Study shows bumble bees 'play'

 Bumble bees play, according to new research led by Queen Mary University of London published in Animal Behaviour. It is the first time that object play behaviour has been shown in an insect, adding to mounting evidence that bees may experience positive 'feelings'.

The team of researchers set up numerous experiments to test their hypothesis, which showed that bumble bees went out of their way to roll wooden balls repeatedly despite there being no apparent incentive for doing so. Three videos of the bees playing are available in the notes to editors below.

The study also found that younger bees rolled more balls than older bees, mirroring human behaviour of young children and other juvenile mammals and birds being the most playful, and that male bees rolled them for longer than their female counterparts.

The study followed 45 bumble bees in an arena and gave them the options of walking through an unobstructed path to reach a feeding area or deviating from this path into the areas with wooden balls. Individual bees rolled balls between 1 and, impressively, 117 times over the experiment. The repeated behaviour suggested that ball-rolling was rewarding.

This was supported by a further experiment where another 42 bees were given access to two coloured chambers, one always containing movable balls and one without any objects. When tested and given a choice between the two chambers, neither containing balls, bees showed a preference for the colour of the chamber previously associated with the wooden balls. The set-up of the experiments removed any notion that the bees were moving the balls for any greater purpose other than play. Rolling balls did not contribute to survival strategies, such as gaining food, clearing clutter, or mating and was done under stress-free conditions.

The research builds on previous experiments from the same lab at Queen Mary, which showed that bumble bees can be taught to score a goal, by rolling a ball to a target, in exchange for a sugary food reward. During the previous experiment, the team observed that bumble bees rolled balls outside of the experiment, without getting any food reward. The new research showed the bees rolling balls repeatedly without being trained and without receiving any food for doing so -- it was voluntary and spontaneous -- therefore akin to play behaviour as seen in other animals.

Study first-author, Samadi Galpayage, PhD student at Queen Mary University of London said: "It is certainly mind-blowing, at times amusing, to watch bumble bees show something like play. They approach and manipulate these 'toys' again and again. It goes to show, once more, that despite their little size and tiny brains, they are more than small robotic beings. They may actually experience some kind of positive emotional states, even if rudimentary, like other larger fluffy, or not so fluffy, animals do. This sort of finding has implications to our understanding of sentience and welfare of insects and will, hopefully, encourage us to respect and protect life on Earth ever more."

River longer than the Thames beneath Antarctic ice sheet could affect ice loss

 An unexpected river under the Antarctic ice sheet affects the flow and melting of ice, potentially accelerating ice loss as the climate warms.

The 460km-long river is revealed in a new study, which details how it collects water at the base of the Antarctic ice sheet from an area the size of Germany and France combined. Its discovery shows the base of the ice sheet has more active water flow than previously thought, which could make it more susceptible to changes in climate.

The discovery was made by researchers at Imperial College London, the University of Waterloo, Canada, Universiti Malaysia Terengganu, and Newcastle University, with the details published today in Nature Geoscience.

Co-author Professor Martin Siegert, from the Grantham Institute at Imperial College London, said: "When we first discovered lakes beneath the Antarctic ice a couple of decades ago, we thought they were isolated from each other. Now we are starting to understand there are whole systems down there, interconnected by vast river networks, just as they might be if there weren't thousands of metres of ice on top of them.

"The region where this study is based holds enough ice to raise the sea level globally by 4.3m. How much of this ice melts, and how quickly, is linked to how slippery the base of the ice is. The newly discovered river system could strongly influence this process."

Water can appear beneath ice sheets in two main ways: from surface meltwater running down through deep crevasses, or by melting at the base, caused by the natural heat of the Earth and friction as the ice moves over land.

However, the ice sheets around the north and south poles have different characteristics. In Greenland, the surface experiences strong melting over the summer months, where immense amounts of water channel down through deep crevasses called moulins.

In Antarctica, however, the surface doesn't melt in sufficient quantities to create moulins, as the summers are still too cold. It was thought this meant that there was relatively little water at the base of the Antarctic ice sheets.

