What can my blinking tell me about my health?
Why does a leap year have 366 days?
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.
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.
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.
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.
The world is quietly losing the land it needs to feed itself
Think you’re good at multi-tasking? Here’s how your brain compensates – and how this changes with age
Arlington Research/Unsplash Peter Wilson, Australian Catholic UniversityWe’re all time-poor, so multi-tasking is seen as a necessity of modern living. We answer work emails while watching TV, make shopping lists in meetings and listen to podcasts when doing the dishes. We attempt to split our attention countless times a day when juggling both mundane and important tasks.
But doing two things at the same time isn’t always as productive or safe as focusing on one thing at a time.
The dilemma with multi-tasking is that when tasks become complex or energy-demanding, like driving a car while talking on the phone, our performance often drops on one or both.
Here’s why – and how our ability to multi-task changes as we age.
Doing more things, but less effectively
The issue with multi-tasking at a brain level, is that two tasks performed at the same time often compete for common neural pathways – like two intersecting streams of traffic on a road.
In particular, the brain’s planning centres in the frontal cortex (and connections to parieto-cerebellar system, among others) are needed for both motor and cognitive tasks. The more tasks rely on the same sensory system, like vision, the greater the interference.
This is why multi-tasking, such as talking on the phone, while driving can be risky. It takes longer to react to critical events, such as a car braking suddenly, and you have a higher risk of missing critical signals, such as a red light.
The more involved the phone conversation, the higher the accident risk, even when talking “hands-free”.
Generally, the more skilled you are on a primary motor task, the better able you are to juggle another task at the same time. Skilled surgeons, for example, can multitask more effectively than residents, which is reassuring in a busy operating suite.
Highly automated skills and efficient brain processes mean greater flexibility when multi-tasking.
Adults are better at multi-tasking than kids
Both brain capacity and experience endow adults with a greater capacity for multi-tasking compared with children.
You may have noticed that when you start thinking about a problem, you walk more slowly, and sometimes to a standstill if deep in thought. The ability to walk and think at the same time gets better over childhood and adolescence, as do other types of multi-tasking.
When children do these two things at once, their walking speed and smoothness both wane, particularly when also doing a memory task (like recalling a sequence of numbers), verbal fluency task (like naming animals) or a fine-motor task (like buttoning up a shirt). Alternately, outside the lab, the cognitive task might fall by wayside as the motor goal takes precedence.
Brain maturation has a lot to do with these age differences. A larger prefrontal cortex helps share cognitive resources between tasks, thereby reducing the costs. This means better capacity to maintain performance at or near single-task levels.
The white matter tract that connects our two hemispheres (the corpus callosum) also takes a long time to fully mature, placing limits on how well children can walk around and do manual tasks (like texting on a phone) together.
For a child or adult with motor skill difficulties, or developmental coordination disorder, multi-tastking errors are more common. Simply standing still while solving a visual task (like judging which of two lines is longer) is hard. When walking, it takes much longer to complete a path if it also involves cognitive effort along the way. So you can imagine how difficult walking to school could be.
What about as we approach older age?
Older adults are more prone to multi-tasking errors. When walking, for example, adding another task generally means older adults walk much slower and with less fluid movement than younger adults.
These age differences are even more pronounced when obstacles must be avoided or the path is winding or uneven.
Older adults tend to enlist more of their prefrontal cortex when walking and, especially, when multi-tasking. This creates more interference when the same brain networks are also enlisted to perform a cognitive task.
These age differences in performance of multi-tasking might be more “compensatory” than anything else, allowing older adults more time and safety when negotiating events around them.
Older people can practise and improve
Testing multi-tasking capabilities can tell clinicians about an older patient’s risk of future falls better than an assessment of walking alone, even for healthy people living in the community.
Testing can be as simple as asking someone to walk a path while either mentally subtracting by sevens, carrying a cup and saucer, or balancing a ball on a tray.
Patients can then practise and improve these abilities by, for example, pedalling an exercise bike or walking on a treadmill while composing a poem, making a shopping list, or playing a word game.
The goal is for patients to be able to divide their attention more efficiently across two tasks and to ignore distractions, improving speed and balance.
There are times when we do think better when moving
Let’s not forget that a good walk can help unclutter our mind and promote creative thought. And, some research shows walking can improve our ability to search and respond to visual events in the environment.
But often, it’s better to focus on one thing at a time
We often overlook the emotional and energy costs of multi-tasking when time-pressured. In many areas of life – home, work and school – we think it will save us time and energy. But the reality can be different.
Multi-tasking can sometimes sap our reserves and create stress, raising our cortisol levels, especially when we’re time-pressured. If such performance is sustained over long periods, it can leave you feeling fatigued or just plain empty.
Deep thinking is energy demanding by itself and so caution is sometimes warranted when acting at the same time – such as being immersed in deep thought while crossing a busy road, descending steep stairs, using power tools, or climbing a ladder.
So, pick a good time to ask someone a vexed question – perhaps not while they’re cutting vegetables with a sharp knife. Sometimes, it’s better to focus on one thing at a time.
