While the Big Bang model is well established in cosmology, it is likely to be refined in the future. Little is known about the earliest moments of the universe's history. <answer>The Penrose–Hawking singularity theorems</answer> require the existence of a singularity at the beginning of cosmic time. However, these theorems assume that general relativity is correct, but general relativity must break down before the universe reaches the Planck temperature, and a correct treatment of quantum gravity may avoid the singularity.
Which theorems require the existence of a singularity at the beginning of time?
The Penrose–Hawking singularity theorems