A new possible explanation for the Hubble tension

The universe is expanding. How fast it does so is described by the so-called Hubble-Lemaitre constant. But there is a dispute about how big this constant actually is: Different measurement methods provide contradictory values. This so-called "Hubble tension" poses a puzzle for cosmologists. Researchers from the Universities of Bonn and St. Andrews are now proposing a new solution: Using an alternative theory of gravity, the discrepancy in the measured values can be easily explained -- the Hubble tension disappears. The study has now been published in the Monthly Notices of the Royal Astronomical Society (MNRAS).

The expansion of the universe causes the galaxies to move away from each other.

The speed at which they do this is proportional to the distance between them.

For instance, if galaxy A is twice as far away from Earth as galaxy B, its distance from us also grows twice as fast.

The US astronomer Edwin Hubble was one of the first to recognize this connection.

In order to calculate how fast two galaxies are moving away from each other, it is therefore necessary to know how far apart they are.

However, this also requires a constant by which this distance must be multiplied.

This is the so-called Hubble-Lemaitre constant, a fundamental parameter in cosmology.

Its value can be determined, for example, by looking at the very distant regions of the universe.

This gives a speed of almost 244,000 kilometers per hour per megaparsec distance (one megaparsec is just over three million light years).

244.000 kilometers per hour per megaparsec -- or 264,000?

"But you can also look at celestial bodies that are much closer to us -- so-called category 1a supernovae, which are a certain type of exploding star," explains Prof.

Dr. Pavel Kroupa from the Helmholtz Institute of Radiation and Nuclear Physics at the University of Bonn.

It is possible to determine the distance of a 1a supernova to Earth very precisely.

We also know that shining objects change color when they move away from us -- and the faster they move, the stronger the change.

This is similar to an ambulance, whose siren sounds deeper as it moves away from us.

If we now calculate the speed of the 1a supernovae from their color shift and correlate this with their distance, we arrive at a different value for the Hubble-Lemaitre constant -- namely just under 264,000 kilometers per hour per megaparsec distance.

"The universe therefore appears to be expanding faster in our vicinity -- that is, up to a distance of around three billion light years -- than in its entirety," says Kroupa.

"And that shouldn't really be the case."

However, there has recently been an observation that could explain this.

According to this, the Earth is located in a region of space where there is relatively little matter -- comparable to an air bubble in a cake.

The density of matter is higher around the bubble. Gravitational forces emanate from this surrounding matter, which pull the galaxies in the bubble towards the edges of the cavity.

"That's why they are moving away from us faster than would actually be expected," explains Dr. Indranil Banik from St. Andrews University.

The deviations could therefore simply be explained by a local "under-density."

In fact, another research group recently measured the average speed of a large number of galaxies that are 600 million light years away from us. "It was found that these galaxies are moving away from us four times faster than the standard model of cosmology allows," explains Sergij Mazurenko from Kroupa's research group, who was involved in the current study.

Bubble in the dough of the universe

This is because the standard model does not provide for such under-densities or "bubbles" -- they should not actually exist.

Instead, matter should be evenly distributed in space. If this were the case, however, it would be difficult to explain which forces propel the galaxies to their high speed.

"The standard model is based on a theory of the nature of gravity put forward by Albert Einstein," says Kroupa.

"However, the gravitational forces may behave differently than Einstein expected." The working groups from the Universities of Bonn and St. Andrews have used a modified theory of gravity in a computer simulation.

This "modified Newtonian dynamics" (abbreviation: MOND) was proposed four decades ago by the Israeli physicist Prof.

Dr. Mordehai Milgrom. It is still considered an outsider theory today.

"In our calculations, however, MOND does accurately predict the existence of such bubbles," says Kroupa.

If one were to assume that gravity actually behaves according to Milgrom's assumptions, the Hubble tension would disappear: There would actually only be one constant for the expansion of the universe, and the observed deviations would be due to irregularities in the distribution of matter.

Read more at Science Daily

New research explores future limits of survival and livability in extreme heat conditions

Commonly associated with longer days and slower paces, this summer's record-smashing heat in Arizona demonstrated a concerning future for the planet's warmest season. From power outages endangering entire neighborhoods and heat-related deaths rising among some of the state's most vulnerable populations, the city of Phoenix found itself in national headlines. As national attention grew, one question became clear: How does anyone live there?

The consequences of extreme heat do not affect Arizona residents alone.

