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Astronomers map star movements.
Astronomers use electricity in instruments called transits to help chart star movement. The transit is a precisely-manufactured telescope that has a grid of hair-like wires. The wire grid is illuminated by a tiny electric light so that an astronomer can more scrupulously view the stars' passages in the night sky.

A star's passage into and out of a certain area of the transit's grid is marked by the astronomer who presses a button that electronically activates a mark on a piece of paper. The transit also contains a precise clock that marks the passage of time in seconds with marks on a piece of paper. The two marks are compared and can be said to be accurate within a fraction of a second.

Someone has an eye on you
Man-made satellites are used for communication and for photographing the Earth's surface. Some satellites aid in search and rescue missions; some serve as "spies in the sky" for military purposes.

What powers them and keeps them aloft in their geosynchronous orbits some 22,000 miles above the earth? It's a long way to any gas station! Most of them use the power of solar cells or batteries powered by solar cells. The cells convert the energy of the sun's radiant light into electricity that keeps the satellites functioning

It used to be that when satellites stopped functioning, their orbits were allowed to degrade and they skipped along the Earth's atmosphere until they burned up. Now, scientists can recover satellites, thanks to NASA's space shuttle technology. Satellites can be carried into orbit by the shuttle or can be recaptured and put in its cargo bay for a safe reentry.








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