Alex Filippenko

The Kavli Symposia

 "Evidence from Type Ia Supernovae for an Accelerating Universe and Dark  Energy"

The measured distances of Type Ia supernovae as a function of redshift have shown that the expansion of the Universe is currently accelerating, probably due to the presence of dark energy having a negative pressure.
Moreover, analyses of very distant supernovae reveal an early epoch of deceleration. Several groups have recently measured hundreds of supernovae to determine the equation-of-state parameter of the dark energy. The best-fit value and its first derivative are consistent with the dark energy being Einstein's cosmological constant, or something nearly indistinguishable from it. Any viable theory of quantum gravity will need to be consistent with this result.