Science deals with testable hypotheses, i.e. ideas that are falsifiable through prediction and experiment. As it is only possible to interact with the contents of the Universe, it is essentially impossible to ask a scientific question about what is external to the Universe, whether spatially or temporally (assuming either is even possible).
It is possible that if there are additional dimensions and mutliple universes that interact with the 4 traditional dimensions, then we may eventually be able to learn of things that were once external to the Universe. However, such ideas are currently not testable and so might be classified as applied mathematics rather than science.
In short, questions about events that were before or outside the Universe are not currently scientific questions, and likely never will be.
This page was last updated on July 3, 2015.