'Not all physicists think time started with the Big Bang - it could have just been a transition from a collapsing to an expanding universe. But now Martin Bojowald of Pennsylvania State University in the US has studied a model of "loop quantum gravity" to show that even if such a pre-Big Bang universe did exist, it would be impossible to grasp certain aspects of it.
'Many think of the Big Bang as the "fireball" that triggered the immensely hot, dense state roughly 14 billion years ago to expand into the vast cosmos we see today. But in classical physics there's a problem: as we extrapolate our models further into the past, they predict the Big Bang as a moment of infinite energy and temperature, called a singularity. Classical models can get to within a hundred-billionths of a second of this singularity, but their equations lose all meaning much before.' (PhysicsWeb article).
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