Extreme heat made worldwide news this year, including in November when a 23-year-old woman died of cardiorespiratory arrest at a Taylor Swift concert in Brazil where heat indexes that day exceeded 120 degrees.

Jennifer Vanos, associate professor in the School of Sustainability at Arizona State University, studies extreme heat and its health impacts.

She is the lead author of a new paper published Nov. 29 in Nature Communications. Titled "A physiological approach for assessing human survivability and liveability to heat in a changing climate," the paper explores temperatures at which humans can survive.

The research demonstrates that the current estimated upper temperature and humidity limits used for human survivability may not paint an accurate picture of the impacts of a warming planet on human health.

"For the past decade or so we have been using what we call a 'wet bulb temperature' of 35 degrees Celsius, or 95 degrees Fahrenheit, as the limit for human survivability," said Vanos, also a Senior Global Futures Scientist in the Julie Ann Wrigley Global Futures Laboratory.

The wet-bulb temperature limit for human survival indicates the maximum combinations of temperature and humidity that humans can tolerate without suffering inevitable heat stroke over a fixed duration of exposure.

"The idea is that you could survive for up to six hours at that level of heat exposure," Vanos said.

"That number really oversimplifies what happens physiologically in the body when your body is exposed to that temperature, and it doesn't account for important variables like age or other vulnerability factors."

Vanos said the commonly-used wet-bulb temperature for human survivability assumes the person is indoors or shaded, unclothed, completely sedentary, fully heat acclimatized and of an "average size." These assumptions do not align, in most cases, with how humanity navigates the summer season.

The paper models scenarios that adjust for factors such as humidity, age, activity level and sun exposure, and provides a range of safe temperatures based on a series of characteristics.

"We didn't only want to better understand the conditions that people could survive in," Vanos said.

"We wanted to understand the conditions that allowed people to live their lives. If the only safe way to live in an area is to be completely sedentary, people won't want to live there. Being able to spend time outdoors and live your life without seeing a sustained rise in core temperature is a really important metric to understand today and as we move into the future."

Vanos said Gisel Guzman Echavarria, an ASU student, was instrumental in creating the figures used throughout the paper to demonstrate the research findings.

The research, funded by the National Science Foundation, was conducted by a combination of climate scientists and physiologists, a collaboration that Vanos said was crucial in understanding the intertwined nature of heat and human health.

Ollie Jay, professor and director of the Heat and Health Research Incubator at the University of Sydney, said the combined perspectives allow for a cohesive understanding of exactly how climate outcomes can impact people on the physiological and biophysical level.

"The existing wet-bulb temperature estimate of 35 degrees Celsius is used very commonly, with one example being the Intergovernmental Panel on Climate Change report," said Jay, senior author of the paper.

"These kinds of reports can shape policy efforts, but they are using a model for heat that is a very conservative estimate of what the impacts are going to be on humans. If we start using a more realistic, human-based model, the impacts are going to be more severe. They're going to be more widespread and they're going to happen sooner than we are projecting."

Vanos and Jay agree that the survivability ranges provided in the paper can give an important glimpse into the future: one that includes an increased need for cooling infrastructure, a personalized approach to heat protection and possible heat-driven migration.

Read more at Science Daily

Consensus needed on when global warming reaches 1.5°C

Writing in the journal Nature ahead of COP28, a team of Met Office scientists has emphasised that -- surprisingly -- there is currently no formally agreed way of defining the current level of global warming relevant to the Paris Agreement.

They have proposed a solution.

While the global average temperature in a particular year is well-known, this will not be suitable as an indicator of whether the "Paris 1.5" has been breached or not, because the Paris Agreement refers to long-term warming, not individual years.

But no alternative has yet been formally agreed.

Without an agreement on what will count as breaching the Paris 1.5, there may be confusion and delay in responding.

Professor Richard Betts MBE, of the Met Office and the University of Exeter, is the paper's lead author.

He said: "Clarity on breaching the Paris Agreement guard rails will be crucial.

"Without an agreement on what actually will count as exceeding 1.5°C, we risk distraction and confusion at precisely the time when action to avoid the worst effects of climate change becomes even more urgent."

New indicators for global warming levels

Some of the current suggested metrics rely on long-term averages -- usually over two decades -- of annual global annual temperature.

Professor Betts added: "Using the average global temperature over the last 20 years would mean we would have to wait ten years to confirm whether the 1.5 °C ceiling has been reached: creating a decade of otherwise preventable delay.

"Today we are recommending an indicator combining the last ten years of global temperature observations with an estimate of the projection or forecast for the next ten years.

