Why does a leap year have 366 days?


You may be used to hearing that it takes the Earth 365 days to make a full lap, but that journey actually lasts about 365 and a quarter days. Leap years help to keep the 12-month calendar matched up with Earth’s movement around the Sun.

After four years, those leftover hours add up to a whole day. In a leap year, we add this extra day to the month of February, making it 29 days long instead of the usual 28.

The idea of an annual catch-up dates back to ancient Rome, where people had a calendar with 355 days instead of 365 because it was based on cycles and phases of the Moon. They noticed that their calendar was getting out of sync with the seasons, so they began adding an extra month, which they called Mercedonius, every two years to catch up with the missing days.

In the year 45 B.C.E., Roman emperor Julius Caesar introduced a solar calendar, based on one developed in Egypt. Every four years, February received an extra day to keep the calendar in line with the Earth’s journey around the Sun. In honor of Caesar, this system is still known as the Julian calendar.

But that wasn’t the last tweak. As time went on, people realized that the Earth’s journey wasn’t exactly 365.25 days – it actually took 365.24219 days, which is about 11 minutes less. So adding a whole day every four years was actually a little more correction than was needed.

In 1582, Pope Gregory XIII signed an order that made a small adjustment. There would still be a leap year every four years, except in “century” years – years divisible by 100, like 1700 or 2100 – unless they were also divisible by 400. It might sound a bit like a puzzle, but this adjustment made the calendar even more accurate – and from that point on, it was known as the Gregorian calendar.

What if we didn’t have leap years?

If the calendar didn’t make that small correction every four years, it would gradually fall out of alignment with the seasons. Over centuries, this could lead to the solstices and equinoxes occurring at different times than expected. Winter weather might develop in what the calendar showed as summer, and farmers could become confused about when to plant their seeds.

Without leap years, our calendar would gradually become disconnected from the seasons.

Other calendars around the world have their own ways of keeping time. The Jewish calendar, which is regulated by both the Moon and the Sun, is like a big puzzle with a 19-year cycle. Every now and then, it adds a leap month to make sure that special celebrations happen at just the right time.

The Islamic calendar is even more unusual. It follows the phases of the Moon and doesn’t add extra days. Since a lunar year is only about 355 days long, key dates on the Islamic calendar move 10 to 11 days earlier each year on the solar calendar.

For example, Ramadan, the Islamic month of fasting, falls in the ninth month of the Islamic calendar. In 2024, it will run from March 11 to April 9; in 2025, it will occur from March 1-29; and in 2026, it will be celebrated from Feb. 18 to March 19.

Learning from the planets

Astronomy originated as a way to make sense of our daily lives, linking the events around us to celestial phenomena. The concept of leap years exemplifies how, from early ages, humans found order in conditions that seemed chaotic.

Simple, unsophisticated but effective tools, born from creative ideas of ancient astronomers and visionaries, provided the first glimpses into understanding the nature that envelops us. Some ancient methods, such as astrometry and lists of astronomical objects, persist even today, revealing the timeless essence of our quest to understand nature.

Ancient Egyptians were dedicated astronomers. This section from the ceiling of the tomb of Senenmut, a high court official in Egypt, was drawn sometime circa 1479–1458 B.C.E. It shows constellations, protective gods and 24 segmented wheels for the hours of the day and the months of the year. NebMaatRa/Wikimedia, CC BY

People who do research in physics and astronomy, the field that I study, are inherently curious about the workings of the universe and our origins. This work is exciting, and also extremely humbling; it constantly shows that in the grand scheme, our lives occupy a mere second in the vast expanse of space and time – even in leap years when we add that extra day.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.The Conversation

Bhagya Subrayan, PhD Student in Physics and Astronomy, Purdue University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Researchers found 37 mine sites in Australia that could be converted into renewable energy storage. So what are we waiting for?

The world is rapidly moving towards a renewable energy future. To support the transition, we must prepare back-up energy supplies for times when solar panels and wind turbines are not producing enough electricity.

