Dark Energy’s Waning? The Big Crunch Hype and Why It’s Probably Not Happening

Below is a blog-style post about the recent study on dark energy suggesting a potential slowing of the universe’s expansion and a possible “Big Crunch,” followed by an explanation of why this scenario remains implausible based on current evidence and scientific consensus. 

The piece draws on recent findings from the Dark Energy Spectroscopic Instrument (DESI) collaboration, as reported in 2024 and 2025, and critiques the interpretation using established cosmological understanding.

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Dark Energy’s Waning? The Big Crunch Hype and Why It’s Probably Not Happening

In March 2025, headlines buzzed with a cosmic twist: dark energy, the mysterious force driving the universe’s accelerating expansion, might be weakening. According to the Dark Energy Spectroscopic Instrument (DESI) team at Arizona’s Kitt Peak National Observatory, their latest data—mapping 6.4 million galaxies—hints that this enigmatic energy peaked billions of years ago and is now fading. Some cosmologists, like Carlos Frenk from Durham University, speculate this could flip the universe’s fate from endless expansion to a dramatic collapse—a “Big Crunch,” where everything implodes back into a hot, dense point, reversing the Big Bang. It’s a wild idea, stirring visions of cosmic Ragnarök. But hold the doomsday headlines—here’s why the Big Crunch remains a long shot, despite the buzz.

The DESI Discovery: What’s New?

DESI’s been peering into the universe’s past with its 5,000 robotic eyes, building the largest 3D map of galaxies ever. By analyzing light from objects 8 to 11 billion years old, they’ve tracked how fast the universe expanded over time via “redshift”—the stretching of light as space grows. The standard model, Lambda Cold Dark Matter (LCDM), assumes dark energy is a constant force (the cosmological constant, or “lambda”), pushing galaxies apart at an ever-faster clip. But DESI’s first-year data, released in 2024 and refined by early 2025, suggests dark energy might not be steady. Instead, it could be “quintessence”—a dynamic field that changes over time.

The numbers are intriguing: DESI claims dark energy hit a peak when the universe was about 70% of its current age (roughly 9.6 billion years ago) and has since dropped by about 10%. If true, the expansion rate, while still accelerating, might be easing off. Extrapolate further, some say, and if dark energy dips below zero into “phantom” territory (a negative, attractive force), gravity could take over, pulling the universe back into a crunch. A Guardian piece from March 19, 2025, quotes Frenk: “I’m much more at ease with the possibility of new universes emerging in due course” via a crunch-and-rebirth cycle. It’s bold, but the data’s not a slam dunk.

The Big Crunch: A Cosmic Comeback?

The Big Crunch isn’t new—it was a contender before 1998, when scientists thought gravity might eventually halt and reverse the universe’s expansion. That changed when supernova observations (led by Perlmutter, Schmidt, and Riess, Nobel Prize 2011) showed the expansion speeding up, pinning the blame on dark energy. The LCDM model took hold: 70% dark energy, 25% dark matter, 5% normal stuff, with dark energy as a constant pushing forever outward. A Big Crunch would need dark energy to fade dramatically—or turn negative—letting gravity win the tug-of-war. DESI’s findings tease that possibility, but let’s unpack why it’s likely overhyped.

Why the Big Crunch Is Implausible

1. Statistical Weakness
   • DESI’s results don’t hit the “five-sigma” threshold—the gold standard for a physics discovery. As The Guardian notes, it’s a “deeply intriguing” signal, not a confirmed shift. Alexie Leauthaud-Harnett from UC Santa Cruz calls it exciting but preliminary. With only one year of a five-year survey analyzed, the data’s robust (1% precision for 8-11 billion years ago), but combining it with older datasets (e.g., supernovae) to suggest waning dark energy is statistically shaky. Cosmologist Paul Steinhardt, in a May 2024 Quanta Magazine piece, argues a quintessence model fits without needing phantom energy—a simpler tweak that doesn’t demand a crunch.
2. Dark Energy’s Dominance
   • Dark energy makes up ~70% of the universe’s mass-energy density, dwarfing matter’s pull. Even if it’s weakened 10%, it’s still driving acceleration—DESI doesn’t dispute that. For a Big Crunch, it’d need to drop far below zero, flipping to an attractive force. No known mechanism supports this. The cosmological constant, backed by decades of supernova and cosmic microwave background (CMB) data from NASA’s WMAP and Planck missions, holds steady. A Big Think article from 2022 stresses: “The reverse, a Big Crunch, isn’t how it’ll end” unless dark energy’s nature radically changes—something DESI doesn’t prove.
3. Quintessence vs. Phantom Energy
   • DESI floats quintessence—a fluctuating dark energy—as a better fit than a constant. But phantom energy (negative density) is a leap beyond that, and theorists like Marina Cortês in Quanta (August 2024) call it “weird” and unlikely. Alternative models by Kim Berghaus and others fit DESI’s data without crossing into collapse territory. The universe could slow its acceleration without reversing—ending in a “Big Freeze” (expansion forever) or a steady state, not a crunch.
4. Cosmic History Says No
   • The universe expanded slower early on, dominated by matter’s gravity, then sped up ~6 billion years ago as dark energy took over (per NASA’s Science site, 2024). DESI’s hint of a 10% dip doesn’t undo this trend—expansion’s still outpacing gravity. A Big Crunch needs a total reversal, but 13.8 billion years of data (CMB, supernovae, galaxy clusters) align with LCDM’s outward push. A Space.com piece (April 2024) notes DESI’s shift would be “revolutionary if confirmed,” but four more years of data are needed to settle it.
5. Testing Troubles
   • Gary Hinshaw, in a 2022 ScienceAlert interview, says quintessence theories are “impossible to test” directly now. We’d need to watch dark energy evolve over eons—beyond our lifespan. DESI’s map is a snapshot, not a movie. Without a clear mechanism for dark energy to nosedive, the Big Crunch stays speculative. Sean Carroll told Nature in 2020: “If dark energy is quintessence, its push could wither,” but could is not will.

The Real Story: Caution, Not Crunch

DESI’s work is groundbreaking—its precision and scale are unmatched, and it’s shaking up LCDM’s edges. A waning dark energy would be huge, as The Guardian suggests, potentially “the first substantial change in decades” to our cosmic model. But implausible doesn’t mean impossible—just unlikely. The Big Crunch grabs headlines (who doesn’t love an end-of-the-world twist?), but the data leans toward subtler shifts: maybe a slower acceleration, not a collapse. Future DESI results, plus NASA’s upcoming Nancy Grace Roman Space Telescope (launching 2027), will refine this picture.

For now, the universe isn’t folding up shop. It’s more likely to stretch on, cooling into a sparse, dark expanse—the Big Freeze—than to slam shut. The St. Joseph Staircase isn’t a miracle; neither is DESI’s hint a crunch guarantee. It’s a marvel of science, not a sign of doom. So, enjoy the cosmic dance—it’s still got a lot of steps left.

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Sources

• Space.com, “Dark Energy Could Be Getting Weaker,” April 16, 2024.
• The Guardian, “Dark Energy Mysterious Cosmic Force Appears to Be Weakening,” March 19, 2025.
• Big Think, “Dark Energy Is Here to Stay, and a ‘Big Crunch’ Isn’t Coming,” May 25, 2022.
• Quanta Magazine, “Waning Dark Energy May Evade ‘Swampland,’” August 19, 2024.
• NASA Science.nasa.gov, “What Is Dark Energy?” February 5, 2024.
• ScienceAlert, “Universe Could Start Shrinking ‘Remarkably’ Soon,” May 2, 2022.
• Nature (via Carroll quote), 2020.