Buffalo NY (SPX) Aug 11, 2022 In trying to understand the nature of the cosmos, some theorists...
In trying to understand the nature of the cosmos, some theorists propose that the universe expands and contracts in endless cycles.
Because this behavior is hypothesized to be perpetual, the universe should have no beginning and no end - only eternal cycles of growing and shrinking that extend forever into the future, and forever into the past.
Cyclic universes described under this model must have a beginning, Kinney and Stein conclude.
"People proposed bouncing universes to make the universe infinite into the past, but what we show is that one of the newest types of these models doesn't work," says Kinney, PhD, professor of physics in the UB College of Arts and Sciences.
If the universe had a beginning, how did it begin? Kinney is author of a 2022 book titled, "An Infinity of Worlds," which tells the epic story of cosmic inflation, a competing theory about the origins of the universe.
A truly cyclic universe would circumvent these problems: If the universe is engaged in endless cycles of expansion and contraction, it need not have a beginning at all.
"Unfortunately, it's been known for almost 100 years that these cyclic models don't work because disorder, or entropy, builds up in the universe over time, so each cycle is different from the last one. It's not truly cyclic," Kinney says.
"A recent cyclic model gets around this entropy build-up problem by proposing that the universe expands a whole bunch with each cycle, diluting the entropy. You stretch everything out to get rid of cosmic structures such as black holes, which returns the universe to its original homogenous state before another bounce begins."
Of course, there are further research questions, Kinney says: "Our proof does not apply to a cyclic model proposed by Roger Penrose, in which the universe expands infinitely in each cycle. We're working on that one."
An international team of 23 researchers led by Maria Dainotti, Assistant Professor at the National Astronomical Observatory of Japan, has analyzed archive data for powerful cosmic explosions from the deaths of stars and found a new way to measure distances in the distant Universe.