Dark energy death
In their study, Steinhardt and his colleagues, Anna Egas of New York University and Cosmin Andre of Princeton University, predict how the properties of matter may change over the next few billion years. To do this, the team created a physical model of the core, showing its repulsive and fascinating powers over time, to match previous observations of the expansion of the universe. Once the team's model could reliably reproduce the history of the expansion of the universe, they expanded their predictions for the future.
"To their surprise, the dark energy in their model can decay over time," Henshaw said. “It can weaken his strength. And if you do it a certain way, the anti-gravity properties of dark energy eventually dissipate and turn back into something that resembles ordinary matter."
According to the team's model, the centrifugal force of dark energy in the midst of its rapid decline could have started billions of years ago. In this scenario, the acceleration of the expansion of the universe is already slowing down today. Soon, perhaps in 65 million years, this acceleration could stop completely then in 100 million years from now, dark energy could become attractive, causing the entire universe to begin to shrink. In other words, after nearly 14 billion years of growth, space could start to shrink.
"It's going to be a very special type of contraction that we call slow contraction," says Steinhardt. “Instead of expanding, space is shrinking very, very slowly.”
At first, the contraction of the universe would be so slow that any hypothetical human still alive wouldn't even notice the changes, Steinhardt said. According to the team's model, it took the universe several billion years of slow contraction to reach half its size today.
The end of the universe?
From there, says Steinhardt, one of two things can happen. Either the universe shrunk until it collapsed on its own in a major "crisis," and spacetime as we know it ended or the universe shrunk enough to return to a state similar to its original state, and another big bang - or "bounce" - occurred. , forming a new universe from the ashes of the old universe. In that second scenario (described by Steinhardt and others in a 2019 paper published in the journal Physics Letter B), the universe follows a periodic pattern of expansion and contraction, rattling and bouncing, constantly collapsing and reshaping. If this is true, our current universe may not be the first or only universe, but rather the latest in an endless chain of universes that expanded and contracted before ours. And it all depends on the changing nature of dark energy.
How much does this all make sense? Henshaw said the new paper's interpretation of the core is a "completely reasonable assumption about what dark energy is."
He added that because all of our observations of cosmic expansion come from objects millions to billions of light years from Earth, current data can only tell scientists about the universe's past, not its present or future. Therefore, the universe may be heading for a crisis, and we won't know until long after the contraction phase begins.
"I guess it just comes down to how convincing you are of the theory and, more importantly, how well can you test it?" Hinshaw's words have been added.
Unfortunately, there's no good way to test whether essence is real, or whether cosmic expansion is starting to slow down, Steinhardt admits. For now, it's just a matter of aligning theory with previous observations and the authors do so skilfully in their new paper. Whether a future of endless growth or rapid decay awaits our universe only time will tell.
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