[nimdoc]

I have always thought of space as a potential, not as a cause. That is an interesting thought. I wonder if anyone out there is well enough versed in string theory to comment.

The universe still has to have a source, and appealing to arbitrary necessity by saying that it just happens to exist is not a reasonable or satisfying explanation.

To say the universe just happens to exist is no more or less reasonable or satisfying than saying that a creator just happens to exist. Neither statement is scientific - they are both metaphysical. (One physicist has said that the universe must exist because it is logically impossible for it not to exist. Now, repeat that slowly 3 times, then say it backwards 3 times for good measure.)
I have my doubts that this question can ever be resolved in a “scientific” sense.

To Be, or not to Be, that is the question.

[Physicist]

I have always thought of space as a potential, not as a cause.

I don't know what that means.

The universe still has to have a source

I disagree. "Source" implies causality, which implies time. But time is a property of the universe, and a malleable, manipulable one at that. Time exists in the universe; the universe does not exist in time.

But what you boys are driving at is Heidegger's fundamental question of philosophy: why does anything exist, instead of just nothing? In my opinion, the only meaningful resolution is that of Rand, who declared "Existence exists" to be an axiom.