"If adopted, this could mean a universally agreed measure of global warming that could trigger immediate action to avoid further rises."

Using this suggested approach, the researchers found that the figure for the current global warming level is around 1.26°C, with an uncertainty range of 1.13°C to 1.43°C.

It is more likely than not one of the next five years will reach or even exceed 1.5°C above pre-industrial levels.

But even an anomalously warm year would not mean that we have reached the first of the Paris Agreement guard rails.

The Earth's climate system has a range of natural variability where the annual temperature fluctuates within small margins.

Professor Betts added: "Using an indicator of several years of observations and projections will smooth out the natural variation to reveal the underlying human-induced warming."

2023 global temperature

Provisional estimates of the global average surface temperature for 2023 suggest the year could be on track to be the warmest on record.

The year is likely to exceed the level reached in 2016; currently the warmest year on record.

2023 is expected to continue the run of the warmest years on record since 1850.

Beginning in 2015, the series includes years at both ends of natural climate variability.

Some years, like 2016 and 2023, will have been naturally warmer because of the influence of El Niño -- when a natural warming of parts of the tropical Pacific warms the planet temporarily by a small margin.

But the series also includes years which should have been naturally marginally cooler.

Professor Betts concluded: "The fact that the warmest years on record include both the highs and lows of natural climate variability is yet more evidence that climate change driven by human-induced greenhouse gas emissions dominates the recent climate record."

Global warming dashboard

To complement the newly proposed indicators, a new section has been added to the Met Office Climate Dashboard to illustrate the current level of global warming.

The 'Indicators of Global Warming' dashboard displays eight separate indicators as well as observed global mean temperature using Met Office HadCRUT5 data.

Read more at Science Daily

Human behavior guided by fast changes in dopamine levels

What happens in the human brain when we learn from positive and negative experiences? To help answer that question and better understand decision-making and human behavior, scientists are studying dopamine.

Dopamine is a neurotransmitter produced in the brain that serves as a chemical messenger, facilitating communication between nerve cells in the brain and the body. It is involved in functions such as movement, cognition and learning. While dopamine is most known for its association with positive emotions, scientists are also exploring its role in negative experiences.

Now, a new study from researchers at Wake Forest University School of Medicine shows that dopamine release in the human brain plays a crucial role in encoding both reward and punishment prediction errors. This means that dopamine is involved in the process of learning from both positive and negative experiences, allowing the brain to adjust and adapt its behavior based on the outcomes of these experiences.

The study was published today in Science Advances.

"Previously, research has shown that dopamine plays an important role in how animals learn from 'rewarding' (and possibly 'punishing') experiences. But, little work has been done to directly assess what dopamine does on fast timescales in the human brain," said Kenneth T. Kishida, Ph.D., associate professor of physiology and pharmacology and neurosurgery at Wake Forest University School of Medicine. "This is the first study in humans to examine how dopamine encodes rewards and punishments and whether dopamine reflects an 'optimal' teaching signal that is used in today's most advanced artificial intelligence research."

For the study, researchers on Kishida's team utilized fast-scan cyclic voltammetry, an electrochemical technique, paired with machine learning, to detect and measure dopamine levels in real-time (i.e., 10 measurements per second). However, this method is challenging and can only be performed during invasive procedures such as deep-brain stimulation (DBS) brain surgery. DBS is commonly employed to treat conditions such as Parkinson's disease, essential tremor, obsessive-compulsive disorder and epilepsy.

Kishida's team collaborated with Atrium Health Wake Forest Baptist neurosurgeons Stephen B. Tatter, M.D., and Adrian W. Laxton, M.D., who are also both faculty members in the Department of Neurosurgery at Wake Forest University School of Medicine, to insert a carbon fiber microelectrode deep into the brain of three participants at Atrium Health Wake Forest Baptist Medical Center who were scheduled to receive DBS to treat essential tremor.

While the participants were awake in the operating room, they played a simple computer game. As they played the game, dopamine measurements were taken in the striatum, a part of the brain that is important for cognition, decision-making, and coordinated movements.

During the game, participants' choices were either rewarded or punished with real monetary gains or losses. The game was divided into three stages in which participants learned from positive or negative feedback to make choices that maximized rewards and minimized penalties. Dopamine levels were measured continuously, once every 100 milliseconds, throughout each of the three stages of the game.

