In the popular imagination, the Big Bang is a great explosion; at one time there was nothing, then matter erupted into previously empty space. However, the Big Bang is the beginning of spacetime itself, not an event in time.

Which is better: to achieve Nirvana, or become a Boddhissatva?

When confronted with a demand that the universe have a cause, infidels have usually pointed out that God was not much of an explanation. This is true enough, but not really a positive argument. After mechanistic explanation became popular, infidels liked to restrict causality to the chain of causes in an eternal material universe, pointing out that no supernatural cause was then necessary. Plausible, but still rather defensive. Today's skeptic can do better. In all likelihood, the universe is uncaused. It is random. It just is.

Attaching a Creator to the boundary is metaphysical skullduggery.

In the popular imagination, the Big Bang is a great explosion; at one time there was nothing, then matter erupted into previously empty space. However, the Big Bang is the beginning of spacetime itself, not an event in time.

Quantum mechanics is so counter-intuitive, physicists have never been able to come up with a comfortable picture of how it works.

Creation out of absolute nothing is a metaphysical quagmire for theists anyway, since nothing must at least have the potentiality for becoming something. Since theists are stuck with potentiality, it might as well be something like a quantum vacuum.