New study indicates that the Universe could end 'surprisingly soon'

The idea that the Universe will expand forever has been the bedrock of modern cosmology for decades. But new research indicates that the cosmos in which we live may be cyclical and that the growth of spacetime as we know it could be nearing its end.

A study published in the Proceedings of the National Academy of Sciences suggests that dark energy, the mysterious anti-gravitational force that comprises 70 percent of the Universe's mass-energy content, is weakening.

Instead of being a fundamental force of nature burbling up from so-called empty space, dark energy may be a substance called "quintessence," the authors propose, which naturally decays over time.

Theoretical models predict that in the next 65 to 100 million years its influence will wane, leading to a gradual slow-down of cosmic expansion and the eventual collapse of everything.

Paul Steinhardt, the director of Princeton University's Center for Theoretical Science, explained the significance of his team's conclusions.

"Going back in time 65 million years, that's when the Chicxulub asteroid hit the Earth and eliminated the dinosaurs," Steinhardt told Live Science. "On a cosmic scale, 65 million years is remarkably short."

He noted that "the question we're raising in this paper is, 'Does this acceleration have to last forever? And if not, what are the alternatives, and how soon could things change?'"

Steinhardt and his colleagues – fellow Princeton physicist Cosmin Andrei and Professor of Physics Anna Ijjas of the Center for Cosmology and Particle Physics at New York University – came up with two potential futures for the Universe, based on their investigation of quintessence's hypothetical demise.

The implications of both outcomes are enormous.

The first is that spacetime will slowly contract until it becomes so incomprehensibly hot and dense that it triggers another Big Bang. In this scenario, our Universe is only the latest iteration of an infinite cycle of creation and destruction. In other words, believers in reincarnation have much to be excited about.

The second is far less appealing for life but equally as plausible nonetheless – that the decay of quintessence causes a rapid collapse of all of the matter in the Universe in a "Big Crunch." Consequently, no mechanism exists for measuring 'now' millions or billions of light-years away, because the deeper we peer into space, the further into the past we see. That means observers in our region of space would have no idea that the Universe was shrinking until it affects them.

Either way, Steinhardt's paper serves as a reminder that humanity's understanding of the Universe – and our place in it – is constantly evolving.

"Three different theoretical developments point to the same outcome," it concludes. "The end of expansion could occur surprisingly soon."