  $\gamma$-ray bursts have baffled theorists ever since their accidental
discovery at the sixties. We suggest that these bursts originate in merger of
neutron star binaries, taking place at cosmological distances. These mergers
release $\approx 10^{54}ergs$, in what are possibly the strongest explosions in
the Universe. If even a small fraction of this energy is channeled to an
electromagnetic signal it will be detected as a grbs. We examine the virtues
and limitations of this model and compare it with the recent Compton \g-ray
observatory results. We also discuss the potential application of grbs to study
cosmology and show that these burst might lead to a new and independent
determination of both $H_0$ and $\Omega$.
