In an article called "From big bang to big bounce" published in New Scientist in 2008, author Anil Ananthaswamy outlines two different theories that lead to our universe being cyclic. 1: "Cosmologists are still very much in the dark about dark energy. Some theoretical models speculate that the nature of dark energy could change over time, switching from a repulsive to an attractive force that behaves much like gravity. If that happens, the universe will stop expanding and the galaxies will begin to rush together." 2: "A question mark also hangs over the universe’s matter and energy density, which we have not measured with sufficient accuracy to be sure that the universe will not eventually stop expanding. If it turns out to be a smidgen greater than current observations, then it is a recipe for cosmic collapse." He goes on to say that both theories describe a universe which expands and contracts indefinitely - a cyclic universe (or what Carl Sagan referred to as an oscillating universe in his Cosmos series). Have we made progress on these two theories since 2008? Have they been thrown out? Is there, in your opinion, better contenders when it comes to describing a cyclic universe, or should the idea be abandoned altogether? Input much appreciated.