"We found that dopamine not only plays a role in signaling both positive and negative experiences in the brain, but it seems to do so in a way that is optimal when trying to learn from those outcomes. What was also interesting, is that it seems like there may be independent pathways in the brain that separately engage the dopamine system for rewarding versus punishing experiences. Our results reveal a surprising result that these two pathways may encode rewarding and punishing experiences on slightly shifted timescales separated by only 200 to 400 milliseconds in time," Kishida said.

Kishida believes that this level of understanding may lead to a better understanding of how the dopamine system is affected in humans with psychiatric and neurological disorders. Kishida said additional research is needed to understand how dopamine signaling is altered in psychiatric and neurological disorders.

"Traditionally, dopamine is often referred to as 'the pleasure neurotransmitter,"' Kishida said. "However, our work provides evidence that this is not the way to think about dopamine. Instead, dopamine is a crucial part of a sophisticated system that teaches our brain and guides our behavior. That dopamine is also involved in teaching our brain about punishing experiences is an important discovery and may provide new directions in research to help us better understand the mechanisms underlying depression, addiction, and related psychiatric and neurological disorders."

Read more at Science Daily

Meteorites likely source of nitrogen for early Earth

Micrometeorites originating from icy celestial bodies in the outer Solar System may be responsible for transporting nitrogen to the near-Earth region in the early days of our solar system. That discovery was published today in Nature Astronomy by an international team of researchers, including University of Hawai'i at Manoa scientists, led by Kyoto University.

Nitrogen compounds, such as ammonium salts, are abundant in material born in regions far from the sun, but evidence of their transport to Earth's orbital region had been poorly understood.

"Our recent findings suggests the possibility that a greater amount of nitrogen compounds than previously recognized was transported near Earth, potentially serving as building blocks for life on our planet," says Hope Ishii, study co-author and affiliate faculty at the Hawai'i Institute of Geophysics and Planetology in the UH Manoa School of Ocean and Earth Science and Technology (SOEST).

Like all asteroids, Ryugu is a small, rocky object that orbits the sun.

The Japan Aerospace Exploration Agency's Hayabusa2 spacecraft explored Ryugu and brought material from its surface back to Earth in 2020.

This intriguing asteroid is rich in carbon and has undergone significant space weathering caused by micrometeorite collisions and exposure to charged ions streaming from the sun.

In this study, the scientists aimed to discover clues about the materials arriving near Earth's orbit, where Ryugu is currently located, by examining the evidence of space weathering in Ryugu samples.

Using an electron microscope, they found that the surface of the Ryugu samples are covered with tiny minerals composed of iron and nitrogen (iron nitride: Fe4N).

"We proposed that tiny meteorites, called micrometeorites, containing ammonia compounds were delivered from icy celestial bodies and collided with Ryugu," said Toru Matsumoto, lead author of the study and assistant professor at Kyoto University.

"The micrometeorite collisions trigger chemical reactions on magnetite and lead to the formation of the iron nitride."

Read more at Science Daily

Small marine creatures swimming in plastic chemicals not reproducing

Plastic waste in the water might be stopping -- or interrupting -- some shrimp-like creatures from reproducing.

In a unique study, the ability of 'shrimp like' creatures to reproduce successfully was found to be compromised by chemicals found in everyday plastics.

Research showed that little critters, known as marine amphipod Echinogammarus marinus, changed their mating behaviour when exposed to toxic plastic additives.

Until now, most research into plastic pollution has focused on visual plastics; what can get trapped in plastics and the dangers of ingesting large particles.

Scientists from the University of Portsmouth have taken a different approach and investigated the chemicals that are used as ingredients in plastics.

Professor Alex Ford, from the Institute of Marine Sciences at the University of Portsmouth, says: "This unsuccessful mating behaviour has serious repercussions, not only for the species being tested but potentially for the population as a whole. These animals form pairs to reproduce. Once they were exposed to a chemical, they would break apart from their mate and take much longer -in some cases days -- to repair, and sometimes not at all.

"These creatures are commonly found on European shores, where they make up a substantial amount of the diet of fish and birds. If they are compromised it will have an effect on the whole food chain."

There are over 350,000 chemicals in use around the world in everyday products.

Ten thousand of these are used to enhance plastics. Chemicals can be used to make plastics more flexible, add colour, give sun protection or make plastic flameproof.

Around one third of these chemicals are known to be toxic to human's immune, nervous or reproductive systems.

The study, published in the journal Environmental Pollution, tested four widely used chemicals found in plastics.

