I ran a search and didn't see anything posted recently, at least, on the current thoughts behind the zero-energy universe idea. http://en.wikipedia.org/wiki/Zero-energy_universe I had a few questions about this: 1) What is the opinion of people on this site of the validity of this idea in general? 2) The positive energy in the form of matter is supposed to be exactly or nearly exactly canceled out by the negative potential energy in the form of gravity. What about electrical potential energy though, doesn't this also factor in? If not, why? And 3) I read somewhere that observationally, the 3-d metric of space is found to be very close to flat, which supports the zero-energy model, but the 4-d metric is supposed to be curved. Is this true? Does this refer to perhaps a negative curvature of Minkowski spacetime? How does that play into the zero-energy universe model and, also, how is dark energy supposed to fit in?