Historical geography helps researchers solve 2,700-year old eclipse mystery

Humanity’s earliest datable record for a total solar eclipse allows scientists to derive accurate measurements of Earth’s ancient rotation speed and provides independent validation of solar cycle reconstruction in the 8th century BCE

Nagoya University

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image: 

Artist's interpretation of an ancient total solar eclipse. This illustration is based on artistic imagination and does not represent the exact appearance of the eclipse recorded in 709 BCE. 

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Credit: Kano Okada, Nagoya University (Based on an image by Phil Hart: https://apod.nasa.gov/apod/ap240402.html)

An international team of researchers has used knowledge of historical geography to reexamine the earliest datable total solar eclipse record known to the scientific community, enabling accurate measurements of Earth's variable rotation speed from 709 BCE. The researchers calculated how the Sun would have appeared from Qufu, the ancient Chinese capital of the Lu Duchy, during the total solar eclipse. Using this information, they analyzed the ancient description of what has been considered the solar corona—the dim outer atmosphere of the Sun visible to the naked eye only during total eclipses—and found that its morphology supports recent solar cycle reconstructions for the 8th century BCE. 

Their findings, published in Astrophysical Journal Letters, provide reliable new data about Earth's rotation speed during this period and suggest the Sun was becoming more active after a long quiet period, independently confirming what other scientists have found using radiocarbon analysis. 
 

Finding the true location of an ancient capital 

The total solar eclipse occurred on 17 July 709 BCE and was reported from Lu Duchy Court. Its description was found in a chronicle titled the “Spring and Autumn Annals” that was compiled roughly 2-3 centuries after the eclipse. The event was recorded as “the Sun was totally eclipsed.”  

“What makes this record special isn’t just its age, but also a later addendum in the ‘Hanshu’ (Book of Han) based on a quote written seven centuries after the eclipse. It describes the eclipsed Sun as ‘completely yellow above and below.’ This addendum has been traditionally associated with a record of a solar corona. If this is truly the case, it represents one of the earliest surviving written descriptions of the solar corona,” lead author Hisashi Hayakawa, Assistant Professor from the Institute for Space-Earth Environmental Research and Institute for Advanced Research at Nagoya University explained. 

When the researchers tried to verify the solar eclipse record using modern astronomical calculations and reconstructions of Earth’s rotation speed, they found that a total eclipse would not have been visible from the Lu Court at Qufu. They realized earlier studies had missed the exact location of the ancient city. 

To correct the coordinates of ancient Qufu the researchers used knowledge of historical geography, consulting archaeological excavation reports of the ancient city. They found that previous studies used coordinates that were some eight kilometers away from the true location.  

"This correction allowed us to accurately measure the Earth's rotation during the total eclipse, calculate the orientation of the Sun’s rotation axis, and simulate the corona’s appearance," explained Hayakawa, who holds PhDs in both solar physics and oriental history. 

China developed exceptional traditions for astronomical records because ancient dynasties hired experts to monitor celestial events for omenological reasons—the practice of interpreting celestial events as omens or signs. They believed strange sky phenomena indicated political wrongdoing by emperors, which motivated careful tracking of eclipses, auroras, and other astronomical events. Consequently, this systematic record-keeping across multiple dynasties has given China some of the world’s best ancient eclipse records. 

While the 709 BCE event represents the earliest explicit written mention of a total solar eclipse and possibly the earliest surviving description that refers to a solar corona, Hayakawa and his colleagues raise caveats on the reliability of the corona description because it appears only in the Hanshu as a quote written some seven centuries after the event. Although questions remain about the reliability of the later corona description, the eclipse timing itself is based on scientific consensus and provides reliable new information on Earth’s rotation and potential independent support for recent solar cycle studies. 

 

When Earth spun faster and the Sun was quieter 

Our planet spins slightly slower now than it did 2,700 years ago because of several factors including friction from ocean tides caused by the Moon’s gravity. Using the corrected coordinates, the team derived new accurate measurements of Earth’s rotation speed in the 8th to 6th centuries BCE.  

The study revealed that delta T (ΔT), a parameter for the Earth’s rotation speed variability, during this eclipse was between 20,264 and 21,204 seconds. “This new dataset fixes coordinate errors in previous Earth rotation studies. Additionally, it improves the accuracy of dating and reconstructing historical astronomical events,” Mitsuru Sôma, coauthor from the National Astronomical Observatory of Japan said. 

The research also supports recent solar cycle studies based on radiocarbon data from tree rings. “This unique historical addendum for the possible solar coronal structure is critical for providing a spot reference on solar activity reconstructions from tree rings and ice cores, as well as providing independent validation of solar activity models,” Mathew Owens, coauthor and professor of Space Physics at the University of Reading explained.  