Peter Wilson, Professor of Developmental Psychology, Australian Catholic University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
If humans disappeared, what would happen to our dogs?
Shutterstock Bradley Smith, CQUniversity Australia and Mia Cobb, The University of MelbourneFor many of us, dogs are our best friends. But have you wondered what would happen to your dog if we suddenly disappeared? Can domestic dogs make do without people?
At least 80% of the world’s one billion or so dogs actually live independent, free-ranging lives – and they offer some clues. Who would our dogs be if we weren’t around to influence and care for them?
What are dogs?
Dogs hold the title of the most successful domesticated species on Earth. For millennia they have evolved under our watchful eye. More recently, selective breeding has led to people-driven diversity, resulting in unique breeds ranging from the towering Great Dane to the tiny Chihuahua.
Humanity’s quest for the perfect canine companion has resulted in more than 400 modern dog breeds with unique blends of physical and behavioural traits. Initially, dogs were bred primarily for functional roles that benefited us, such as herding, hunting and guarding. This practice only emerged prominently over the past 200 years.
Some experts suggest companionship is just another type of work humans selected dogs for, while placing a greater emphasis on looks. Breeders play a crucial role in this, making deliberate choices about which traits are desirable, thereby influencing the future direction of breeds.
Are we good for dogs?
We know certain features that appeal to people have serious impacts on health and happiness. For instance, flat-faced dogs struggle with breathing due to constricted nasal passages and shortened airways. This “air hunger” has been likened to experiencing an asthma attack. These dogs are also prone to higher rates of skin, eye and dental problems compared with dogs with longer muzzles.
Many modern dogs depend on human medical intervention to reproduce. For instance, French Bulldogs and Chihuahuas frequently require a caesarean section to give birth, as the puppies’ heads are very large compared with the mother’s pelvic width. This reliance on surgery to breed highlights the profound impact intensive selective breeding has on dogs.
And while domestic dogs can benefit from being part of human families, some live highly isolated and controlled lives in which they have little agency to make choices – a factor that’s important to their happiness.
Dogs without us
Now imagine a world where dogs are free from the guiding hand of human selection and care. The immediate impact would be stark. Breeds that are heavily dependent on us for basic needs such as food, shelter and healthcare wouldn’t do well. They would struggle to adapt, and many would succumb to the harsh realities of a life without human support.
That said, this would probably impact fewer than 20% of all dogs (roughly the percentage living in our homes). Most of the world’s dogs are free-ranging and prevalent across Europe, Africa and Asia.
But while these dogs aren’t domesticated in a traditional sense, they still coexist with humans. As such, their survival depends almost exclusively on human-made resources such as garbage dumps and food handouts. Without people, natural selection would swiftly come into play. Dogs that lack essential survival traits such as adaptability, hunting skills, disease resistance, parental instincts and sociability would gradually decline.
Dogs that are either extremely large or extremely small would also be at a disadvantage, because a dog’s size will impact its caloric needs, body temperature regulation across environments, and susceptibility to predators.
Limited behavioural strategies, such as being too shy to explore new areas, would also be detrimental. And although sterilised dogs might have advantageous survival traits, they would be unable to pass their genes on to future generations.
No more designer breeds
Ultimately, a different type of dog would emerge, shaped by health and behavioural success rather than human desires.
Dogs don’t select mates based on breed, and will readily mate with others that look very different to them when given the opportunity. Over time, distinct dog breeds would fade and unrestricted mating would lead to a uniform “village dog” appearance, similar to “camp dogs” in remote Indigenous Australian communities and dogs seen in South-East Asia.
These dogs typically have a medium size, balanced build, short coats in various colours, and upright ears and tails. However, regional variations such as a shaggier coat could arise due to factors such as climate.
In the long term, dogs would return to a wild canid lifestyle. These “re-wilded” dogs would likely adopt social and dietary behaviours similar to those of their current wild counterparts, such as Australia’s dingoes. This might include living in small family units within defined territories, reverting to an annual breeding season, engaging in social hunting, and attentive parental care (especially from dads).
This transition would be more feasible for certain breeds, particularly herding types and those already living independently in the wild or as village dogs.
What makes a good life for dogs?
In their book A Dog’s World, Jessica Pierce and Marc Bekoff explore the idea of “doomsday prepping” our dogs for a future without people. They encourage us to give our dogs more agency, and consequently more happiness. This could be as simple as letting them pick which direction to walk in, or letting them take their time when sniffing a tree.
As we reflect on a possible future without dogs, an important question arises: are our actions towards dogs sustainable, in their best interests, and true to their nature? Or are they more aligned with our own desires?
By considering how dogs might live without us, perhaps we can find ways to improve their lives with us.
Bradley Smith, Senior Lecturer in Psychology, CQUniversity Australia and Mia Cobb, Research Fellow, Animal Welfare Science Centre, The University of Melbourne
This article is republished from The Conversation under a Creative Commons license. Read the original article.