The whirring sound stirs me out of my reverie. Amidst the swishing of leaves in the wind, the new sound rattles you. But the sight accompanying it is magnificent. It is what I have come here for. Tilting my head upwards, I behold the sky through a net of wire. A huge antenna dish (like the antenna that the cable-operator has on his roof) is moving atop a stationary structure. It is not a mean task for a 45 metre antenna to move mechanically. It is awesome. It is beautiful. Stretching my eyes over the horizon, I see few more antennae – all tilting together searching for a common goal. Located amidst the lush greenery, on the quiet and isolated outskirts of Pune, is Khodad (near Narayangaon) where I’m standing.
What I’m watching is the Giant Metrewave Radio Telescope (GMRT) of the Tata Institute of Fundamental Research, the world’s largest radio telescope. It consists of thirty 45-m dishes arranged in a Y-shaped configuration spread over distances of ~25 km. Work on GMRT was started ~ 1989 under the leadership of Prof. Govind Swarup and by 1995, all the 30 antennas were operational. The telescope is being used by astronomers from all over the world to study and learn more about astronomical objects emitting in radio frequencies. GMRT works in the radio regime where the wavelength is of the light is order of a metre (the wavelength of the red light that you see is about a million times smaller than a metre).
There are many astronomical objects which emit mainly in the radio wavelengths but only the powerful emitters can be detected since these objects are very distant. One of the science projects of GMRT is to detect hydrogen from very distant galaxies. Hydrogen forms a major constituent of our Universe from which galaxies formed. Atomic hydrogen emits radio emission at 21 cm. It is believed that the Universe is expanding and the distant galaxies are moving away further from us. The wavelength of light from objects moving away from us shifts to longer wavelengths (called red-shifting; this phenomenon is called Doppler effect). GMRT would enable us to detect the radio emission from hydrogen in these distant galaxies. Another set of objects that emit radio pulses is the pulsars. These are rapidly rotating objects with very high densities (20 million tonnes per cubic cm!). Besides, the radio emission from ionised hydrogen close to newly formed stars as well as from supernova remnants (explosions accompanying death of massive stars) are also being studied using GMRT.
While practical sciences are calling the shots today, it is refreshing to see India investing in fundamental sciences. GMRT was a huge project, and a lot of research went into it. Interestingly, the wired net used to make the antenna-dishes is an innovative technology by the Indian engineers. GMRT is one of the most challenging experimental programmes in basic sciences undertaken by Indian scientists and engineers.
The antennas have stopped moving and started collecting radio waves from the source. And as I retrace my steps back towards the Observatory building, I can feel the pride in my strides.
P.S: For more information on GMRT, goto http://www.gmrt.ncra.tifr.res.in/
