Physicists believe they have detected a striking asymmetry in the arrangements of galaxies in the sky. If confirmed, the finding would point to features of the unknown fundamental laws that operated during the Big Bang.
“If this result is real, someone’s going to get a Nobel Prize,” said Marc Kamionkowski, a physicist at Johns Hopkins University who was not involved in the analysis.
As if playing a cosmic game of Connect the Dots, the researchers drew lines between sets of four galaxies, constructing four-cornered shapes called tetrahedra. When they had built every possible tetrahedron from a catalog of 1 million galaxies, they found that tetrahedra oriented one way outnumber their mirror images.
A hint of the imbalance between tetrahedra and their mirror images was first reported by Oliver Philcox, an astrophysicist at Columbia University in New York, in a paper published in Physical Review D in September. In an independent analysis conducted simultaneously that’s now undergoing peer review, Jiamin Hou and Zachary Slepian of the University of Florida and Robert Cahn of Lawrence Berkeley National Laboratory detected the asymmetry with a level of statistical certainty that physicists usually consider definitive.
But with such a blockbuster finding — and one that’s still under review — experts say caution is warranted.
“There’s no obvious reason that they’ve made a mistake,” said Shaun Hotchkiss, a cosmologist at the University of Auckland. “That doesn’t mean that there isn’t a mistake.”
The putative imbalance violates a symmetry called “parity,” an equivalence of left and right. If the observation withstands scrutiny, physicists think it must reflect an unknown, parity-violating ingredient in the primordial process that sowed the seeds of all the structure that developed in our universe.
“It’s an incredible result — really impressive,” Kamionkowski said. “Do I believe it? I’m going to wait to really celebrate.”
Left-Handed Universe
Parity was once a cherished symmetry of physics. But then, in 1957, the Chinese American physicist Chien-Shiung Wu’s nuclear decay experiments revealed that our universe indeed has a slight handedness to it: Subatomic particles involved in the weak nuclear force, which causes nuclear decay, are always magnetically oriented in the opposite direction from the one they move in, so that they spiral like the threads of a left-handed screw. The mirror-image particles — the ones like right-handed screws — don’t feel the weak force.
Wu’s revelation was shocking. “We are all rather shaken by the death of our well-beloved friend, parity,” the physicist John Blatt wrote in a letter to Wolfgang Pauli.
The left-handedness of the weak force has subtle effects that couldn’t have influenced the cosmos on galactic scales. But ever since Wu’s discovery, physicists have sought other ways in which the universe differs from its mirror image.
If, for instance, some primordial parity violation was in effect when the universe was in its infancy, it might have imprinted a twist onto the structure of the cosmos.
At or near the time of the universe’s birth, a field known as the inflaton is thought to have permeated space. A roiling, boiling medium where inflaton particles continuously bubbled up and disappeared, the inflaton field was also repulsive; for the brief time it may have existed, it would have caused our universe to rapidly expand to 100 trillion trillion times its original size. All of those quantum fluctuations of particles in the inflaton field were flung outward and frozen into the cosmos, becoming variations in the density of matter. The denser pockets continued to gravitationally coalesce to produce the galaxies and large-scale structure we see today.
In 1999, researchers including Kamionkowski considered what would happen if more than one field was present before this explosion. The inflaton field could have interacted with another field that could produce right-handed and left-handed particles. If the inflaton treated right-handed particles differently than the left-handed ones, then it could have preferentially created particles of one handedness over the other. This so-called Chern-Simons coupling would have imbued the early quantum fluctuations with a preferred handedness, which would have evolved into an imbalance of left-handed and right-handed tetrahedral arrangements of galaxies.
As for what the additional field might be, one possibility is the gravitational field. In this scenario, a parity-violating Chern-Simons interaction would occur between inflaton particles and gravitons — the quantum units of gravity — which would have popped up in the gravitational field during inflation. Such an interaction would have created a handedness in the density variations of the early universe and, consequently, in today’s large-scale structure.
Introduction
In 2006, Stephon Alexander, a physicist now at Brown University, suggested that Chern-Simons gravity could also potentially solve one of the biggest mysteries in cosmology: why our universe contains more matter than antimatter. He surmised that the Chern-Simons interaction could have yielded a relative abundance of left-handed gravitons, which would in turn preferentially create left-handed matter over right-handed antimatter.
Alexander’s idea remained relatively obscure for years. When he heard about the new findings, he said, “that was a big surprise.”
Tetrahedra in the Sky
Cahn thought the possibility of solving the matter-antimatter asymmetry puzzle with parity violation in the early universe was “speculative, but also provocative.” In 2019, he decided to look for parity violation in a catalog of galaxies in the Sloan Digital Sky Survey. He didn’t expect to find anything but thought it would be worth a check.
To test whether the galaxy distribution respects or violates parity, he and his collaborators knew they needed to study tetrahedral arrangements of four galaxies. This is because the tetrahedron is the simplest three-dimensional shape, and only 3D objects have a chance at violating parity. To understand this, consider your hands. Because hands are 3D, there’s no way to rotate a left one to make it look like a right one. Flip your left hand over so that the thumbs of both hands are on the left, and your hands still look different — the palms face opposite ways. By contrast, if you trace a left hand on a sheet of paper and cut out the 2D image, flipping the cutout over makes it look like a right hand. The cutout and its mirror image are indistinguishable.
