Cosmological Problems

Abstract

One of the most important problems concerning the very early Universe is the “horizon problem”. According to the standard Big Bang theory, the “radius of the Universe” (that is the scale factor R) during the early Universe was increasing with time as

$$ R\,\infty \,{t^{{1/2}}} $$

((11.1))

, where t is the age of the Universe. This implies that the expansion is fastest when t → 0 when, in fact, the derivative of R tends to infinity. That is, the beginning of the expansion is an enormous explosion with infinite velocity.