Beginning early in the 20th century with the discovery that the spiral nebulae were giant systems like our own Galaxy and the Hubble/Slipher finding that the velocity difference between pairs of galaxies increased roughly linearly with their separations, the stage was set for our modern cosmological models framed as solutions to Einstein's equations for perturbations growing gravitationally in an approximately uniform and isotropic cosmos.

The startling discovery, which was very slow to be accepted, that most of the gravitating matter in the universe is "dark" and of (still) unknown composition and the still more puzzling but now widely accepted conclusion that gravity on the largest scales is overwhelmed by a repulsive force associated with "dark energy" completes the well established, if somewhat bizarre, standard model. Within this framework, very small amplitude, approximately scale-invariant, adiabatic perturbations were imposed by still unknown processes. All current large scale cosmological observations are consistent with this picture, and the detailed computer simulations based on the model appear to fit with steadily increasing precision both the detailed knowledge that we have of the local universe and the increasingly accurate evolutionary picture that we can construct by studying our own past light cone with large ground and space based telescopes that effectively use the universe as a time machine. Hoping to fill the substantial gaps in our understanding, major experiments are underway which should better constrain the unknown parameters and perhaps can test more sharply the present dominant paradigm.

 

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For more information, contact:

Adil Hassam
hassam@umd.edu
301-405- 1417

Arthur LaPorta
alaporta@umd.edu
301-405-3291