In a novel study, a trio of scientists explores the enigmatic concept of dark energy, the unseen force seemingly driving the universe's expansion at an accelerated rate. The team's model presents dark energy as an evolving entity, dubbed quintessence, with the potential to degrade over time.
The investigation demonstrates that the universe's expansion, which has been on an acceleration path for billions of years due to dark energy's repulsive force, might be losing its strength. The team's model predicts an abrupt end to the universe's acceleration within the forthcoming 65 million years. Following this, the universe could cease its expansion entirely within the next 100 million years, transitioning into a period of slow contraction, potentially culminating in the demise or potential rebirth of time and space[4].
This entire process could occur relatively swiftly, mentions Paul Steinhardt, study co-author and director of the Princeton Center for Theoretical Science at Princeton University in New Jersey.
Gary Hinshaw, a physics and astronomy professor at the University of British Columbia not affiliated with the study, asserts that this theory is neither controversial nor implausible, but it is currently unverifiable due to its reliance on past observations of expansion and the unresolved nature of dark energy.
The concept of dark energy surfaced in the 1990s when scientists discovered the universe's accelerated expansion. This invisible entity, accounting for approximately 70% of the universe's total mass-energy, appears to counteract gravity, propelling the universe's most massive objects further apart.
Numerous theories attempt to decipher dark energy's properties, one of which, proposed by Albert Einstein, suggests it is a cosmological constant, an unvarying form of energy infused into the fabric of space-time[8]. An alternative theory proposes that dark energy, or quintessence, need not be constant, but a dynamic field that evolves over time. Quintessence can manifest as either repulsive or attractive, depending on its kinetic and potential energy ratio at a given time.
In their study, Steinhardt, Anna Ijjas of New York University, and Cosmin Andrei of Princeton University, project how quintessence's properties might evolve over the next few billion years. Their model proposes that dark energy could currently be in a phase of rapid decay that began potentially billions of years ago.
According to the team's model, after nearly 14 billion years of growth, space might be on the verge of shrinking. This contraction would initially be so slow that it would go unnoticed.
Steinhardt postulates two potential outcomes. Either the universe contracts until it collapses, ending space-time as we know it, or it contracts just enough to return to its original state, leading to another 'Big Bang' or a great "rebound".
The quintessence interpretation is a "perfectly reasonable assumption about what dark energy is," says Hinshaw. But without a good way to test whether quintessence is real or whether cosmic expansion has begun to slow down, for now, it remains a theory fitted to past observations. Whether our universe's future holds infinite growth or rapid decay, only time will tell.
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