Is the rate at which the universe expanding slowing down, speeding up, or remaining constant?

Citing hyperphysics, they note that "since the 1990s it has become apparent that type Ia supernovae offer a unique opportunity for the consistent measurement of distance out to perhaps 1000 Mpc." Dark energy is to blame.

A 1997 study of supernovas found that the rate of expansion of the universe is increasing.

The Hypothesis was that the rate of expansion should be decreasing. This Hypothesis was based on the theories that the material universe we observe is eternal and would recycle between a period of expansion such as the big bang and a period of contraction such as a big crush reforming for another big bang.

The empirical evidence contradicted the Hypothesis of a decreasing rate of expansion. This brings into question the theory that the material universe we see is eternal. From the evidence it is certain that the present universe will not recycle and will experience a heat death in the future.

Presently scientists are still grappling with the implications of an expanding, non eternal universe. No agreement has been reached as to theories that will replace the old theories of an eternal material universe that recycles. Perhaps the naturalistic world view itself needs to be replaced.

A phenomenon called dark energy is responsible for the universe's current acceleration of expansion.