During photosynthesis, trees absorb carbon, including radiocarbon, which is stored in their annual growth rings. Because radiocarbon concentrations reflect past cosmic ray levels and cosmic rays decrease when solar activity increases, scientists measure these concentrations to track solar activity over time and reconstruct past solar cycles.  

Approximately every 11 years the Sun cycles between more-active and less-active phases. Sometimes this pattern is interrupted by longer quiet periods called “grand minima” when the Sun produces only stray sunspots. The eclipse occurred just after the end of a period of decreased solar activity known as the “Neo Assyrian Grand Minimum” or “Homer Grand Minimum,” lasting from 808 to 717 BCE.  

Morphologically, the ancient observers' descriptions of the probable coronal structure suggest the Sun had come back to regular solar cycles with substantial magnetic activity by 709 BCE and reached the peak of its 11-year cycle. This result supports what other scientists have reconstructed using tree ring data. 

This interdisciplinary study demonstrates how ancient human observations continue to provide invaluable scientific data. “Some of our ancestors were very skilled observers,” Dr. Meng Jin, coauthor from the Lockheed Martin Solar and Astrophysics Laboratory, noted. “When we combine their careful records with modern computational methods and historical evidence, we can potentially find new information about our planet and our star from thousands of years ago.”  

Ancient Chinese text from the Spring and Autumn Annals that contains humanity’s earliest datable written record of a total solar eclipse from 709 BCE. The text states “In autumn, in the seventh month, on the renchen day, the first day of the month, the Sun was totally eclipsed.” The term “renchen” refers to a specific day in the traditional Chinese 60-day calendar cycle.

Later Chinese historical text from the “Hanshu” (Book of Han), an official dynastic history, providing additional details about the 709 BCE eclipse. This source includes the description that the eclipsed Sun appeared “completely yellow above and below,” which scientists regard as a description of the solar corona.

Credit

Image courtesy of the National Archives of Japan

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Journal

The Astrophysical Journal Letters

DOI

10.3847/2041-8213/ae0461 

Method of Research

Computational simulation/modeling

Subject of Research

Not applicable

Article Title

Analyses of the Ancient Chinese Report on the Total Solar Eclipse in 709 BCE: Implications for the Contemporaneous Earth’s Rotation Speed and Solar Cycles

Article Publication Date

2-Dec-2025

 

Seashells offer low-carbon concrete breakthrough in new study

New research from the University of East London reveals sustainable cement alternative from shoreline waste

University of East London

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A team of researchers from the University of East London (UEL) has found an unexpected solution to one of the construction industry’s biggest carbon problems - and it lies on the shoreline. New findings show that discarded seashells, typically treated as waste, can be transformed into a low-carbon concrete ingredient, potentially cutting significant amounts of CO₂ from one of the world’s most polluting materials and helping drive more sustainable construction.

The research offers a novel route to cutting the environmental burden of cement, which is responsible for around 7 per cent of global carbon emissions. By grinding discarded scallop-shells into fine powders and substituting them for part of the cement mix, the team achieved carbon reductions of up to 36 per cent - while keeping most of the concrete’s core performance features intact.

The study - Experimental Investigation of Low Carbon Concrete Using Ground Seashell Powder as Filler and Partial Cement Replacement - demonstrates that shells, once processed into two fine powder grades, can act as both a filler and a partial cement substitute.

Dr Ali Abass, Associate Professor of Structural Engineering at UEL and study lead, said the findings highlight a promising opportunity for industry,

“Concrete is everywhere, and consequently its carbon footprint is enormous. What we’ve shown is that something as ordinary as discarded shells can make a meaningful dent in those emissions. At moderate replacement levels the concrete behaves very well, which means this could be scaled up in real-world settings.”

The team’s microstructural analysis revealed that the calcium-rich shells help refine the pore structure of the concrete and support the formation of additional binding compounds, offering further performance benefits.

“Millions of tonnes of shell waste are produced globally each year, and most of it has no useful destination,” Dr Abass added. “If we can divert even a fraction of that into low-carbon construction materials, the environmental gains could be significant. It’s a simple idea with real potential to reshape part of the sector.”

The potential for adoption across the construction sector is considerable, particularly as tighter environmental standards and whole-life carbon reporting become more prevalent. With infrastructure and building contractors under growing pressure to decarbonise supply chains, the use of naturally derived waste materials could offer an accessible route to measurable reductions.

If further industry trials confirm the material’s reliability at scale, shell-derived concrete could support a shift towards more circular economic models, in which waste streams from one industry feed directly into another.

