The signal is then sent through a cable to your house. Cellular phones also use radio waves to transmit information. These waves are much smaller that TV and FM radio waves. Objects in space, such as planets and comets, giant clouds of gas and dust, and stars and galaxies, emit light at many different wavelengths. These long waves are in the radio region of the electromagnetic spectrum.
Radio telescopes are dishes made out of conducting metal that reflect radio waves to a focus point.
Because the wavelengths of radio light are so large, a radio telescope must be physically larger than an optical telescope to be able to make images of comparable clarity. Together, the dishes can act as one large telescope whose size equals the total area occupied by the array. The structure of those interference patterns, and how they change with time as the earth rotates, reflect the structure of radio sources in the sky. Many astronomical objects emit radio waves, but that fact wasn't discovered until 1932. Since then, astronomers have developed sophisticated systems that allow them to make pictures from the radio waves emitted by astronomical objects.