A new theory explains the accelerating universe without invoking mysterious, unseen dark energy to account for the expansion. But it also gets rid of singularities, an unchanging speed of light...and the most famous astrophysical phenomenon of all, the Big Bang.
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The observation of certain supernovas in the late 1990s led astronomers to the very unexpected discovery that the universe is expanding, and that the expansion is speeding up. There was nothing in the existing laws of physics to account for this, and so the only solution was dark energy - a mysterious force so named because we've never detected it, and yet it has to make up 75% of all the energy and mass in the universe for it to account for this cosmic acceleration. Also, the existence of dark energy weakens the supposedly inviolate law of conservation of energy, if not negates it completely. Cosmologically speaking, that's a problem.
And yet, clumsy and unlikely as that all sounds, it's the best explanation we've got for our observations of the universe...until now. Wun-Yi Shu, a physicist at Taiwan's National Tsing Hua University, has come up with a bold new cosmological framework that solves the dark energy problem. At its most basic, the theory states that the universe has three basic dimensions - mass, time, and length - and these three properties can be converted between each other. He then proposes two new constants, κ and τ, as the conversion factors between time and length and mass and length respectively.
So what does that all have to do with cosmic expansion? Shu's theory holds that, as the universe expands, mass and time get converted to length and space, and then this conversion happens in reverse when the universe enters a period of contraction. The universe then becomes a neverending cycle of expansion and contraction, an eternal cosmos without beginning or end. So bye-bye dark energy...but bye-bye Big Bang as well. On the plus side, we do get the conservation of energy back.
Still, the Big Bang isn't the only singularity removed from existence in this scenario - all the singularities thought to be at the centers of black holes have to go as well. And maybe the craziest part is that his two new constants, κ and τ, mean that Einstein's old constants, c and G, are now free to change over time. Considering c is the speed of light and G is the gravitational constant, the fact that they might vary - even if it's only in minute amounts over billions of years - is a very big deal, and maybe the most exciting part of this new theory.
Shu points out that his theory has already produced good results, as it explains better than any other cosmological framework the supernova data that started this whole mess over a decade ago. That said, he does face one major stumbling block - his theory can't yet explain the cosmic microwave background, the faint radiation that permeates the universe and is thought to be left over from the Big Bang. As such the race is on - either Shu can account for the background radiation, the cosmology community can find hard evidence of dark energy, or a third, perhaps even weirder theory is just waiting to be formulated that will knit all the mysteries together.