  The 2011 Nobel prize in physics has been awarded to S. Perlmutter, A. Riess
and B. Schmidt for their path breaking discovery that the rate of expansion of
the universe is increasing with time. The trio used Type Ia supernovae (SNe Ia)
as standard candles to estimate their luminosity-distances. To appreciate some
of the far reaching implications of their work, I have provided an elementary
exposition of general theory of relativity, accelerated expansion of the
universe, luminosity-distance, SNe Ia and the cosmological constant problem.