These plastic additives are used in a variety of common products, for example, phthalates (DEHP and DBP) which are found in medical supplies, food packaging and toys.

Triphenyl phosphate (TPHP) is mainly used as a flame retardant in products like nail polish and electronic equipment, including cables, and N-butyl benzenesulfonamide (NBBS) is used in nylon, medical devices, cooking utensils and films.

Bidemi Green-Ojo, lead author and PhD Researcher in Environmental Toxicology at the University of Portsmouth, says: "We chose these four additives because the suspected danger they pose to human health is well documented. Two of the chemicals we investigated (DHP and DEHP) are regulated and not allowed to be used in products in Europe. The other two chemicals have no current restrictions on them and are found in many household products. We wanted to test the effects these chemicals had on aquatic mating behaviour."

The 'shrimp like' creatures which have been studied are known to pair up and typically lock together for two days while mating.

Pairs of them were exposed to each chemical, and researchers monitored their behaviour over four days, measuring the time it took for the creatures to mate.

They found that at best it took much longer for the creatures to re-pair, and at worst they didn't re-pair.

The experiment found that all the plastic additives had the capacity to reduce the overall percentage of animals that formed pairs.

The ones which did form pairs took longer to make contact and re-pair.

Two of the chemicals caused a concentration-dependent effect on shrimps' sperm, resulting in a decline of up to 60 per cent in sperm count of those exposed to elevated levels of the chemicals.

"Although the animals we tested were exposed to much higher concentrations than you would normally find in the environment, the results indicate these chemicals can affect sperm count," explains Professor Ford.

"It is conceivable that if we did the experiment on shrimps that had been exposed for a longer period or during critical stages in their life history, it would affect their sperm levels and quality."

Bidemi Green-Ojo adds: "We must understand more about these chemicals and how they affect behaviour. Many types of behaviour -- such as feeding, fight or flight mode, and reproduction -- are essential in an animal's life, and any abnormal behaviour may reduce the chances of survival.

Read more at Science Daily

What makes sustainable consumption so difficult

While many people want to achieve major long-term goals -- such as improving their diet, quitting smoking or adopting a more sustainable lifestyle -- they often find it difficult to do so. Is it all down to a lack of self-discipline? No, it's not, according to social psychologist Professor Wilhelm Hofmann from Ruhr University Bochum, Germany. For a review article in Nature Reviews Psychology, Hofmann has analyzed numerous research studies and highlighted the extent to which the physical and social environment influence individual behavior. He criticizes the fact that many psychological studies still tend to focus on the individual while ignoring crucial structural factors. The article was published online on November 20, 2023.

Environmental factors have enormous impact on decisions

Traditional approaches such as self-determination theory focus on personal autonomy.

This means that an individual's freedom of choice must be preserved at all costs.

"The public policy recommendations that result from this are to make no restrictions, provide sufficient information about the identified risks and side effects of the various options and then trust that people will make the right decisions and act appropriately," says Hofmann.

But this formula doesn't work.

To illustrate this, the Bochum-based psychologist cites the example of an eco-conscious consumer who'd like to reduce their meat consumption, but occasionally also finds themselves tempted by a meat dish.

"In conventional psychology, this is regarded as a conflict within the individual," he explains.

If the person could only muster enough willpower, they would achieve their long-term goal.

According to Hofmann, this view is misguided, because decisions are very much influenced by the environment: For example, if there are five meat dishes in the canteen, but only one vegetarian option -- and the latter might even be more expensive.

People also wish to conform to social norms: If many of your friends and relatives drive a big car, you're more likely to want one yourself.

It's not enough to hope for individual discipline

In his article, Hofmann combines psychological research with public policy research to illustrate that psychological research has implications for other areas and should take a broader view.

In particular, he argues that we need to be more aware of the fact that people don't have the power to shape many of their own environments.

"Many people try to live in a more sustainable manner, but fail to do so in reality," says Wilhelm Hofmann.

Unsustainable options are often cheaper, more visible and more available than sustainable ones.

"Relying on individual discipline, willingness to make sacrifices and a sense of guilt won't get us very far. We need to question and change the structures that contribute to social problems such as the overuse of natural resources and make sustainable behavior more difficult. And in order to achieve this, we need sound and effective political decisions." Many people would like to see more regulation so that they no longer have to swim against the tide.

Growing awareness of the problem, combined with the realization that some social challenges and crises can't be solved through personal responsibility or free markets, is driving the desire for government intervention and solutions.