One solution is to build more pumped hydro energy storage. But where should this expansion happen?

Our new research identified more than 900 suitable locations around the world: at former and existing mining sites. Some 37 sites are in Australia.

Huge open-cut mining pits would be turned into reservoirs to hold water for renewable energy storage. It would give the sites a new lease on life and help shore up the world’s low-emissions future.

The benefits of pumped hydro storage

Pumped hydro energy storage has been demonstrated at scale for more than a century. Over the past few years, we have been identifying the best sites for “closed-loop” pumped hydro systems around the world.

Unlike conventional hydropower systems operating on rivers, closed-loop systems are located away from rivers. They require only two reservoirs, one higher than the other, between which water flows down a tunnel and through a turbine, producing electricity.

The water can be released – and power produced – to cover gaps in electricity supply when output from solar and wind is low (for example on cloudy or windless days). And when wind and solar are producing more electricity than is needed – such as on sunny or windy days – this cheap surplus power is used to pump the water back up the hill to the top reservoir, ready to be released again.

Off-river sites have very small environmental footprints and require very little water to operate. Pumped hydro energy storage is also generally cheaper than battery storage at large scales.

Batteries are the preferred method for energy storage over seconds to hours, while pumped hydro is preferred for overnight and longer storage.

Pumped-hydro storage technology has been demonstrated at scale for over a century. Shutterstock

Why mining sites?

There are big benefits to converting mining areas into pumped hydro plants.

For a start, the hole has already been dug, reducing construction costs. What’s more, mining sites are typically already serviced by roads and transmission infrastructure. The site usually has access to a water source for which the mine operators may have pumping rights. And the development takes place on land that is already cleared of vegetation, avoiding the need to disturb new areas.

Finally, community support may have already been obtained for the mining operations, which could easily be rolled over into a pumped hydro site.

In Australia, one pumped hydro energy storage project is already being built at a former gold mine site at Kidston in Far North Queensland.

The feasibility of two others is being assessed at Mount Rawdon near Bundaberg in Queensland, and at Muswellbrook in New South Wales. Both would repurpose old mining pits.

What we found

Our previous research identified suitable locations in undeveloped areas (excluding protected land) and using existing reservoirs. Now, we have turned our attention to mine sites.

Our study used a computer algorithm to search the Earth’s surface for suitable sites. It looked for mining pits, pit lakes and tailings ponds in mining sites which were located near suitable land for a new upper reservoir. The idea is that the reservoir and mining site are “paired” and water pumped between them.

Globally, we identified 904 suitable mining sites across 77 countries.

Some 37 suitable sites are located in Australia. They include the Mount Rawdon and Muswellbrook mining pits already under investigation.

There are a number of potential options in Western Australia: in the iron-ore region of the Pilbara, south of Perth and around Kalgoorlie.

Options in Queensland and New South Wales are mostly located down the east coast, including the Coppabella Mine and the coal mining pits near the old Liddell Power Station. Possible sites also exist inland at Mount Isa in Queensland and at the Cadia Hill gold mine near Orange in NSW.

Potential sites in South Australia include the old Leigh Creek coal mine in the Flinders Ranges and the operating Prominent Hill mine northwest of Adelaide. Tasmania and Victoria also offer possible locations, although many other non-mining options exist in these states for pumped hydro storage.

We are not suggesting that operating mines be closed – rather, that pumped hydro storage be considered as part of site rehabilitation at the end of the mine’s life.

If old mining sites are to be converted into pumped hydro, several challenges must be addressed. For example, mine pits may contain contaminants that, if filled with water, could seep into groundwater. However, this could be overcome by lining reservoirs.

Looking ahead

Australia has set a readily achievable goal of reaching 82% renewable electricity by 2030.

The Australian Energy Market Operator suggests by 2050, this nation needs about 640 gigawatt-hours of dispatchable or “on demand” storage to support solar and wind capacity. We currently have about 17 gigawatt-hours of electricity storage, with more committed by Snowy 2.0 and other projects.

