Why is it God absolutely necessary?

So many creationists make the claim that something can't come from nothing. Well let me ask you this. How do you know? No one has ever observed nothing. Sure we have seen empty space, but empty space is still existence, therefore empty space is still something. No one has ever observed nothing because nothing only exists outside of the realm of existence. We are part of existence and we do not have the technology to observe or explore the nothingness that may or may not surround our existence. There is no way you can possible know the scientific properties of nothingness or what nothingness is capable of. So how can you possibly know that something can’t come from nothing?