Abstract. Observations of supernova explosions halfway back to the Big Bang give plausible evidence that the expansion of the universe has been accelerating since that epoch, approximately 8 billion years ago and suggest that energy associated with the vacuum itself may be responsible for the acceleration.
Abstract. The cosmic triangle is introduced as a way of representing the past, present, and future status of the universe. Our current location within the cosmic triangle is determined by the answers to three questions: How much matter is in the universe? Is the expansion rate slowing down or speeding up? And, is the universe flat? A review of recent observations suggests a universe that is lightweight (matter density about one-third the critical value), is accelerating, and is flat. The acceleration implies the existence of cosmic dark energy that overcomes the gravitational self-attraction of matter and causes the expansion to speed up.
Abstract. Gravitational lenses, besides being interesting in their own right, have been demonstrated to be suitable as ``gravitational standard rulers'' for the measurement of the rate of expansion of the Universe (H0), as well as to constrain the values of the cosmological parameters such as 0 and 0 that control the evolution of the volume of the Universe with cosmic time.
DETERMINATION OF COSMOLOGICAL
PARAMETERS - Wendy L. Freedman (2000)