Two possibilities.

(Via Hashem Al-Ghaili)

Scientists are considering whether the mysterious “force” accelerating the universe’s expansion changes with time.

Of late there’s been some scientific ado over a small but notable conflict in measurements of the universe’s expansion rate. The present rate, called the Hubble constant or H0 (pronounced “H-naught”), connects the redshift in an object’s spectra to its physical distance. It also tells us the universe’s age and size, as well as the density required to make the universe geometrically flat.

A long-standing but unproven assumption about the X-ray spectra of black holes in space has been contradicted by hands-on experiments performed at Sandia National Laboratories’ Z machine.

Z, the most energetic laboratory X-ray source on Earth, can duplicate the X-rays surrounding black holes that otherwise can be watched only from a great distance and then theorized about.

“Of course, emission directly from black holes cannot be observed,” said Sandia researcher and lead author Guillaume Loisel, lead author for a paper on the experimental results, published in August in Physical Review Letters. “We see emission from surrounding matter just before it is consumed by the black hole. This surrounding matter is forced into the shape of a disk, called an accretion disk.”

A team of physicists from the UK and Canada have provided a simulation that supports the theory that our universe did not start out the way the Big Bang model proposes, but rather expanded to its current state after a period of contraction—a cycle dictated by the Big Bounce Theory.

The Big Bounce theory states that the universe follows a cycle of contraction and expansion, repeated infinitely. According to this theory, the universe did not begin with a violent explosion, but rather formed as a previous universe expanded or “bounced” back collapsing during the contraction phase of this endless cycle.