  We present measurements of the angular cross-correlation between luminous red
galaxies from the Sloan Digital Sky Survey and the cosmic microwave background
temperature maps from the Wilkinson Microwave Anisotropy Probe. We find a
statistically significant achromatic positive correlation between these two
data sets, which is consistent with the expected signal from the late
Integrated Sachs-Wolfe (ISW) effect. We do not detect any anti-correlation on
small angular scales as would be produced from a large Sunyaev-Zel'dovich (SZ)
effect, although we do see evidence for some SZ effect for our highest redshift
samples. Assuming a flat universe, our preliminary detection of the ISW effect
provides independent physical evidence for the existence of dark energy.
