Re: What is the energy/mass balance of the universe?

This is an interesting question!

The first thing to say is that measurements of the mass density of the universe are tricky, so we don't have precise answers.

The easiest way to answer this question is to consider the density of the various components, i.e., matter and energy, relative to the so-called "critical density" of the universe (which is the density it has to have if the space-time geometry is flat). [Another way of thinking about the critical density is to consider what density is required to make the Universe's expansion stop so that the Universe recollapses in the distant future. If the Universe's density is too large, it collapses; it the Universe's density is too small, it expands forever. The critical density is the density at which the Universe is balanced between these two possibilities.] Current measurements suggest that the density of ordinary matter (electrons, protons and neutrons essentially) only contributes a few percent of the critical density. However, there are many reasons to think that some of the matter in the universe is not of this "ordinary" sort, out of which we are made, but is instead in some exotic form which we have not yet detected. This dark matter could contribute several tens of percent of the criticial density. In other words we suspect that there is more of this dark matter than there is of "ordinary" matter.

By contrast the density of radiation (which is the main energy component) is about 1000 times less, at the present epoch, although in the early universe it actually dominated the matter density. The conclusion would be that most of the energy (apart from the energy of expansion itself) has ended up in material form.

The final twist to this tail is that recent measurements suggest that there exists a strange dark energy pervading the universe, which makes up the remaining proportion of the "critical density" of the universe. This "dark energy" is actually causing the expansion of the universe to accelerate.

So, I don't know if that fully answers your question, but hopefully gets most of the way there!