Ask the Astronomer
Astronomer William Georgevich replies:
Your question is an excellent one because cosmologists have been posing it for decades. The best answer comes from Stephen Hawking who said you cannot ask what happened before the Big Bang. Time and Space BEGAN with the Big Bang, therefore there was no before.
Regarding the part of your question about nothingness, If time and space began with the Big Bang then there was no space or nothingness either.