  We present new weak lensing observations of 1E0657-558 (z=0.296), a unique
cluster merger, that enable a direct detection of dark matter, independent of
assumptions regarding the nature of the gravitational force law. Due to the
collision of two clusters, the dissipationless stellar component and the
fluid-like X-ray emitting plasma are spatially segregated. By using both
wide-field ground based images and HST/ACS images of the cluster cores, we
create gravitational lensing maps which show that the gravitational potential
does not trace the plasma distribution, the dominant baryonic mass component,
but rather approximately traces the distribution of galaxies. An 8-sigma
significance spatial offset of the center of the total mass from the center of
the baryonic mass peaks cannot be explained with an alteration of the
gravitational force law, and thus proves that the majority of the matter in the
system is unseen.
