Einstein’s gravity endures despite a dark energy puzzle
The DESI project previously reported that dark energy — long thought to be constant — changes over time. A new analysis reaffirms that claim.
An analysis upholds general relativity but hints dark energy may vary over time
Scientists mapped galaxies with the Dark Energy Spectroscopic Instrument at the Mayall telescope (shown) at Kitt Peak National Observatory in Arizona.
T. Slovinský, KPNO/AURA/NSF, NOIRLab
Scientists may o.k. be wrong about dark energy. But they’re right about gravity, a new in sorting out about suggests.
Dark energy, the mysterious phenomenon that causes the expansion of the cosmos to accelerate, is widely thought to have had a relentless density someday of the history of the universe. But dark energy may as a substitute be waning, researchers from the Dark Energy Spectroscopic Instrument, or DESI, collaboration report November 19 in a batch of papers posted to the project’s web pages and arXiv.org.
The finding reaffirms an April report from the same team that had come to a similar conclusion (SN: four/four/24). Simultaneously, the emblem new analysis — a more thorough in sorting out concerning the same data used within the earlier report — confirms that the DESI data agree with general relativity, Albert Einstein’s theory of gravity, without a evidence for alternative, “modified gravity” theories.
DESI makes a 3-d map of galaxies someday of the cosmos. The project’s previous analysis focused best on one sort of knowledge gleaned from that map: baryon acoustic oscillations, sound waves within the early universe that left imprints on the cosmos that may o.k. be visible today (SN: three/four/19).
The new analysis adds information on how galaxies and other structures evolve over cosmic history. “That is the first time we are sensitive to how structure grows with time,” says cosmologist Dragan Huterer of the University of Michigan in Ann Arbor. “That is an exceptionally powerful the reason is, growth of structure is popular to be very sensitive to dark energy and modified gravity.”
In both analyses, the researchers found signs of a variation in dark energy’s equation of state, the relationship between its pressure and density over time. “We are pointing at the same conclusion, and it be … completely reassuring,” says cosmologist Pauline Zarrouk of CNRS and the Laboratoire de Physique Nucléaire et de Hautes Énergies in Paris. This is able to well be why two analyses are according to the same data, “if we were now not seeing the same [conclusion], which may perhaps in point of fact be an argument.” (In both cases, the team combined DESI’s data with other cosmological data, including data on the cosmic microwave background, the oldest light within the universe.)
With the first result, DESI researchers were sticking their necks out, says physicist Daniel Scolnic of Duke University. “They’re now not backing away from that. Kind of about a times when there’s some big bring about cosmology, it looks like a month later … it’s long past.” But with DESI, “their neck’s still out. I in point of fact respect that and appreciate that.”
If dark energy is confirmed to change, it'd send a jolt through cosmology, overthrowing scientists’ accepted theory, the same old cosmological model. That theory has been extremely a success at describing the cosmos, nonetheless it includes poorly understood components, like dark energy and the likewise unidentified source of mass which is regularly called dark matter (SN: eight/26/24).
In an attempt at a more satisfying explanation of the cosmos, some scientists are tweaking general relativity, which describes gravity brought on by mass warping spacetime. Modified gravity theories may in all probability potentially eliminate the need for dark matter or dark energy (SN: 7/5/24). Nonetheless it the structure formation that DESI observed turned into in accordance with that predicted by general relativity. And there’s no evidence for modified gravity, though the theories are not fully ruled out.
Within the emblem new in sorting out about, a puzzle persists concerning the masses of neutrinos, lightweight subatomic particles that may o.k. be plentiful within the cosmos. Like DESI’s first analysis, the emblem new findings indicate that the sum of the masses of the three types of neutrinos is smaller than expected, not not as much as by some accounts (SN: 9/20/24). That may perhaps hint that cosmologists have misunderstood something concerning the character of the cosmos or about neutrinos themselves.
In 2025, the DESI collaboration plans to free up results according to the project’s first three years of knowledge. That may perhaps even be a true test of how robust the implications are, including whether dark energy indeed changes over time.
Scolnic envisions the same old cosmological model as a bonfire. While scientists had been enjoying sitting across the nice and cozy glow, with the DESI results, sparks have begun to fly. “That is while you tell everyone, ‘Let’s just take a step back from the bonfire, simply to be safe. … We’re now not throwing water on the total thing, but definitely only 1 step back.’”
More Stories from Science News on Cosmology
What's Your Reaction?
