By Vidya Rajan, Columnist, The Times The story so far: The hot, dense singularity that was the source of the Big Bang exploded about 13.8 billion years ago (bya) and the energy in the explosion spread, cooled and became lumpy. The lumps were matter (~5%), dark matter (~25%), and dark energy (~70%). To break it up into timelines after the instant of the Big Bang (A.B.B.):