The new discovery turns this idea on its head, showing there is sufficient water from basal melt alone to create huge river systems under kilometres-thick ice.

The discovery was made through a combination of airborne radar surveys that allow researchers to look beneath the ice and modelling of the ice sheet hydrology. The team focussed on a largely inaccessible and understudied area that includes ice from both the East and West Antarctic Ice Sheets and reaches the Weddell Sea.

That such a large system could be undiscovered until now is testament to how much we still need to learn about the continent, says lead researcher Dr Christine Dow from the University of Waterloo.

She said: "From satellite measurements we know which regions of Antarctica are losing ice, and how much, but we don't necessarily know why. This discovery could be a missing link in our models. We could be hugely underestimating how quickly the system will melt by not accounting for the influence of these river systems.

"Only by knowing why ice is being lost can we make models and predictions of how the ice will react in the future under further global heating, and how much this could raise global sea levels."

For example, the newly discovered river emerges into the sea beneath a floating ice shelf - where a glacier extending out from the land is buoyant enough to begin floating on the ocean water. The freshwater from the river however churns up warmer water towards the bottom of the ice shelf, melting it from below.

Co-author Dr Neil Ross, from the University of Newcastle, said: "Previous studies have looked at the interaction between the edges of ice sheets and ocean water to determine what melting looks like. However, the discovery of a river that reaches hundreds of kilometres inland driving some of these processes shows that we cannot understand the ice melt fully without considering the whole system: ice sheet, ocean, and freshwater."

The existence of large under-ice rivers also needs to be taken into account when predicting the possible consequences of climate change in the region. For example, if summers warm enough to cause enough surface melt that the water reaches the base of the ice sheet, it could have large effects on the river systems, potentially tipping Antarctica to a Greenland-like state, where ice loss is much faster.

Trunk dexterity explained: Scientists decipher facial motor control in elephants

 Elephants have an amazing arsenal of face, ear and trunk movements. The trunk consists of far more muscles than the entire human body and can perform both powerful and very delicate movements. A team of scientists from the Humboldt University of Berlin and the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) now examined the facial motor nucleus of African and Asian elephants, the brain structure that controls the facial muscles of these animals. This nucleus contains more facial motor neurons than in any other terrestrial mammal, the scientists show in a paper published in the journal Science Advances. African elephants in particular have particularly prominent neuron clusters for the control of the trunk "fingers."

One of the most remarkable body parts in the animal kingdom is the elephant trunk. It is extremely muscular and strong, containing far more muscles than the entire human body, and yet it is very sensitive and capable of carefully performed, finely tuned motor actions. The way elephants use the tip of their trunk strongly resembles a human hand, and they actually have so-called fingers at the tip. Lena Kaufmann and colleagues in Michael Brecht's laboratory at HU Berlin and Thomas Hildebrandt's Department of Reproduction Management at the Leibniz-IZW for the first time have now studied and described in detail the so-called elephant facial nucleus -- the brain structure responsible for controlling the elephants' facial muscles, from the ears to the tip of the trunk.

"The elephant's facial motor nucleus is unique in several ways. For example, it contains more facial motor neurons than all other terrestrial mammals," says first author Lena Kaufmann (HU Berlin). The scientists counted about 54,000 neurons in the facial nucleus of Asian elephants (Elephas maximus), whereas the African savanna elephant (Loxodonta africana) even has about 63,000. The team attributed the higher number of facial nucleus neurons in African savanna elephants to their larger ears and more elaborate trunk tip. "African savanna elephants have two so-called fingers at the trunk tip with which they grip objects," says Thomas Hildebrandt (Leibniz-IZW). "This kind of pincer grip requires much dexterity with the trunk tip. Not surprisingly, we see in the brains of African elephants prominent neuron clusters for the control of the fingertips." Asian elephants have only one finger and tend to wrap their trunk around objects; hence their finger-tip is less prominently represented in their brain.

"The elephant facial nucleus is one of a kind," says Michael Brecht. "It's not just the huge number of neurons. We also observed size gradients of neurons along the trunk representation that we do not see in other mammals. The observed giant elephant neurons probably arise from the need to extend very long signalling structures into the trunk."

