[Prof_Sai]

Dark energy and dark matter are not the names of anything anyone thinks is out there, so much as giving a name to our own lack of understanding. It is sort of like "Planet X" was in the 1930s to 1970s. Dark matter was variously thought to be subatomic particles, or jupiter sized planets floating in deep space, or black holes. Proposals for dark energy are equally varied.

The problem with space nodes is that you wouldn't need to see the edge - you would be able to tell that some parts of space were expanding faster then others. If you weren't in the exact center of a node, there would be obvious asymmetry in the expansion. In fact, the universe looks exceedingly uniform. Also, we have seen back in space/time to the era where the first stars formed, and confirmed that there was nothing else behind that but a dark opaque space as predicted by the big bang.