  The SN1a data, although inconclusive, when combined with other observations
makes a strong case that our universe is presently dominated by dark energy. We
investigate the possibility that large distance modifications of the curvature
of the universe would perhaps offer an alternative explanation of the
observation. Our calculations indicate that a universe made up of no dark
energy but instead, with a modified curvature at large scales, is not
scale-invariant, therefore quite likely it is ruled out by the CMB
observations. The sensitivity of the CMB spectrum is checked for the whole
range of mode modifications of large or short distance physics. The spectrum is
robust against modifications of short-distance physics and the UV cutoff when:
the initial state is the adiabatic vacuum, and the inflationary background
space is de Sitter.