Traces of ancient ocean discovered on Mars

 A recently released set of topography maps provides new evidence for an ancient northern ocean on Mars. The maps offer the strongest case yet that the planet once experienced sea-level rise consistent with an extended warm and wet climate, not the harsh, frozen landscape that exists today.

"What immediately comes to mind as one the most significant points here is that the existence of an ocean of this size means a higher potential for life," said Benjamin Cardenas, assistant professor of geosciences at Penn State and lead author on the study recently published in the Journal of Geophysical Research: Planets. "It also tells us about the ancient climate and its evolution. Based on these findings, we know there had to have been a period when it was warm enough and the atmosphere was thick enough to support this much liquid water at one time."

There has long been debate in the scientific community about whether Mars had an ocean in its low-elevation northern hemisphere, Cardenas explained. Using topography data, the research team was able to show definitive evidence of a roughly 3.5-billion-year-old shoreline with substantial sedimentary accumulation, at least 900 meters thick, that covered hundreds of thousands of square kilometers.

"The big, novel thing that we did in this paper was think about Mars in terms of its stratigraphy and its sedimentary record," Cardenas said. "On Earth, we chart the history of waterways by looking at sediment that is deposited over time. We call that stratigraphy, the idea that water transports sediment and you can measure the changes on Earth by understanding the way that sediment piles up. That's what we've done here -- but it's Mars."

The team used software developed by the United States Geological Survey to map data from the National Aeronautics and Space Administration (NASA) and the Mars Orbiter Laser Altimeter. They discovered over 6,500 kilometers of fluvial ridges and grouped them into 20 systems to show that the ridges are likely eroded river deltas or submarine-channel belts, the remnants of an ancient Martian shoreline.

Elements of rock formations, such as ridge-system thicknesses, elevations, locations and possible sedimentary flow directions helped the team understand the evolution of the region's paleogeography. The area that was once ocean is now known as Aeolis Dorsa and contains the densest collection of fluvial ridges on the planet, Cardenas explained.

"The rocks in Aeolis Dorsa capture some fascinating information about what the ocean was like," he said. "It was dynamic. The sea level rose significantly. Rocks were being deposited along its basins at a fast rate. There was a lot of change happening here."

Cardenas explained that on Earth, the ancient sedimentary basins contain the stratigraphic records of evolving climate and life. If scientists want to find a record of life on Mars, an ocean as big as the one that once covered Aeolis Dorsa would be the most logical place to start.

"A major goal for the Mars Curiosity rover missions is to look for signs of life," Cardenas said. "It's always been looking for water, for traces of habitable life. This is the biggest one yet. It's a giant body of water, fed by sediments coming from the highlands, presumably carrying nutrients. If there were tides on ancient Mars, they would have been here, gently bringing in and out water. This is exactly the type of place where ancient Martian life could have evolved."

Cardenas and his colleagues have mapped what they have determined are other ancient waterways on Mars. An upcoming study in the Journal of Sedimentary Research shows various outcrops visited by Curiosity rover were likely sedimentary strata from ancient river bars. Another paper published in Nature Geoscience applies an acoustic imaging technique used to view stratigraphy beneath the Gulf of Mexico's seafloor to a model of Mars-like basin erosion. The researchers determined the landforms called fluvial ridges, found widely across Mars, are likely ancient river deposits eroded from large basins similar to Aeolis Dorsa.

"The stratigraphy that we're interpreting here is quite similar to stratigraphy on Earth," Cardenas said. "Yes, it sounds like a big claim to say we've discovered records of large waterways on Mars, but in reality, this is relatively mundane stratigraphy. It's textbook geology once you recognize it for what it is. The interesting part, of course, is it's on Mars."

Magma on Mars likely

 Since 2018, when the NASA InSight Mission deployed the SEIS seismometer on the surface of Mars, seismologists and geophysicists at ETH Zurich have been listening to the seismic pings of more than 1,300 marsquakes. Again and again, the researchers registered smaller and larger Mars quakes. A detailed analysis of the quakes' location and spectral character brought a surprise. With epicentres originating in the vicinity of the Cerberus Fossae -- a region consisting of a series of rifts or graben -- these quakes tell a new story. A story that suggests vulcanism still plays an active role in shaping the Martian surface.

