"Quantum events have a way of just happening, without any cause, as when a radioactive atom decays at a random time. Even the quantum vacuum is not an inert void, but is boiling with quantum fluctuations. In our macroscopic world, we are used to energy conservation, but in the quantum realm this holds only on average. Energy fluctuations out of nothing create short-lived particle-antiparticle pairs, which is why the vacuum is not emptiness but a sea of transient particles. An uncaused beginning, even out of nothing, for spacetime is no great leap of the imagination."