text: For a flat universe, this quantity results in a late contribution to the integrated Sachs-Wolfe effect.
full_question: For a flat universe, this quantity results in a late contribution to the integrated Sachs-Wolfe effect. Evidence for this quantity was provided by type Ia (one a) supernova with redshifts less than one that were fainter than expected while those at redshifts greater than one were brighter than expected. The value of this quantity predicted by quantum field theory is an unimaginable 120 orders of magnitude larger than the observed value. The standard model of cosmology is named for this quantity and cold dark matter. It was proposed as a fudge factor to allow a static solution for the equations of general relativity. It's the homogeneous energy density of space causing the acceleration of the universe's expansion, making it the best candidate for dark energy. For 10 points, name this quantity symbolized lambda that Albert Einstein called his "greatest blunder".
first_sentence: For a flat universe, this quantity results in a late contribution to the integrated Sachs-Wolfe effect.
raw_answer: cosmological constant [or lambda until it is read; or dark energy or vacuum energy until "homogeneous energy" is read]