Mars shows signs of life and youth

An international team of researchers, led by ETH Zurich, analysed a cluster of more than 20 recent marsquakes that originated in the Cerberus Fossae graben system. From the seismic data, scientists concluded that the low-frequency quakes indicate a potentially warm source that could be explained by present day molten lava, i.e., magma at that depth, and volcanic activity on Mars. Specifically, they found that the quakes are located mostly in the innermost part of Cerberus Fossae.

When they compared seismic data with observational images of the same area, they also discovered darker deposits of dust not only in the dominant direction of the wind, but in multiple directions surrounding the Cerebus Fossae Mantling Unit. "The darker shade of the dust signifies geological evidence of more recent volcanic activity -- perhaps within the past 50,000 years -- relatively young, in geological terms," explains Simon Staehler, the lead author of the paper, which has now been published in the journal Nature. Staehler is a Senior Scientist working in the Seismology and Geodynamics group led by Professor Domenico Giardini at the Institute of Geophysics, ETH Zurich.

Why study the terrestrial neighbour?

Exploring Earth's planetary neighbours is no easy task. Mars is the only planet, other than Earth, in which scientists have ground-based rovers, landers, and now even drones that transmit data. All other planetary exploration, so far, has relied on orbital imagery. "InSight's SEIS is the most sensitive seismometer ever installed on another planet," says Domenico Giardini. "It affords geophysicists and seismologists an opportunity to work with current data showing what is happening on Mars today -- both at the surface and in its interior." The seismic data, along with orbital images, ensures a greater degree of confidence for scientific inferences.

One of our nearest terrestrial neighbours, Mars is important for understanding similar geological processes on Earth. The red planet is the only one we know of, so far, that has a core composition of iron, nickel, and sulphur that might have once supported a magnetic field. Topographical evidence also indicates that Mars once held vast expanses of water and possibly a denser atmosphere. Even today, scientists have learned that frozen water, although possibly mostly dry ice, still exists on its polar caps. "While there is much more to learn, the evidence of potential magma on Mars is intriguing," Anna Mittelholz, Postdoctoral Fellow at ETH Zurich and Harvard University.

Last remnants of geophysical life

Looking at images of the vast dry, dusty Martian landscape it is difficult to imagine that about 3.6 billion years ago Mars was very much alive, at least in a geophysical sense. It spewed volcanic debris for a long enough time to give rise to Tharsis Montes region, the largest volcanic system in our solar system and the Olympus Mons -- a volcano nearly three times the elevation of Mount Everest. The quakes coming from the nearby Cerberus Fossae -- named for a creature from Greek mythology known as the "hell-hound of Hades" that guards the underworld -- suggest that Mars is not quite dead yet. Here the weight of the volcanic region is sinking and forming parallel graben (or rifts) that pull the crust of Mars apart, much like the cracks that appear on the top of a cake while its baking. According to, Staehler "it is possible that what we are seeing are the last remnants of this once active volcanic region or that the magma is right now moving eastward to the next location of eruption."

Scientists discover material that can be made like a plastic but conducts like metal

Generic molecular model 

Scientists with the University of Chicago have discovered a way to create a material that can be made like a plastic, but conducts electricity more like a metal.

The research, published Oct. 26 in Nature, shows how to make a kind of material in which the molecular fragments are jumbled and disordered, but can still conduct electricity extremely well.

This goes against all of the rules we know about for conductivity -- to a scientist, it's kind of seeing a car driving on water and still going 70 mph. But the finding could also be extraordinarily useful; if you want to invent something revolutionary, the process often first starts with discovering a completely new material.

"In principle, this opens up the design of a whole new class of materials that conduct electricity, are easy to shape, and are very robust in everyday conditions," said John Anderson, an associate professor of chemistry at the University of Chicago and the senior author on the study. "Essentially, it suggests new possibilities for an extremely important technological group of materials," said Jiaze Xie (PhD'22, now at Princeton), the first author on the paper.

