As mentioned above, the universe is the experiment of last resort for particle physicists who can no longer command the political will to build larger particle accelerators (the last U.S. project was mothballed when projections ran to $20 billion). Cosmology is a rapidly evolving field, and astrophysicists are constantly fielding instruments that improve the breadth and detail of our observations of the universe.
From this, it would seem that any inferences for particle theory might be subject to frequent revision. In fact, the history of dark matter exhibits just this kind of instability. Every year, there seem to be new and progressively more contradictory constraints on its properties.
Therefore, the list below can only be considered a sketch of this complex and rapidly developing field. It consists of those results crude enough to have survived the observational revolutions of the last 25 years. The epithet (crude) should be taken as a characterization of my currency in this area: much more sensitive measurements are being obtained by improved satellite- and ground-based observatories. I am not an expert in these areas.
- We observe no galactic-scale defects in the vacuum distribution of the gauge fields. Theoretically, the 10 spatial dimensions of super-string theory are necessary to suppress topological defects in the gauge fields that would give rise to galactic-scale structures.
- The universe evolved as a cool bubble in a soup of particles and fields originally heated beyond the Planck Scale. Beyond this energy, particles readily can pierce the resistance to motion along the seven spatial dimensions that have collapsed in our era.
- The universe is gravitationally closed. Specifically, the expansion of the universe, at very early times, is determined by the release of energy from fields that are converted to mass precisely sufficient to stop the expansion.
- The most directly evident consequence of the expansionary epochs of the Big Bang is the Hubble expansion. Light originating from distant cosmological objects is "red-shifted" in a manner consistent with the predictions of relativity theory for rapidly moving objects. That we appear to be in the center of the expanding field is readily understood from the predicted homogeneity of the expansion.
- Black-body residue (microwave background radiation) is consistent with a phase transition that occurred when the charged particles (electrons and protons) combined to form atoms, and the expected growth in the size of the universe since that epoch.