In essence, society needs to agree on good rules in order to provide individuals with the best possible support on the path to the desired change towards greater sustainability.

Greater focus on the common good

"The accelerating climate crisis is the best example of how the unlimited exercise of personal consumer freedoms leads to negative consequences for society as a whole," explains Wilhelm Hofmann.

"We've forgotten to a certain extent to look at the collective benefit, i.e. the common good, and need to recognize the importance of good regulation once again. By this I mean that we need to agree on effective and fair rules that protect us from risks and that apply to everyone equally. Such as are standard practice in road traffic, for example."

Read more at Science Daily

One of the largest magnetic storms in history quantified: Aurorae covered much of the night sky from the Tropics to the Polar Regions

In early November of this year, aurora borealis were observed at surprisingly low latitudes, as far south as Italy and Texas. Such phenomena indicate the impacts of a solar coronal mass ejection on the Earth's magnetic field and atmosphere. Far more dramatic than this recent light show was, it was nothing compared to a huge solar storm in February 1872. The resulting auroral display from that event ringed the globe and produced auroras observed in sites as close to the equator as Bombay and Khartoum. An international team consisting of scientists from nine counties has now published a detailed study of this historically important event, tracing its solar origin and widespread terrestrial impacts. Telegraph communications were widely disrupted by this storm, but in today's technologically dependent society, such a storm would disrupt power grids and satellite communications. Their findings confirm that such extreme storms are more common than previously thought.

In the modern world, we are increasingly dependent on technological infrastructure such as power grids, communication systems, and satellites.

However, this dependency makes us increasingly vulnerable to the effects of large geomagnetic storms.

"The longer the power supply could be cut off, the more society, especially those living in urban areas, will struggle to cope," Designated Assistant Professor Hayakawa, the lead author of the study, explains.

Such storms could be big enough to knock out the power grid, communication systems, airplanes, and satellites in the worst case.

"Could we maintain our life without such infrastructure?" Hayakawa comments: "Well, let us just say that it would be extremely challenging."

Such extreme storms are rare. In recent studies, two such storms stand out: the Carrington storm in September 1859 and the New York Railroad storm in May 1921.

The new study suggests that another storm, the Chapman-Silverman storm in February 1872, should also be considered as one of these extreme events.

At the time, the storm was big enough to affect the technological infrastructure even in the tropics.

Telegraph communications on the submarine cable in the Indian Ocean between Bombay (Mumbai) and Aden were disrupted for hours.

Similar disturbances were reported on the land line between Cairo and Khartoum.

The multidisciplinary team, consisting of 22 scientists, was led by Nagoya University in Japan (Hisashi Hayakawa), the US National Solar Observatory (Edward Cliver), and the Royal Observatory of Belgium (Frédéric Clette). The 22 researchers used historical records and modern techniques to assess the Chapman-Silverman storm from its solar origin to its terrestrial impacts.

For the solar origin, the group turned to largely forgotten sunspot records from historical archives, especially Belgian and Italian records.

For terrestrial impacts, they used geomagnetic field measurements recorded in places as diverse as Bombay (Mumbai), Tiflis (Tbilisi), and Greenwich to assess temporal evolution and storm intensity.

They also examined hundreds of accounts of visual aurora in different languages caused by the storm.

One of the more interesting aspects of the 1872 storm was that it likely originated in a medium-sized, but complex, sunspot group near the solar disk centre as confirmed by analyses of solar records from Belgium and Italy.

These findings suggest that even a medium-sized sunspot group triggered one of the most extreme magnetic storms in history.

Hayakawa and his colleagues extended their investigations of the historical aurorae by combing through records in libraries, archives, and observatories around the world.

They identified more than 700 auroral records that indicated that the night sky was illuminated by magnificent auroral displays from the polar regions to the tropics (down to ≈ 20° in latitude in both hemispheres).

"Our findings confirm the Chapman-Silverman storm in February 1872 as one of the most extreme geomagnetic storms in recent history. Its size rivalled those of the Carrington storm in September 1859 and the NY Railroad storm in May 1921," Hayakawa said.

"This means that we now know that the world has seen at least three geomagnetic superstorms in the last two centuries. Space weather events that could cause such a major impact represent a risk that cannot be discounted."

Hayakawa said: "Such extreme events are rare. On the one hand, we are fortunate to have missed such superstorms in the modern time. On the other hand, the occurrence of three such superstorms in 6 decades shows that the threat to modern society is real. Therefore, the preservation and analysis of historical records is important to assess, understand, and mitigate the impact of such events."

