Contact

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b) Why are astronomers using radio telescopes looking for far stars instead of a telescope?
First of all, what is a radio telescope? The first non-visual spectral region that was used extensively for astronomical observations was the radio frequency band. Telescopes observing at these wavelengths are commonly called radio telescopes. Radio telescopes may be made much larger than optical/infrared telescopes because the wavelengths of radio waves are much longer than wavelengths of optical light. A rule of thumb is that the reflecting surface must not have irregularities larger than about 1/5 the wavelength of light that is being focused. By that criterion a radio telescope is several hundred thousand times easier to figure than an optical telescope of the same size In the movie "Contact," astronomer Ellie Arroway, played by actress Jodie Foster, searches for signs of extraterrestrial life using massive, Earth-bound radio telescopes. Much of Contact's scientific intrigue, based on Carl Sagan's 1985 bestseller, unfolds at two National Science Foundation-supported radio astronomy facilities where real-life astronomical mysteries continue to be probed. Scientists use the government-supported telescopes to detect radio waves not from distant civilizations but from planets, stars, galaxies and other objects in space. Radio observations extend astronomers' reach into space and time, letting them "see" through gas and dust in space to detect celestial objects whose visible light cannot be seen from Earth. In "Contact," Foster hears the first guttural, throbbing message transmitted by other-worldly life using the world's most powerful radio telescope, the Very Large Array in Socorro, New Mexico, a collection of 27 antennas spread in a three-armed configuration across the desert. NSF's National Radio Astronomy Observatory runs the huge dishes, which Foster manipulates in the film from her laptop computer like a high-tech, movable Stonehenge, in reality....
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