'There isn't a solid theory to explain this'

Conductive materials are absolutely essential if you're making any kind of electronic device, whether it be an iPhone, a solar panel, or a television. By far the oldest and largest group of conductors is the metals: copper, gold, aluminum. Then, about 50 years ago, scientists were able to create conductors made out of organic materials, using a chemical treatment known as "doping," which sprinkles in different atoms or electrons through the material. This is advantageous because these materials are more flexible and easier to process than traditional metals, but the trouble is they aren't very stable; they can lose their conductivity if exposed to moisture or if the temperature gets too high.

But fundamentally, both of these organic and traditional metallic conductors share a common characteristic. They are made up of straight, closely packed rows of atoms or molecules. This means that electrons can easily flow through the material, much like cars on a highway. In fact, scientists thought a material had to have these straight, orderly rows in order to conduct electricity efficiently.

Then Xie began experimenting with some materials discovered years ago, but largely ignored. He strung nickel atoms like pearls into a string of of molecular beads made of carbon and sulfur, and began testing.

To the scientists' astonishment, the material easily and strongly conducted electricity. What's more, it was very stable. "We heated it, chilled it, exposed it to air and humidity, and even dripped acid and base on it, and nothing happened," said Xie. That is enormously helpful for a device that has to function in the real world.

But to the scientists, the most striking thing was that the molecular structure of the material was disordered. "From a fundamental picture, that should not be able to be a metal," said Anderson. "There isn't a solid theory to explain this."

Xie, Anderson, and their lab worked with other scientists around the university to try to understand how the material can conduct electricity. After tests, simulations, and theoretical work, they think that the material forms layers, like sheets in a lasagna. Even if the sheets rotate sideways, no longer forming a neat lasagna stack, electrons can still move horizontally or vertically -- as long as the pieces touch.

The end result is unprecedented for a conductive material. "It's almost like conductive Play-Doh -- you can smush it into place and it conducts electricity," Anderson said.

The scientists are excited because the discovery suggests a fundamentally new design principle for electronics technology. Conductors are so important that virtually any new development opens up new lines for technology, they explained.

One of the material's attractive characteristics is new options for processing. For example, metals usually have to be melted in order to be made into the right shape for a chip or device, which limits what you can make with them, since other components of the device have to be able to withstand the heat needed to process these materials.

The new material has no such restriction because it can be made at room temperatures. It can also be used where the need for a device or pieces of the device to withstand heat, acid or alkalinity, or humidity has previously limited engineers' options to develop new technology.

 

Less than five hours' sleep a night linked to higher risk of multiple diseases

Alarm clock

 Getting less than five hours of sleep in mid-to-late life could be linked to an increased risk of developing at least two chronic diseases, finds a new study led by UCL researchers.

The research, published in PLOS Medicine, analysed the impact of sleep duration on the health of more than 7,000 men and women at the ages of 50, 60 and 70, from the Whitehall II cohort study.

Researchers examined the relationship between how long each participant slept for, mortality and whether they had been diagnosed with two or more chronic diseases (multimorbidity) -- such as heart disease, cancer or diabetes -- over the course of 25 years.

People who reported getting five hours of sleep or less at age 50 were 20% more likely to have been diagnosed with a chronic disease and 40% more likely to be diagnosed with two or more chronic diseases over 25 years, compared to people who slept for up to seven hours.

Additionally, sleeping for five hours or less at the age of 50, 60, and 70 was linked to a 30% to 40% increased risk of multimorbidity when compared with those who slept for up to seven hours.

Researchers also found that sleep duration of five hours or less at age 50 was associated with 25% increased risk of mortality over the 25 years of follow-up -- which can mainly be explained by the fact that short sleep duration increases the risk of chronic disease(s) that in turn increase the risk of death.

Lead author, Dr Severine Sabia (UCL Institute of Epidemiology & Health, and Inserm, Université Paris Cité) said: "Multimorbidity is on the rise in high income countries and more than half of older adults now have at least two chronic diseases. This is proving to be a major challenge for public health, as multimorbidity is associated with high healthcare service use, hospitalisations and disability.