Read more at Science Daily

An astronomical waltz reveals a sextuplet of planets

An international collaboration between astronomers using the CHEOPS and TESS space satellites, including NCCR PlanetS members from the University of Bern and the University of Geneva, have found a key new system of six transiting planets orbiting a bright star in a harmonic rhythm. This rare property enabled the team to determine the planetary orbits which initially appeared as an unsolvable riddle.

CHEOPS is a joint mission by ESA and Switzerland, under the leadership of the University of Bern in collaboration with the University of Geneva. Thanks to a collaboration with scientists working with data from NASA's satellite TESS, the international team could uncover the planetary system orbiting the nearby star HD110067. A very distinctive feature of this system is its chain of resonances: the planets orbit their host star in perfect harmony. Part of the research team are researchers from the University of Bern and the University of Geneva who are also members of the National Center of Competence in Research (NCCR) PlanetS. The findings have just been published in Nature.

The planets in the HD110067 system revolve around the star in a very precise waltz. When the closest planet to the star makes three full revolutions around it, the second one makes exactly two during the same time. This is called a 3:2 resonance. "Amongst the over 5000 exoplanets discovered orbiting other stars than our Sun, resonances are not rare, nor are systems with several planets. What is extremely rare though, is to find systems where the resonances span such a long chain of six planets" points out Dr. Hugh Osborn, CHEOPS fellow at the University of Bern, leader of CHEOPS observation programme involved in the study, and co-author of the publication. This is precisely the case of HD110067 whose planets form a so-called "resonant chain" in successive pairs of 3:2, 3:2, 3:2, 4:3, and 4:3 resonances, resulting in the closest planet completing six orbits while the outer-most planet does one.

A seemingly unsolvable puzzle

Although multiple planets were initially detected thanks to their transits, the exact arrangement of the planets was unclear at first. However, the precise gravitational dance enabled the scientists' team to solve the puzzle of HD110067. Prof. Adrien Leleu from the University of Geneva, in charge of analysing the orbital resonances, and co-author of the study, explains: "A transit occurs when a planet, from our point of view, passes in front of its host star, blocking a minute fraction of the starlight, creating an apparent dip of its brightness." From the first observations carried out by NASA's TESS satellite, it was possible to determine that the two inner planets called 'b' and 'c' have orbital periods of 9 and 14 days respectively. However, no conclusions could be drawn for the other four detected planets as two were seen to transit once in 2020 and once in 2022 with a large 2-year gap in the data, and the other two transited only once in 2022.

The solution to the puzzle for those four additional planets finally began to emerge thanks to observations with the CHEOPS space telescope. While TESS aims at scanning all of the sky bit by bit to find short-period exoplanets, CHEOPS is a targeted mission, focusing on a single star at a time with exquisite precision. "Our CHEOPS observations enabled us to find that the period of planet 'd' is 20.5 days. Also, it ruled out multiple possibilities for the remaining three outer planets, 'e', 'f' and 'g'," reveals Osborn.

Predicting the precise waltz of the planets

That is when the team realized that the three inner planets of HD110067 are dancing in a precise 3:2, 3:2 chain of resonances: when the innermost planet revolves nine times around the star, the second revolves six times and the third planet four times.

The team then considered the possibility that the three other planets could also be part of the chain of resonances. "This led to dozens of possibilities for their orbital period," explains Leleu, "but combining existing observational data from TESS and CHEOPS, with our model of the gravitational interactions between the planets, we could exclude all solutions but one: the 3:2, 3:2, 3:2, 4:3, 4:3 chain." The scientists could therefore predict that the outer three planets ('e', 'f' and 'g') have orbital periods of 31, 41 days, and 55 days.

This prediction allowed to schedule observations with a variety of ground-based telescopes. Further transits of planet 'f' were observed, revealing it was precisely where theory predicted it based on the resonant-chain. Finally, reanalysis of the data from TESS revealed two hidden transits, one from each of planets 'f' and 'g', exactly at the times expected by the predictions, confirming the periods of the six planets. Additional CHEOPS observations of each planet, and in particular planet 'e' are scheduled in the near future.

A key system for the future

From the handful of resonant-chain systems found so far, CHEOPS has highly contributed to the understanding of not only HD110067, but also of TOI-178. Another well-known example of a resonant-chain system is the TRAPPIST-1 system which hosts seven rocky planets. However, TRAPPIST-1 is a small and incredibly faint star which makes any additional observations very difficult. HD110067, on the other hand, is more than 50 times brighter than TRAPPIST-1.

