Abstract
The energy conditions give upper bounds on the luminosity distance. We apply these upper bounds to the 192 ESSENCE supernova Ia data to show that the Universe has experienced accelerated expansion. This conclusion is drawn directly from the distance modulus–redshift graph. In addition to being a very simple method, this method is also totally independent of any cosmological model. From the degeneracy of the distance modulus at low redshift, we argue that the choice of w0 for probing the property of dark energy is misleading. One explicit example is used to support this argument.