The research was first published in Construction Materials, an open-access journal from MDPI.

As Dr Abass added, “A future where yesterday’s coastal by-product becomes tomorrow’s structural backbone isn’t far-fetched - it’s practical, cost-effective, and increasingly necessary.”

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Journal

Construction Materials

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Experimental Investigation of Low Carbon Concrete Using Ground Seashell Powder as Filler and Partial Cement Replacement

 

Epigenetics linked to high-altitude adaptation in Andes

Whole methylome data gives new insights into Indigenous people of South America

Emory University

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DNA sequencing technology makes it possible to explore the genome to learn how humans adapted to live in a wide range of environments. Research has shown, for instance, that Tibetans living at high altitude in the Himalayas have a unique variant of a gene that expands the oxygen-carrying capacity of their blood.

Scientists, however, have not found a strong signal for this “high-altitude gene” in the genomes of Indigenous people living in the Andes Mountains of South America. It’s been less clear how people adapted to the altitudes greater than 2,500 meters in the Andean highlands, where low-oxygen levels, frigid temperatures and intense ultraviolet radiation make life challenging in the extreme.

A study led by anthropologists at Emory University took a new approach to explore this Andean mystery.

Rather than scan the whole genome of Indigenous people to look for alterations in the genetic code, the researchers scanned the entire methylome. The methylome reveals what are called “epigenetic” changes in the genome — how genes are expressed in response to the environment through a chemical process known as DNA methylation.

The journal Environmental Epigenetics published the research, which adds to the evidence that epigenetics may play a bigger role in adaptation than previously realized.

The researchers compared the methylomes of 39 individuals from two modern-day Indigenous populations: the Kichwa from the Andean highlands of Ecuador and the Ashaninka from the lowland Amazon Basin along the Peruvian border of Ecuador.

“This is the first whole methylome data on these two populations,” says Yemko Pryor, first author of the study, who led the project as an Emory PhD student. “Unlike many methylome studies that focus on just a few hundred thousand sites throughout the genome, we looked at all three million base pairs to see what we would find.”

The results identified strong differences in DNA methylation between the low- and high-altitude populations for the PSMA8 gene, associated with regulation of the vascular system, and for the FST gene, associated with regulating muscles in the heart. 

The second strongest signal detected in the high-altitude population compared to the low-altitude population was for genes within the P13K/AKT pathway, which is associated with muscle growth and the creation of new blood vessels.

The researchers hypothesize that the interplay between these epigenetic differences may help explain the increased muscularization of small arteries and higher blood viscosity that has been found in high-altitude Andean populations. These differences, they explain, may represent a unique vascular adaptation to a low-oxygen environment distinct from those found in Tibetan populations.

And the researchers note that the P13K/AKT pathway has been implicated in arteriole wall thickening under low-oxygen conditions in rats, as well as in human cells. “Arteriole wall thickening in humans has been linked to the development of pulmonary hypertension, which is more common in Andean highlanders compared to other highland populations,” they write.

The current study also identified strong differences between the two populations in the methylation of 39 pigmentation-related genes, which may help explain adaptation by the high-altitude population to strong ultraviolet radiation.

“The findings are particularly interesting because we’re not seeing these strong signals in the genome but when we look at the methylome, we are seeing these changes,” says John Lindo, Emory associate professor of anthropology and senior author of the study.

Gene selection theory holds that a gene that helps a population to adapt over time needs to be reliably inherited and therefore would show up in the genetic code of the genome. An epigenetic change, however, represents a more flexible response to an environmental influence, which would not necessarily be passed down to offspring.

“The Kichwa population that participated in our study did not just arrive in the Andean highlands — their ancestors had been living there for nearly 10,000 years,” Lindo says. “Our findings suggest that epigenetics can contribute to adaptation in a longstanding way.”

Co-authors of the current paper include scientists from Central University of Ecuador; the Institute of Medicine and Forensic Sciences in Lima, Peru; the State University of Rio de Janeiro; and the University of Pavia in Pavia, Italy.

Lindo established the Lindo Ancient DNA Laboratory at Emory in 2020. The state-of-the-art facility is one of the handful of ancient DNA labs in the country and one of the few in the world involved in every step of the complex process of solving mysteries surround ancient remains. A focus of the lab is exploring how environmental changes — including those caused by European contact — affected the biology of Indigenous and other populations of the Americas.

“I was one of the first graduate students to join the lab,” says Pryor, who received her PhD from Emory in June. “I learned how to build a lab from the ground up while also getting hands-on analytical and technical skills.”

