A half century ago we had a largely conjectural picture of the large-scale structure of the physical universe, of its material contents, and of the main process that drive transformations among the states of matter and radiation. Now our world picture has a substantial basis in experiments and observations and the attendant theories. This has been an evolutionary process: none the entries in the inventory in Table 1 requires a substantial departure from ideas that are under discussion, and in many cases have been in the literature for decades. The important new development is that we now have observational support for the many entries in Table 1, and a network of tests that demonstrate that a considerable part of the inventory is a believable approximation. Continued advances in the observational and theoretical basis for the inventory surely will yield unexpected revisions and additions; we are attempting to draw large conclusions from limited observations of an exceedingly complex universe. However, the big surprise at the moment is that it is now possible to find an inventory with observational support for the largest ~ 40 forms of energy.
We have benefited by advice from Dave Arnett, John Bahcall, Michael Blanton, Pierre Bergeron, Bruce Draine, Doug Finkbeiner, Peter Goldreich, David Hogg, Guinevere Kauffmann, Julian Krolik, Jim Liebert, Geoff Marcy, Bruce Partridge, Martin Rees, Neill Reid, Aldo Serenelli, Mike Shull, Paul Steinhardt, Tomonori Totani and Simon White.
PJEP thanks the Japan Society for Promotion of Science for supporting his visit to Japan, where this work was initiated. MF received support for this work from the Monell Foundation at the Princeton Institute for Advanced Study, and a Grant in Aid from the Japanese Ministry of Education at the University of Tokyo.