In 2020, Slepian and Cahn came up with a way of defining the “handedness” of a tetrahedral arrangement of galaxies in order to compare the number of left-handed and right-handed ones in the sky. First they took a galaxy and looked at the distances to three other galaxies. If the distances increased in the clockwise direction like a right-handed screw, they called the tetrahedron right-handed. If the distances increased going counterclockwise, it was left-handed.
To determine whether the universe as a whole has a preferred handedness, they had to repeat the analysis for all tetrahedra constructed from their database of 1 million galaxies. There are nearly 1 trillion trillion such tetrahedra — an intractable list to handle one at a time. But a factoring trick developed in earlier work on a different problem allowed the researchers to look at the parity of tetrahedra more holistically: Rather than assembling one tetrahedron at a time and determining its parity, they could take each galaxy in turn and group all other galaxies according to their distances from that galaxy, creating layers like the layers of an onion. By expressing the relative positions of galaxies in each layer in terms of mathematical functions of angles called spherical harmonics, they could systematically combine sets of three layers to make collective tetrahedra.
The researchers then compared the results to their expectations based on parity-preserving laws of physics. Hou led this step, analyzing fake catalogs of galaxies that had been generated by simulating the evolution of the universe starting from tiny, parity-preserving density variations. From these mock catalogs, Hou and her colleagues could determine how the tally of left- and right-handed tetrahedra randomly varies, even in a mirror-symmetric world.
The team found a “seven-sigma” level of parity violation in the real data, meaning that the imbalance between left- and right-handed tetrahedra was seven times as large as could be expected from random chance and other conceivable sources of error.
Kamionkowski called it “incredible that they were able to do that,” adding that “technically, it’s absolutely astounding. It’s a really, really, really complicated analysis.”
Philcox used similar methods (and had co-authored some earlier papers proposing such an analysis with Hou, Slepian and Cahn), but he made some different choices — for example, grouping the galaxies into fewer layers than Hou and colleagues, and omitting some problematic tetrahedra from the analysis — and therefore found a more modest 2.9-sigma violation of parity. The researchers are now studying the differences between their analyses. Even after extensive efforts to understand the data, all parties remain cautious.
Corroborating Evidence
The surprising finding hints at new physics that could potentially answer long-standing questions about the universe. But the work has only just begun.
First physicists need to verify (or falsify) the observation. New, ambitious galaxy surveys on which to repeat the analysis are already underway. The ongoing Dark Energy Spectroscopic Instrument survey, for instance, has logged 14 million galaxies so far and will contain more than 30 million when it’s completed. “That’ll give us an opportunity to look at this in much greater detail with much better statistics,” said Cahn.
Introduction
Moreover, if the parity-violating signal is real, it could show up in data other than the distribution of galaxies. The oldest light in the sky, for example — a bath of radiation known as the cosmic microwave background, left over from the early universe — provides our earliest snapshot of spatial variations in the cosmos. The dappled pattern of this light should contain the same parity-violating correlations as the galaxies that formed later. Physicists say it should be possible to find such a signal in the light.
Another place to look will be the pattern of gravitational waves that may have been generated during inflation, called the stochastic gravitational wave background. These corkscrew-like ripples in the space-time fabric can be right-handed or left-handed, and in a parity-preserving world, they would contain equal amounts of each. So if physicists manage to measure this background and find that one handedness is favored, this would be an unambiguous, independent check of parity-violating physics in the early universe.
As the search for corroborating evidence begins, theorists will study models of inflation that could have produced the signal. With Giovanni Cabass, a theoretical physicist at the Institute for Advanced Study in Princeton, New Jersey, Philcox recently used his measurement to test a slew of parity-violating models of inflation, including those of the Chern-Simons type. (They can’t yet say with certainty which model, if any, is correct.)
Alexander has also refocused his efforts on understanding Chern-Simons gravity. With collaborators including Kamionkowski and Cyril Creque-Sarbinowski of the Flatiron Institute’s Center for Computational Astrophysics, Alexander has begun working out subtle details about how Chern-Simons gravity in the early universe would influence the distribution of today’s galaxies.
“I was kind of like the lone soldier pushing this stuff for a while,” he said. “It’s good to see people taking an interest.”
Editor’s Note: The Flatiron Institute is funded by the Simons Foundation, which also supports this editorially independent magazine. In addition, Oliver Philcox receives funding from the Simons Foundation.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
The European Space Agency is fast-tracking a new mission called Ramses, which will fly to near-Earth asteroid 99942 Apophis and join the space rock in 2029 when it comes very close to our planet — closer even than the region where geosynchronous satellites sit.
Ramses is short for Rapid Apophis Mission for Space Safety and, as its name suggests, is the next phase in humanity’s efforts to learn more about near-Earth asteroids (NEOs) and how we might deflect them should one ever be discovered on a collision course with planet Earth.
