In general relativity the equation t1 = t2 ( 1 - 2 GM/ r c ^ 2) ^1/2 is often mentioned. If the mass, M, is equal to the mass of the universe - 10 ^ 52 kg - then r cannot be less than 10 ^ 24 metres without invoking the idea that a time can be imaginary. But could an equally valid interpretation be that the universe started out no smaller than 10 ^ 24 metres? The temperature of the universe one second after the Big Bang is thought to be 10 ^10 K, and if the temperature of the cosmic microwave background nowadays, is extrapolated back from 10^26 metres to 10 ^ 24 metres, this would give about this temperature [( 10^26 )^4 / (10^24)^4 x 1000 = 10^11 K ( the term of 1000 allows for redshift of cmbr photons). The above scenario would mean that general relativity does not break down at the time of the big bang and so quantum gravity might not be needed to explain the Big Bang.