7.2. Ten Years Ahead?
If we were to reconvene 10 years from now, what would be the ``hot topics'' on the agenda? The key numbers specifying our universe - its geometry, fluctuations and content - may by then have been pinned down. I've heard people claim that cosmology will thereafter be less interesting - that the most important issues will be settled, leaving only the secondary drudgery of clearing up some details. I'd like to spend a moment trying to counter that view.
It may turn out, of course, that the new data don't fit at all into the parameter-space that these numbers are derived from. (I was tempted to describe this view as ``pessimistic'' but of course some people may prefer to live in a more complicated and challenging universe!). But maybe everything will fit the framework, and we will pin down the contributions to from baryons, CDM, and the vacuum, along with the amplitude and tilt of the fluctuations, and so forth. If that happens, it will signal a great triumph for cosmology - we will know the ``measure of our universe'' just as, over the last few centuries, we've learnt the size and shape of our Earth and Sun.
Our focus will then be redirected towards new challenges, as great as the earlier ones. But the character and ``sociology'' of our subject will change: it will bifurcate into two sub-disciplines. This bifurcation would be analogous to what actually happened in the field of general relativity 20-30 years ago. The ``heroic age'' of general relativity - leading to the rigorous understanding of gravitational waves, black holes, and singularities - occurred the 1960s and early 1970s. Thereafter, the number of active researchers in ``classical'' relativity declined (except maybe in computational aspects of the subject): most of the leading researchers shifted either towards astrophysically-motivated problems, or towards quantum gravity and ``fundamental'' physics.
What will be the foci of the two divergent branches of ``post classical'' cosmology we'll be pursuing a decade from now? One will be ``environmental cosmology'' - understanding the evolution of structure, stars and galaxies. The other will focus on the fundamental physics of the ultra-early universe (pre-inflation, m-branes, multiverses, etc). A few words about each of these: