Hawking and Mlodinow (HW), if I understand them, claim the universe can spontaneously arise out of nothing because of a law like gravity. A positive amount of energy is "canceled" by its negative gravitational energy.

That leaves a cluster of questions. But this is interesting: energy is what is conserved via Noether's Theorem to time symmetry. "If a physical experiment has the same outcome at any time, then its laws are symmetric under continuous translations in time; by Noether's theorem, this symmetry accounts for the conservation of energy within this system." (paraphrasing Wikipedia).

Energy, in some sense, is conserved in the HW creation scenario. Therefore, the Lagrangian is invariant with respect to time translations

*t*to*t + deltat*. So the universe could have been created at any time(?)
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