It comes down to predictive power: in the set of maps between measured inputs and observed outputs, how much "data compression" does your theory do on that set? This is greatly complicated in areas like cosmology w/o laboratory experiments to control and maximize your measured inputs.
So, the Lambda-CDM (dark energy + dark matter) model does well I think, esp. since we probably understand the young universe better than our present one through collider experiments. Certainly, all the scientists I interact with have an open mind for alternate cosmologies, and some even for modified gravity (though the recent "precision" gravity tests all align with minimal Einsteinian gravity). Dark matter is also attractive because we think that stable, gravitational-only particles are quite plausible at around 1 TeV. Finally, WMAP strongly confirms the canonical picture of rapid, dilute, homogeneous expansion at the time of the radiation decoupling (though perhaps not necessarily the present).
Of course, the apparent necessity of dark energy confuses everyone. Really, the only theoretical motivation for it is that Einstein's equation allows it :)
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So, the Lambda-CDM (dark energy + dark matter) model does well I think, esp. since we probably understand the young universe better than our present one through collider experiments. Certainly, all the scientists I interact with have an open mind for alternate cosmologies, and some even for modified gravity (though the recent "precision" gravity tests all align with minimal Einsteinian gravity). Dark matter is also attractive because we think that stable, gravitational-only particles are quite plausible at around 1 TeV. Finally, WMAP strongly confirms the canonical picture of rapid, dilute, homogeneous expansion at the time of the radiation decoupling (though perhaps not necessarily the present).
Of course, the apparent necessity of dark energy confuses everyone. Really, the only theoretical motivation for it is that Einstein's equation allows it :)