Nothing is the absence of anything, that is, non-existence. Nothing is not the same as the empty set, which exists as the set that mathematically denotes nothing, nor is it the same as zero, which exists as the number that denotes how many members the empty set contains. In physics, nothing is not a vacuum, because a vacuum not only contains energy but exists in space and time; nor is it a singularity, which contains a greatly deal of concentrated matter and energy. So, can there be nothing? No. "To be" implies existence of some sort: the one thing we can be absolutely sure has never existed or will exist is nothing.