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. Electronically linked to simulate a single radio telescope up to 20 miles in diameter, the antennas can be bunched together or moved apart along railroad tracks into different configurations. About 700 astronomers visit the VLA each year to observe the universe.
In "Contact," Foster gets her scientific start at another NSF-supported facility, the Arecibo Observatory, a huge, stationary radio dish operated by Cornell University in the lush mountain setting of Puerto Rico. The 1000-foot reflector dish, also featured in the James Bond film, "Goldeneye," is the largest stationary radio telescope and most powerful radar in the world. Russell Hulse and Joseph Taylor of Princeton University earned a Nobel Prize by using the dish in the 1970s to discover the first pulsar in a binary system, confirming a prediction of Einstein's theory of general relativity.
In the early 1990s, Arecibo was used to detect the first planets outside...