"As people get older, their sleep habits and sleep structure change. However, it is recommended to sleep for 7 to 8 hours a night -- as sleep durations above or below this have previously been associated with individual chronic diseases.

"Our findings show that short sleep duration is also associated with multimorbidity.

"To ensure a better night's sleep, it is important to promote good sleep hygiene, such as making sure the bedroom is quiet, dark and a comfortable temperature before sleeping. It's also advised to remove electronic devices and avoid large meals before bedtime. Physical activity and exposure to light during the day might also promote good sleep."

As part of the study, researchers also assessed whether sleeping for a long duration, of nine hours or more, affected health outcomes. There was no clear association between long sleep durations at age 50 and multimorbidity in healthy people.

However, if a participant had already been diagnosed with a chronic condition, then long sleep duration was associated with around a 35% increased risk of developing another illness. Researchers believe this could be due to underlying health conditions impacting sleep.

Jo Whitmore, senior cardiac nurse at the British Heart Foundation said: "Getting enough sleep allows your body to rest. There are a host of other ways that poor sleep could increase the risk of heart disease or stroke, including by increasing inflammation and increasing blood pressure.

The most precise accounting yet of dark energy and dark matter

Nebula illustration

 Astrophysicists have performed a powerful new analysis that places the most precise limits yet on the composition and evolution of the universe. With this analysis, dubbed Pantheon+, cosmologists find themselves at a crossroads.

Pantheon+ convincingly finds that the cosmos is composed of about two-thirds dark energy and one-third matter -- mostly in the form of dark matter -- and is expanding at an accelerating pace over the last several billion years. However, Pantheon+ also cements a major disagreement over the pace of that expansion that has yet to be solved.

By putting prevailing modern cosmological theories, known as the Standard Model of Cosmology, on even firmer evidentiary and statistical footing, Pantheon+ further closes the door on alternative frameworks accounting for dark energy and dark matter. Both are bedrocks of the Standard Model of Cosmology but have yet to be directly detected and rank among the model's biggest mysteries. Following through on the results of Pantheon+, researchers can now pursue more precise observational tests and hone explanations for the ostensible cosmos.

"With these Pantheon+ results, we are able to put the most precise constraints on the dynamics and history of the universe to date," says Dillon Brout, an Einstein Fellow at the Center for Astrophysics | Harvard & Smithsonian. "We've combed over the data and can now say with more confidence than ever before how the universe has evolved over the eons and that the current best theories for dark energy and dark matter hold strong."

Brout is the lead author of a series of papers describing the new Pantheon+ analysis, published jointly today in a special issue of The Astrophysical Journal.

Pantheon+ is based on the largest dataset of its kind, comprising more than 1,500 stellar explosions called Type Ia supernovae. These bright blasts occur when white dwarf stars -- remnants of stars like our Sun -- accumulate too much mass and undergo a runaway thermonuclear reaction. Because Type Ia supernovae outshine entire galaxies, the stellar detonations can be glimpsed at distances exceeding 10 billion light years, or back through about three-quarters of the universe's total age. Given that the supernovae blaze with nearly uniform intrinsic brightnesses, scientists can use the explosions' apparent brightness, which diminishes with distance, along with redshift measurements as markers of time and space. That information, in turn, reveals how fast the universe expands during different epochs, which is then used to test theories of the fundamental components of the universe.

The breakthrough discovery in 1998 of the universe's accelerating growth was thanks to a study of Type Ia supernovae in this manner. Scientists attribute the expansion to an invisible energy, therefore monikered dark energy, inherent to the fabric of the universe itself. Subsequent decades of work have continued to compile ever-larger datasets, revealing supernovae across an even wider range of space and time, and Pantheon+ has now brought them together into the most statistically robust analysis to date.

