After a brief general introduction to Radio Astronomy and its uniqueness in probing the Universe, I will describe some of the great discoveries that have been made by radio astronomers, such as Radio Galaxies, Quasars that have indicated presence of massive Black Holes at their centre, discovery of the Cosmic Microwave Background Radiation that provides strong support to the Big Bang Model.
I will then describe the principles of a radio telescope and of the Giant Metrewave Radio Telescope (GMRT) that has been built by NCRA-TIFR 80 km north of Pune. The GMRT is the largest radio telescope in the world operating in the band of about 130 MHz to 1430 MHz. Finally, I will discuss briefly proposed exploration of the Moon by observing its thermal radio emission using the GMRT.