The 37 possible pumped hydro sites we’ve identified could deliver 540 gigawatt-hours of storage potential. Combined with other non-mining sites we’ve identified previously, the options are far more numerous than our needs.

This means we can afford to be picky, and develop only the very best sites. So what are we waiting for?The Conversation

Timothy Weber, Research Officer for School of Engineering, Australian National University and Andrew Blakers, Professor of Engineering, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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The world is quietly losing the land it needs to feed itself

A drought-affected corn field in the town of Serodino, Santa Fe province, Argentina, on Thursday, Nov. 9, 2023. MUST CREDIT: Sebastian Lopez Brach/Bloomberg

The greatest threats to our existence today are caused by human activity rather than nature acting alone, according to a recent United Nations report.

Many people are familiar with human contribution to climate change and perhaps also the loss of biodiversity. But there’s a third environmental impact that rarely gets the attention it deserves: desertification, also known as land degradation.

The world is rapidly losing usable land for self-inflicted reasons, ranging from intensive agriculture and overgrazing of livestock to real estate development and, yes, climate change. The crisis is further fueling food and water insecurity, as well as adding to more greenhouse gas emissions.

Environmental scientists haven’t ignored the problem. In fact, the Earth Summit held in Rio de Janeiro in 1992 led to the creation of three UN conventions: climate change, biodiversity and desertification.

The climate convention holds big COP summits each year – such as COP28 in Dubai – that now frequently make front-page headlines.



But while the biodiversity and desertification conventions also hold COP summits, they’re only once every two years and rarely get that much interest. It’s a lost opportunity, says Ibrahim Thiaw, executive secretary of the UN Convention to Combat Desertification, who hinted it could be a branding issue because people think it’s only about deserts.

“There is a misunderstanding of the term desertification. That’s why we also use ‘land degradation,’” Thiaw said.

Ironically, one of the biggest challenges in the fight against land degradation is universal: We need to eat. About 40% of the planet’s land – 5 billion hectares – is used for farming. One third of that is to grow crops and the rest for grazing livestock.

Unfortunately, the world doesn’t have a great track record for sustainable agriculture practices. Over the past 500 years, human activity (mainly agriculture) has led to nearly 2 billion hectares of land being degraded.

That’s contributed to about 500 billion tons of carbon dioxide equivalent released from soil disturbance, or about a quarter of all greenhouse gases contributing to additional warming today. Further land degradation until 2050 could add another 120 billion tons of carbon dioxide equivalent to the atmosphere, worsening climate change.

Thiaw said focusing attention on land restoration projects could flip this script. “There are no solutions for land degradation that also don’t have benefits for other problems we face,” he said.

Along with curbing emissions, a World Economic Forum report found that investing about $2.7 trillion each year in ecosystem restoration, regenerative agriculture and circular business models could help add nearly 400 million new jobs and generate more than $10 trillion in economic value annually.

Governments globally spend more than $600 billion on direct agricultural subsidies that can be redirected toward practices that help land restoration and increase yields, said Thiaw. “There’s nothing more irrational than taking public money to destroy your own natural capital,” he said. “But it is being done election after election.”

One reason why the problem of land degradation has been largely ignored might be that humans have lost their link to the land, according to Osama Ibrahim Faqeeha, deputy minister for environment in Saudi Arabia, which will host COP16 on desertification later this year.

“A big portion of the population lives in cities now. We live in a concrete forest,” Faqeeha said. “So few people have a direct connection between us and food production.”

Another explanation might have to do with how rich countries treated the problem. “For the longest time it was considered an African issue” by developed countries, said Thiaw. “It was not seen as a global issue.” Today land degradation and drought affect almost every country in the world.