While much of the lab’s work centers on ancient DNA, it also spans analyses of modern-day Indigenous populations, both for comparative studies and to fill in gaps around key questions when ancient samples are lacking.

The Emory lab builds relationships with Indigenous populations and local scientists, establishing full collaborations to conduct the research and ensuring that the participating communities have access to the findings.

As part of her Emory experience, Pryor traveled to Ecuador to meet with local archaeologists and members of Indigenous communities participating in some of the lab’s research projects.

“As a scientist doing research on humans, it’s also important to go beyond the data and be in community with people,” she says. “As much as I love doing analyses in the lab, it was a beautiful experience for me to get to go into the field and engage directly with people there.”

A key component of the current paper will be workshops that the team will hold to convey their findings directly to the Kichwa and Ashaninka communities. Co-author Daniel Rivas Alava, an Emory graduate student of anthropology and a native of Ecuador, is currently developing the Kichwa workshop.

Pryor graduated from Emory in June and is now a postdoctoral fellow in the lab of Tina Lasisi at the University of Michigan, researching the evolution and genetic basis of variation in human characteristics, with a focus on pigmentation and hair.

“I’m applying many of the techniques I learned at Emory, especially computational skills,” Pryor says. “My dream is to stay in academia and start my own ancient DNA lab one day.”

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Journal

Environmental Epigenetics

DOI

10.1093/eep/dvaf026 

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

Whole methylomes reveal high-altitude-associated methlation at hypoxia and pigmentation genes in South American Indigenous populations

Language mixing has no negative effect on toddlers’ vocabulary development, Concordia research shows

Parents in bilingual families often switch languages when talking to young children, for a variety of reasons

Concordia University

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Krista Byers-Heinlein, left, and Alexandra Paquette

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Credit: Concordia University

Parents in bilingual and multilingual families can wrestle with when and how to expose infants and toddlers to words in different languages. However, a new paper from the Concordia Infant Research Lab shows that language mixing does not harm a child’s ability to learn words.

In fact, switching languages, even mid-sentence or to introduce a single word, is considered both a common and flexible way to communicate in multilingual homes.

“We found that language mixing is often an intentional strategy rather than something parents do subconsciously,” says PhD student Alexandra Paquette, the study’s lead author. “There was no strong evidence that vocabulary size was tied to language mixing. We found that children were able to successfully navigate two languages, even when they appeared in the same sentence. Parents don’t need to worry that mixing harms their child’s ability to learn new words.”

Franglais begins at home

The study, published in the journal Behavioral Sciences, looks at data from almost 400 Montreal children being raised in bilingual homes. The Canadian metropolis benefits from a linguistically diverse population. French and English are both societal languages, meaning large portions of the population speak one or both. The city’s linguistic makeup is also enriched by its significant immigrant population, who speak multiple heritage languages. The most common are Spanish, Arabic and Italian.

The researchers analyzed two groups: French-English bilingual families and families who speak a heritage language along with English and/or French. Parents completed detailed questionnaires about how often they mixed languages, their reasons for doing so and how much of each language their child heard. They also documented their children’s understanding and use of words.

The results show that language mixing is common, but its frequency varies depending on the family’s linguistic background. French-English parents tended to mix less than heritage-language parents, likely because both societal languages are well supported in Montreal. Heritage-language parents mixed more often, especially borrowing English or French terms while speaking their heritage language.

Parents of all backgrounds said they switched languages for several reasons: they could not find the right word in English, French or their heritage language; no good translation was available; or they wanted to introduce a new word to their child. Parents in French-English families with older toddlers were more likely to deliberately mix languages to encourage language development.

The researchers point out that language mixing had almost no effect on a child’s vocabulary score in either French-English or English- or French-heritage language families. Even if parents mixed often, children knew the same number of words.

A unique linguistic environment

Montreal’s particular makeup as a city with two status languages supplemented by many heritage languages shapes how parents raise their bilingual children. Language mixing is a byproduct of a cultural context in which language mixing is common in daily life in both English and French communities.

“This project shows us how flexible children when it comes to language development,” says co-author Krista Byers-Heinlein, a professor in the Department of Psychology.

“Rather than confuse children, language mixing can be a real teaching tool that parents have in their toolbox. Parents are strategic about it, and our research finds that it is either neutral or beneficial when it comes to vocabulary.”

Read the cited paper: “Parental Language Mixing in Montreal: Rates, Predictors, and Relation to Infants’ Vocabulary Size”

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Journal

Behavioral Science

DOI

10.3390/bs15101371 

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

Parental Language Mixing in Montreal: Rates, Predictors, and Relation to Infants’ Vocabulary Size