Read more at Science Daily

Landscape dynamics determine the evolution of biodiversity on Earth

Movement of rivers, mountains, oceans and sediment nutrients at the geological timescale are the central drivers of Earth's biodiversity, new research published today in Nature has revealed.

The research also shows that biodiversity evolves at similar rates to the pace of plate tectonics, the slow geological processes that drive the shape of continents, mountains and oceans.

"That is a rate incomparably slower than the current rates of extinction caused by human activity," said lead author Dr Tristan Salles from the School of Geosciences.

The research looks back over 500 million years of Earth's history to the period just after the Cambrian explosion of life, which established the main species types of modern life.

Dr Salles said: "Earth's surface is the living skin of our planet. Over geological time, this surface evolves with rivers fragmenting the landscape into an environmentally diverse range of habitats.

"However, these rivers not only carve canyons and form valleys, but play the role of Earth's circulatory system as the main conduits for nutrient and sediment transfer from sources (mountains) to sinks (oceans).

"While modern science has a growing understanding of global biodiversity, we tend to view this through the prism of narrow expertise," Dr Salles said. "This is like looking inside a house from just one window and thinking we understand its architecture.

"Our model connects physical, chemical and biological systems over half a billion years in five-million-year chunks at a resolution of five kilometres. This gives an unprecedented understanding of what has driven the shape and timing of species diversity," he said.

The discovery in 1994 of the ancient Wollemi pine species in a secluded valley in the Blue Mountains west of Sydney gives us a glimpse into the holistic role that time, geology, hydrology, climate and genetics play in biodiversity and species survival.

The idea that landscapes play a role in the trajectory of life on Earth can be traced back to German naturalist and polymath Alexander von Humboldt. His work inspired Charles Darwin and Alfred Wallace, who were the first to note that animal species boundaries correspond to landscape discontinuities and gradients.

"Fast forwarding nearly 200 years, our understanding of how the diversity of marine and terrestrial life was assembled over the past 540 million years is still emerging," University of Sydney PhD student Beatriz Hadler Boggiani said.

"Biodiversity patterns are well identified from the fossil record and genetic studies. Yet, many aspects of this evolution remain enigmatic, such as the 100 million years delay between the expansion of plants on continents and the rapid diversification of marine life."

In groundbreaking research a team of scientists -- from the University of Sydney, ISTerre at the French state research organisation CNRS and the University of Grenoble Alpes in France -- has proposed a unified theory that connects the evolution of life in the marine and terrestrial realms to sediment pulses controlled by past landscapes.

"Because the evolution of the Earth's surface is set by the interplay between the geosphere and the atmosphere, it records their cumulative interactions and should, therefore, provide the context for biodiversity to evolve," said Dr Laurent Husson from University of Grenoble Alpes.

Instead of considering isolated pieces of the environmental puzzle independently, the team developed a model that combines them and simulates at high resolution the compounding effect of these forces.

"It is through calibration of this physical memory etched in the Earth's skin with genetics, fossils, climate, hydrology and tectonics by which we have investigated our hypothesis," Dr Salles said.

Using open-source scientific code published by the team in Science in March, the detailed simulation was calibrated using modern information about landscape elevations, erosion rates, major river waters and the geological transport of sediment (known as sediment flux).

This allowed the team to evaluate their predictions over 500 million years using a combination of geochemical proxies and testing different tectonic and climatic reconstructions. The geoscientists then compared the predicted sediment pulses to the evolution of life in both the marine and terrestrial realms obtained from a compilation of paleontological data.

"In a nutshell, we reconstructed Earth landforms over the Phanerozoic era, which started 540 million years ago, and looked at the correlations between the evolving river networks, sediment transfers and known distribution of marine and plant families," University of Grenoble PhD student Manon Lorcery said.

When comparing predicted sediment flux into the oceans with marine biodiversity, the analysis shows a strong, positive correlation.

On land, the authors designed a model integrating sediment cover and landscape variability to describe the capacity of the landscape to host diverse species. Here again, they found a striking correlation between their proxy and plant diversification for the past 450 million years.

In his 1864 novel A Journey to the Centre of the Earth, Jules Verne attributes this to his fictitious hero, Professor Otto Lidenbrock:

"Animal life existed upon the Earth only in the secondary period, when a sediment of soil had been deposited by the rivers and taken the place of the incandescent rocks of the primitive period."

Read more at Science Daily