Even the biggest economy in the world isn’t able to ignore land degradation. “When you think about soil, the US Secretary of State is probably not the first person who comes to mind,” said Antony Blinken at this year’s World Economic Forum in Davos. “But the truth is soil is literally at the root of many pressing national security challenges we face.”

Global demand for food is expected to increase 50% by 2050, said Blinken, even as climate change could reduce global yields by 30%. “A parent who can’t put food on the table for their children picks up the family and moves,” he said, “And if that means moving halfway around the world, they will. But that contributes to unprecedented migration flows.”

– – –Akshat Rathi writes the Zero newsletter, which examines the world’s race to cut planet-warming emissions. His book Climate Capitalism will be published in the US and Canada on March 12.The world is quietly losing the land it needs to feed itself
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Scientists shocked to discover new species of green anaconda, the world’s biggest snake

The green anaconda has long been considered one of the Amazon’s most formidable and mysterious animals. Our new research upends scientific understanding of this magnificent creature, revealing it is actually two genetically different species. The surprising finding opens a new chapter in conservation of this top jungle predator.

Green anacondas are the world’s heaviest snakes, and among the longest. Predominantly found in rivers and wetlands in South America, they are renowned for their lightning speed and ability to asphyxiate huge prey then swallow them whole.

My colleagues and I were shocked to discover significant genetic differences between the two anaconda species. Given the reptile is such a large vertebrate, it’s remarkable this difference has slipped under the radar until now.

Conservation strategies for green anacondas must now be reassessed, to help each unique species cope with threats such as climate change, habitat degradation and pollution. The findings also show the urgent need to better understand the diversity of Earth’s animal and plant species before it’s too late.

Scientists discovered a new snake species known as the northern green anaconda. Bryan Fry

An impressive apex predator

Historically, four anaconda species have been recognised, including green anacondas (also known as giant anacondas).

Green anacondas are true behemoths of the reptile world. The largest females can grow to more than seven metres long and weigh more than 250 kilograms.

The snakes are well-adapted to a life lived mostly in water. Their nostrils and eyes are on top of their head, so they can see and breathe while the rest of their body is submerged. Anacondas are olive-coloured with large black spots, enabling them to blend in with their surroundings.

The snakes inhabit the lush, intricate waterways of South America’s Amazon and Orinoco basins. They are known for their stealth, patience and surprising agility. The buoyancy of the water supports the animal’s substantial bulk and enables it to move easily and leap out to ambush prey as large as capybaras (giant rodents), caimans (reptiles from the alligator family) and deer.

Green anacondas are not venomous. Instead they take down prey using their large, flexible jaws then crush it with their strong bodies, before swallowing it.

As apex predators, green anacondas are vital to maintaining balance in their ecosystems. This role extends beyond their hunting. Their very presence alters the behaviour of a wide range of other species, influencing where and how they forage, breed and migrate.

Anacondas are highly sensitive to environmental change. Healthy anaconda populations indicate healthy, vibrant ecosystems, with ample food resources and clean water. Declining anaconda numbers may be harbingers of environmental distress. So knowing which anaconda species exist, and monitoring their numbers, is crucial.

To date, there has been little research into genetic differences between anaconda species. Our research aimed to close that knowledge gap.

Green anaconda have large, flexible jaws. Pictured: a green anaconda eating a deer. JESUS RIVAS

Untangling anaconda genes

We studied representative samples from all anaconda species throughout their distribution, across nine countries.

Our project spanned almost 20 years. Crucial pieces of the puzzle came from samples we collected on a 2022 expedition to the Bameno region of Baihuaeri Waorani Territory in the Ecuadorian Amazon. We took this trip at the invitation of, and in collaboration with, Waorani leader Penti Baihua. Actor Will Smith also joined the expedition, as part of a series he is filming for National Geographic.

We surveyed anacondas from various locations throughout their ranges in South America. Conditions were difficult. We paddled up muddy rivers and slogged through swamps. The heat was relentless and swarms of insects were omnipresent.

