PASS Scripta Varia 21 - Pontifical Academy of Sciences

GOVIND SWARUP
Figure 2. The sketch indicates evolution of the Universe according to the Big Bang Model. The
Model predicts that weaker radio sources located far away would be much more numerous compared
to those nearby (assuming no evolution of luminosities with cosmic epoch).
method for the purpose. I proposed and directed construction of a cylindrical
radio telescope of a large size, 530m long and 30m wide that was located on
a hill at Ootacamund (Ooty), with its long axis parallel to that of the earth,
taking advantage of India’s location close to earth’s equator. Using the Ooty
Radio Telescope (ORT), we measured angular sizes of ~1000 weak radio
sources with arcsec resolution using the method of lunar occultation. We
found that the weaker sources of smaller flux densities had smaller angular
size, compared to angular size of stronger 3C sources with higher flux densities.
Also, our results indicated cosmic evolution of radio sources, thus providing
independent evidence of the Big Bang Model [20, 21].
80 The Scientific Legacy of the 20 th Century