"In many ways, this latest Pantheon+ analysis is a culmination of more than two decades' worth of diligent efforts by observers and theorists worldwide in deciphering the essence of the cosmos," says Adam Riess, one of the winners of the 2011 Nobel Prize in Physics for the discovery of the accelerating expansion of the universe and the Bloomberg Distinguished Professor at Johns Hopkins University (JHU) and the Space Telescope Science Institute in Baltimore, Maryland. Riess is also an alum of Harvard University, holding a PhD in astrophysics.

Brout's own career in cosmology traces back to his undergraduate years at JHU, where he was taught and advised by Riess. There Brout worked with then-PhD-student and Riess-advisee Dan Scolnic, who is now an assistant professor of physics at Duke University and another co-author on the new series of papers.

Several years ago, Scolnic developed the original Pantheon analysis of approximately 1,000 supernovae.

Now, Brout and Scolnic and their new Pantheon+ team have added some 50 percent more supernovae data points in Pantheon+, coupled with improvements in analysis techniques and addressing potential sources of error, which ultimately has yielded twice the precision of the original Pantheon.

"This leap in both the dataset quality and in our understanding of the physics that underpin it would not have been possible without a stellar team of students and collaborators working diligently to improve every facet of the analysis," says Brout.

Taking the data as a whole, the new analysis holds that 66.2 percent of the universe manifests as dark energy, with the remaining 33.8 percent being a combination of dark matter and matter. To arrive at even more comprehensive understanding of the constituent components of the universe at different epochs, Brout and colleagues combined Pantheon+ with other strongly evidenced, independent and complementary measures of the large-scale structure of the universe and with measurements from the earliest light in the universe, the cosmic microwave background.

Another key Pantheon+ result relates to one of the paramount goals of modern cosmology: nailing down the current expansion rate of the universe, known as the Hubble constant. Pooling the Pantheon+ sample with data from the SH0ES (Supernova H0 for the Equation of State) collaboration, led by Riess, results in the most stringent local measurement of the current expansion rate of the universe.

Pantheon+ and SH0ES together find a Hubble constant of 73.4 kilometers per second per megaparsec with only 1.3% uncertainty. Stated another way, for every megaparsec, or 3.26 million light years, the analysis estimates that in the nearby universe, space itself is expanding at more than 160,000 miles per hour.

However, observations from an entirely different epoch of the universe's history predict a different story. Measurements of the universe's earliest light, the cosmic microwave background, when combined with the current Standard Model of Cosmology, consistently peg the Hubble constant at a rate that is significantly less than observations taken via Type Ia supernovae and other astrophysical markers. This sizable discrepancy between the two methodologies has been termed the Hubble tension.

The new Pantheon+ and SH0ES datasets heighten this Hubble tension. In fact, the tension has now passed the important 5-sigma threshold (about one-in-a-million odds of arising due to random chance) that physicists use to distinguish between possible statistical flukes and something that must accordingly be understood. Reaching this new statistical level highlights the challenge for both theorists and astrophysicists to try and explain the Hubble constant discrepancy.

"We thought it would be possible to find clues to a novel solution to these problems in our dataset, but instead we're finding that our data rules out many of these options and that the profound discrepancies remain as stubborn as ever," says Brout.

The Pantheon+ results could help point to where the solution to the Hubble tension lies. "Many recent theories have begun pointing to exotic new physics in the very early universe, however such unverified theories must withstand the scientific process and the Hubble tension continues to be a major challenge," says Brout.

Overall, Pantheon+ offers scientists a comprehensive lookback through much of cosmic history. The earliest, most distant supernovae in the dataset gleam forth from 10.7 billion light years away, meaning from when the universe was roughly a quarter of its current age. In that earlier era, dark matter and its associated gravity held the universe's expansion rate in check. Such state of affairs changed dramatically over the next several billion years as the influence of dark energy overwhelmed that of dark matter. Dark energy has since flung the contents of the cosmos ever-farther apart and at an ever-increasing rate.

"With this combined Pantheon+ dataset, we get a precise view of the universe from the time when it was dominated by dark matter to when the universe became dominated by dark energy," says Brout. "This dataset is a unique opportunity to see dark energy turn on and drive the evolution of the cosmos on the grandest scales up through present time."