Scientists have developed a new model of the universe which suggests its currently observed accelerated expansion could end as early as 100 million years from now, after which it would transition to a phase of contraction.
Researchers, including Paul Steinhardt from Princeton University in New Jersey, say all this may happen “remarkably” quickly, sooner than thought before.
“Going back in time 65 million years, that’s when the Chicxulub asteroid hit the Earth and eliminated the dinosaurs. On a cosmic scale, 65 million years is remarkably short,” Steinhardt told Live Science.
The study, published last month in the journal PNAS, has noted that a form of dark energy (quintessence) could cause the accelerating expansion of the universe to come to an end.
Following this change, they say there would be a smooth transition from expansion to a phase of slow contraction.
Several studies since the 1990s have pointed out that the universe is rapidly expanding with the space between galaxies growing bigger now than it was billions of years ago.
Scientists have theorised that a mysterious force called dark energy is speeding up this observed expansion of the universe.
They say dark energy exerts a negative, repulsive pressure, behaving like the opposite of gravity and causing the rate of expansion of our universe to accelerate over time, rather than to slow down.
Frank Wilczek, a Nobel laureate from the Massachusetts Institute of Technology, has called dark energy “the most mysterious fact in all of physical science, the fact with the greatest potential to rock the foundations.”
While many of the properties of dark energy remain unknown, scientists, including Albert Einstein have theorised that its force was constant, meaning that the universe would expand forever.
In this leading theory, dark energy could be an intrinsic property of space, and the amount of dark energy per unit volume of space could be fixed as a “cosmological constant.”
However, other researchers have suggested that dark energy, if it really exists, may not be a constant and made of something entirely different called the quintessence field.
In this theory, some scientists say the universe may slow and stop expanding, and/or reverse itself.
This may allow the universe to contract until it was smooshed down into a single entity in what is popularly called the “big crunch,” as opposed to the “big bang” which led to the creation of the universe.
Proponents of this theory say dark energy has a dynamic field that they call quintessence – a property that would allow for expansion or contraction of the universe.
Under the theory, the strength of dark energy could potentially weaken, and the antigravitational property of dark energy may eventually go away.
“If dark energy is a quintessence, its push on the expansion could slowly wither or disappear, or could even reverse to become an attractive force, causing the Universe to collapse into a ‘big crunch,” Sean Carroll, a theoretical physicist at the California Institute of Technology in Pasadena, had told Nature in 2020.
In the new study, scientists applied this theory to model how long it might take the universe to slow down, stop, begin contracting, and eventually reach a single point if dark energy is a quintessence.
The model, built using actual data describing features of the known universe, suggests if the idea of quintessence is true, then the universe could already be slowing its accelerated expansion, and could slow all the way to a standstill in approximately 65 million years.
It suggests that after about 14 billion years of the universe expanding since its formation, it may even start a slow phase of contraction “surprisingly soon,” maybe “less than 100 million years from now.”
While this change is not yet detectable, researchers believe the scenario is not far-fetched and fits naturally with recent theories of cyclic cosmology.
However, to validate if the universe is currently contracting, scientists have to rely on signals coming from light-years away which they may not be able to measure for millions of years.