We collected data such as habitat type and location, and rainfall patterns. We also collected tissue and/or blood from each specimen and analysed them back in the lab. This revealed the green anaconda, formerly believed to be a single species, is actually two genetically distinct species.

The first is the known species, Eunectes murinus, which lives in Perú, Bolivia, French Guiana and Brazil. We have given it the common name “southern green anaconda”. The second, newly identified species is Eunectes akayima or “northern green anaconda”, which is found in Ecuador, Colombia, Venezuela, Trinidad, Guyana, Suriname and French Guiana.

We also identified the period in time where the green anaconda diverged into two species: almost 10 million years ago.

The two species of green anaconda look almost identical, and no obvious geographical barrier exists to separate them. But their level of genetic divergence – 5.5% – is staggering. By comparison, the genetic difference between humans and apes is about 2%.

The two green anaconda species live much of their lives in water. Shutterstock

Preserving the web of life

Our research has peeled back a layer of the mystery surrounding green anacondas. This discovery has significant implications for the conservation of these species – particularly for the newly identified northern green anaconda.

Until now, the two species have been managed as a single entity. But each may have different ecological niches and ranges, and face different threats.

Tailored conservation strategies must be devised to safeguard the future of both species. This may include new legal protections and initiatives to protect habitat. It may also involve measures to mitigate the harm caused by climate change, deforestation and pollution — such as devastating effects of oil spills on aquatic habitats.

Our research is also a reminder of the complexities involved in biodiversity conservation. When species go unrecognised, they can slip through the cracks of conservation programs. By incorporating genetic taxonomy into conservation planning, we can better preserve Earth’s intricate web of life – both the species we know today, and those yet to be discovered.The Conversation

Bryan G. Fry, Professor of Toxicology, School of the Environment, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Indian American scientist hoping to be first woman to jump from stratosphere

Swati Varshey has a PhD in materials science from the Massachusetts Institute of Technology and has made over 1,200 jumps with a speciality in vertical freefall, according to Space.com. Swati Varshney. PHOTO: @risingunited.org An Indian-American scientist is hoping to become the first woman to skydive from the stratosphere at an altitude of 42.5 km above the Earth, and shatter four records in the process. Swati Varshey has been selected as one of the three candidates selected by the Hera Project of Rising United that seeks to empower women in science and technology, the organization has announced. - If she makes it to the skydive in 2025, Hera Project expects her to break four current records: The free fall record by 1.1 kilometer from the highest altitude; endure the longest free fall time; break the sound barrier unaided by 264 kph; and the highest crewed balloon flight by over 1 kilometer. “At Rising United, we’re embarking on a historic journey, shattering records and ceilings to advance women’s equality and inspire young women’s interest in STEAM education”, the organization said. Swati Varshey has a PhD in materials science from the Massachusetts Institute of Technology and has made over 1,200 jumps with a specialty in vertical freefall, according to Space.com. Billed as the “First Female Mission to the Edge of Space”, the project seeks to have minority women smash the records, and the other two contenders are of Latino descent, Eliana Rodriquez and Diana Valerín Jiménez. The project will include educational programs for schools to increase interest in science and technology among girls, especially from minority groups. Varshney told Space.com that for her skydiving “is a lot more similar to my scientific training than I ever thought it would have been in the first place. It was just another avenue for me to pursue this goal of lifelong learning”. Varshney, who has spent a decade skydiving, told the media outlet, “My academic progression and my career trajectory has been really intertwined with skydiving as it went along. So I started skydiving”. She tried tandem jumping and found it such a “blast”, that she took it up as a hobby. “ I really just wanted something that was totally different, and as a release to — this is a really cliché way to say it — cut away right from what I was doing in my day-to-day life”, she told Space.com. “It became this never-ending journey of another pursuit of knowledge that went alongside my academic career”, she added. The stratosphere is from about 6 kilometers to 50 kilometers above the earth where it gives way to the mesosphere. Indian American scientist hoping to be first woman to jump from stratosphere:
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