A model independent measure of the large scale curvature of the Universe
  Cosmological distances as a function of redshift depend on the effective
curvature density via the effect on the geometrical path of photons from large
scale spatial curvature and its effect on the expansion history, H(z).
Cosmological time, however, depends on the expansion history only. Therefore,
by combining distance and lookback time observations (or other estimates of the
expansion history), it is possible to isolate the geometrical curvature
contribution and measure the curvature in a model independent way, i.e., free
from assumptions about the energy content of the universe.
  We investigate two different approaches to accomplish this task; the
differential and the integral approach. The differential approach requires, in
addition to distances, derivatives of distance with respect to redshift as well
as knowledge of the expansion history. The integral approach is based on
measuring the integral of the inverse of the expansion history via measurements
of cosmic time as derived, e.g., from galaxy ages.
  In this paper, we attempt to constrain the large scale curvature of the
Universe using distances obtained from observations of Type Ia supernovae
together with inferred ages of passively evolving galaxies and Hubble parameter
estimates from the large scale clustering of galaxies. Current data are
consistent with zero spatial curvature, although the uncertainty on the
curvature density is of order unity. Future data sets with on the order of
thousands of Type Ia supernovae distances and galaxy ages will allow us to
constrain the curvature density with an uncertainty of less than 0.1 at the 95%
confidence level.