In order to launch in time to rendezvous with Apophis in February 2029, scientists at the European Space Agency have been given permission to start planning Ramses even before the multinational space agency officially adopts the mission. The sanctioning and appropriation of funding for the Ramses mission will hopefully take place at ESA’s Ministerial Council meeting (involving representatives from each of ESA’s member states) in November of 2025. To arrive at Apophis in February 2029, launch would have to take place in April 2028, the agency says.
This is a big deal because large asteroids don’t come this close to Earth very often. It is thus scientifically precious that, on April 13, 2029, Apophis will pass within 19,794 miles (31,860 kilometers) of Earth. For comparison, geosynchronous orbit is 22,236 miles (35,786 km) above Earth’s surface. Such close fly-bys by asteroids hundreds of meters across (Apophis is about 1,230 feet, or 375 meters, across) only occur on average once every 5,000 to 10,000 years. Miss this one, and we’ve got a long time to wait for the next.
When Apophis was discovered in 2004, it was for a short time the most dangerous asteroid known, being classified as having the potential to impact with Earth possibly in 2029, 2036, or 2068. Should an asteroid of its size strike Earth, it could gouge out a crater several kilometers across and devastate a country with shock waves, flash heating and earth tremors. If it crashed down in the ocean, it could send a towering tsunami to devastate coastlines in multiple countries.
Over time, as our knowledge of Apophis’ orbit became more refined, however, the risk of impact greatly went down. Radar observations of the asteroid in March of 2021 reduced the uncertainty in Apophis’ orbit from hundreds of kilometers to just a few kilometers, finally removing any lingering worries about an impact — at least for the next 100 years. (Beyond 100 years, asteroid orbits can become too unpredictable to plot with any accuracy, but there’s currently no suggestion that an impact will occur after 100 years.) So, Earth is expected to be perfectly safe in 2029 when Apophis comes through. Still, scientists want to see how Apophis responds by coming so close to Earth and entering our planet’s gravitational field.
Breaking space news, the latest updates on rocket launches, skywatching events and more!
“There is still so much we have yet to learn about asteroids but, until now, we have had to travel deep into the solar system to study them and perform experiments ourselves to interact with their surface,” said Patrick Michel, who is the Director of Research at CNRS at Observatoire de la Côte d’Azur in Nice, France, in a statement. “Nature is bringing one to us and conducting the experiment itself. All we need to do is watch as Apophis is stretched and squeezed by strong tidal forces that may trigger landslides and other disturbances and reveal new material from beneath the surface.”
The Goldstone radar’s imagery of asteroid 99942 Apophis as it made its closest approach to Earth, in March 2021. (Image credit: NASA/JPL–Caltech/NSF/AUI/GBO)
By arriving at Apophis before the asteroid’s close encounter with Earth, and sticking with it throughout the flyby and beyond, Ramses will be in prime position to conduct before-and-after surveys to see how Apophis reacts to Earth. By looking for disturbances Earth’s gravitational tidal forces trigger on the asteroid’s surface, Ramses will be able to learn about Apophis’ internal structure, density, porosity and composition, all of which are characteristics that we would need to first understand before considering how best to deflect a similar asteroid were one ever found to be on a collision course with our world.
Besides assisting in protecting Earth, learning about Apophis will give scientists further insights into how similar asteroids formed in the early solar system, and, in the process, how planets (including Earth) formed out of the same material.
One way we already know Earth will affect Apophis is by changing its orbit. Currently, Apophis is categorized as an Aten-type asteroid, which is what we call the class of near-Earth objects that have a shorter orbit around the sun than Earth does. Apophis currently gets as far as 0.92 astronomical units (137.6 million km, or 85.5 million miles) from the sun. However, our planet will give Apophis a gravitational nudge that will enlarge its orbit to 1.1 astronomical units (164.6 million km, or 102 million miles), such that its orbital period becomes longer than Earth’s.
It will then be classed as an Apollo-type asteroid.
Ramses won’t be alone in tracking Apophis. NASA has repurposed their OSIRIS-REx mission, which returned a sample from another near-Earth asteroid, 101955 Bennu, in 2023. However, the spacecraft, renamed OSIRIS-APEX (Apophis Explorer), won’t arrive at the asteroid until April 23, 2029, ten days after the close encounter with Earth. OSIRIS-APEX will initially perform a flyby of Apophis at a distance of about 2,500 miles (4,000 km) from the object, then return in June that year to settle into orbit around Apophis for an 18-month mission.
Related Stories:
Furthermore, the European Space Agency still plans on launching its Hera spacecraft in October 2024 to follow-up on the DART mission to the double asteroid Didymos and Dimorphos. DART impacted the latter in a test of kinetic impactor capabilities for potentially changing a hazardous asteroid’s orbit around our planet. Hera will survey the binary asteroid system and observe the crater made by DART’s sacrifice to gain a better understanding of Dimorphos’ structure and composition post-impact, so that we can place the results in context.
The more near-Earth asteroids like Dimorphos and Apophis that we study, the greater that context becomes. Perhaps, one day, the understanding that we have gained from these missions will indeed save our planet.
