of the station into space, where astronauts assemble them. Old modules can be replaced, and new modules can be added to expand the station. A space station has at least one docking port to which a visiting spacecraft can attach itself.

Most docking ports consist of a rimmed doorway called a hatch that can connect with a hatch on the visiting spacecraft to form an airtight seal. When the two hatches open, they form a pressurized tunnel between the station and the visiting spacecraft. The main tasks of a space station crew involve scientific research. For example, they might analyze the effects of microgravity on various materials, investigate Earth's surface, or study the stars and planets.

Astronauts at a space station also devote much of their time to the assembly of equipment and the expansion of the station's facilities. This includes erecting beams, connecting electrical and gas lines, and welding permanent joints between sections of the station. The crew must also fix orreplace broken equipment. ... Full Text

Cosmic Collision

Our home galaxy the Milky Way and Andromeda galaxy are on a collision course! The Andromeda is the most distant object one can see with naked eye. Code named M31 or Messier 31, Andromeda is a giant spiral galaxy of about 300 billion stars. This galaxy is about twice as big as the Milky Way and about 2.5 million light years away from us. The galaxy is moving towards to our own Milky Way at a speed about 500,000 km/hour. Scientists believe ... Full Text

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