SALT LAKE CITY — Will it die with a bang or a whimper? Will the universe eventually collapse into a "Big Crunch," a fateful inverse of the "Big Bang"? Or will it expand forever until it leaves a void that is dark, lonely and astonishingly vast?
Those haunting questions stem from one of the great mysteries of science: dark energy. Now, a Utah scientist is part of a team that has thrown a tiny bit more light on the baffling, poorly understood force that seems to permeate the universe.
"Dark energy is something; we don't actually know what the heck it is," said Kyle Dawson, assistant professor in the Department of Physics & Astronomy at the University of Utah.
Since the force was discovered a dozen years ago, scientists have struggled to understand it.
"This one, I would say, in the field of astronomy and cosmology, is the single biggest question," Dawson said.
What is dark energy?
It appears to have a negative pressure, leading to a repulsive effect, and is responsible for the acceleration of the expansion of the universe.
It is thought to account for roughly three-quarters of the energy in the universe.
He and a team of scientists at a half dozen institutions have just published new findings that better define and measure the timetable for dark energy's effect on the expansion of the universe.
In the first split-second after the Big Bang 13.7 billion years ago, there was a brief instant of incredible growth. That moment, known as "inflation," lasted much less than a trillionth of a second.
Almost immediately, the expansion of the universe began slowing down because of the effects of gravity. The universe never actually stopped growing, but the velocity declined substantially over a period of about seven billion years.
As the galaxies drifted further and further apart, though, the gravitational effects were diluted. At that point, roughly halfway through the history of the universe, a new phase of accelerated expansion began. Dark energy kicked in.
For the last seven billion years or so, dark energy has been winning the battle against gravity. The expansion is speeding up, going faster and faster, a finding that rocked the world of science a dozen years ago.
Even Dawson finds it bizarre, and intellectually uncomfortable.
"When you look at the measurements and the observations, it's very hard to argue otherwise," he said. "The universe is very clearly accelerating due to some force that dominates our current universe."
It's a process that has everything to do with the future of the universe as we know it. The bizarre force is causing galaxies, stars, planets, everything in the universe, to fly apart. They are all rushing away from each other at a faster and faster pace.
No one can yet predict with certainty if that process will continue. Perhaps the universe will turn around again. Gravity may win out, pulling the universe into what some scientists have called a "big crunch."
But, according to Dawson, the current data suggests a much darker future. If dark energy keeps pushing faster and faster, it will create a universe of infinite loneliness in which everything is spread out over vast volumes of mostly empty space.
"If I look at galaxies today," Dawson said, "billions of years from now, they will be accelerating so fast that I will no longer be able to see them. I will look out into what's effectively a dark sky."