As Year 12 students pass the halfway point of their final year, the question of “what next?” can start to loom large. Some students have a clear plan: a course they want to get into, a trade they want to start, or a gap year they are saving for.

But many find the question daunting, because the answer is, “I have no idea”.

If this is you, the first thing you need to hear is – not knowing is very normal. The second thing is – you do not need to know or decide your final destination now (or even soon).

Right now, you are being asked to make huge life decisions when you are still learning what you enjoy, what you are good at, the type of people you hope to work with, and what kind of life you want to build.

It is not realistic to think you will know all the answers to these questions at 17 or 18. These answers are supposed to reveal themselves over time, and they will.

Our research points to some strategies that may prove useful in moving forward, even if you don’t know exactly where you’re going yet.

Is my passion important?

One common approach you’ve probably tried is to ask yourself: what am I passionate about?

Personal interest can be a good starting point, but research suggests it’s not the whole picture.

All jobs have good and bad parts, and all futures have ups and downs. So the aim is not to expect constant enjoyment or getting everything you want. It’s to choose a next step that gives you a good chance of building toward a life that is meaningful, energising and right for you.

Our research finds this kind of life tends to emerge when three basic psychological needs are supported. These are:

1. autonomy – feeling like you’re in the driver’s seat of your life

2. competence – feeling like you can build skills and accomplish what needs to be done

3. relatedness – feeling connected to and valued by people you care about.

Everyone experiences the satisfaction of these needs differently, so you need to gather evidence about what satisfies yours.

What makes you feel capable and in control?

So, the task is not to find your passion. The task is to create good evidence about yourself.

Instead of asking “what job title do I want forever?”, ask:

• what kinds of tasks make me feel more capable after I do them?

• when do I feel curious rather than just compliant?

• what environments make me shut down or tune out?

• what kind of people do I want around me all day?

These questions matter because they will point you towards the kinds of experiences you want to have every day. Hopefully, this gives you a practical way to think about next year and a way to talk to people about it too.

Parents, teachers, career advisers, family friends, older students, and people working in fields you’re curious about are all a good start.

But remember, you need to feel in charge of your life. Bring them in on your evidence gathering rather than asking them to decide for you. Saying something like, “I’m open to advice. But I need support to do my own thinking,” might help.

As your time allows, try new things and be open. This might involve taking a class, getting a casual job, volunteering or joining a team. Pay attention to what leaves you feeling more skilled, connected and in control.

It’s OK not to know

My own career trajectory has been far from linear. I had many (many!) jobs across three full-time careers before I discovered my current career in academic research satisfies my needs. All the dots connected in the end, none of my previous experience was wasted.

I use myself as an example to show how the next step will not make or break your whole life.

So choose a next step that is realistic, builds skills, and is most likely to support those basic psychological needs.

The form of that choice matters less than whether it gives you room to grow, build confidence, meet people, and gather better information about yourself.

Emma Bradshaw, Research Fellow, Motivation and Behaviour, Australian Catholic University

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

Images of the sleek keels, elegant planks, and dragon-headed prows of Viking longships have been reproduced countless times on postcards, book covers, souvenirs and in television shows and movies.

These vessels are, quite literally, the poster-ships for the Viking Age, which was between around 750 and 1100 CE.

So what made these ships so special? And why were these advanced shipbuilding techniques so crucial to the Vikings’ success?

What drove this shipbuilding boom?

In Old Norse, there are two words for Viking: víkingr refers to a person, while víking is an activity. Neither word is inherently negative nor associated with violence.

A víkingr is someone (who may or may not identify as a pirate) who undertakes víking expeditions (sometimes to pillage, sometimes not), and whose life and livelihood have strong connections to the sea.

By the mid-eighth century, these people were keen to expand their horizons and branch out from local economies.

This coincided with a number of large and lucrative mercantile towns springing up around north-west Europe in this period.

Among other factors, Vikings travelled further westward and eastward as part of an ongoing and complex power grab for portable wealth, territory, and control of trade routes.

From the 750s on, the Vikings’ advanced shipbuilding technology helped give them the edge.

Gamechanging technology

The unique design of Viking ships and their trademark square sails were absolute gamechangers in this period.

There are many different types of Viking ship, but the most relevant here are the langskip (longship) and knörr (cargo ship).

Like all Viking vessels, these are clinker built. That means the hull’s long, curved sides are assembled out of slightly overlapping planks, and are held together by iron nails (the “clinkers”).

Along with their strong but slender keels and stems, this innovative construction made for incredibly flexible, light, and sinuous vehicles that could be powered by oars or by sail and withstand wild ocean swells.

With their narrow silhouettes and their ability to gently twist and yield to the waves, it’s no wonder longships were called snekkja (serpents), dreki (dragons) and skeið (sliders).

Another small but significant improvement that made longer-distance travel possible was the oar-hole.

Until the early Viking Age, pegs called tholepins stuck up from the gunwales (upper rim of the boat) to hold oars in place and act as fulcrums for rowing. This meant ships’ sides could never be very high above the water. (Imagine trying to row with your oar at head height.)

But by cutting holes through the side planks, which could be plugged when the oars were shipped and the sail raised, it became possible to build taller, more seaworthy ships.

The boats had shallow drafts (meaning not much of it was under the waterline). This enabled these “sea-snakes” to slither further inland than ever before, since they could tackle riverways other boats simply couldn’t navigate. They could also be dragged across land.

Longships also had symmetrical prows (meaning the “back” of the boat was just as high as the “front”).

This design allowed Viking raiders to pull right up on the riverbank, then “hit and run” – without all the slow awkwardness of reversing and turning the whole boat around for the getaway.

Square sails also increased both the distance and speed of Viking travel. Norse explorers like Eirik rauða (“the Red”) and his son Leif (who went to North America nearly 500 years before Columbus) wouldn’t have taken a warship to Iceland or Greenland.

Instead, they probably kitted out a knörr, a heavy-bellied merchant ship much like the one described in an ancient Icelandic text called Egil’s saga

richly painted above the plumbline and fitted with a black-and-red sail […] loaded with stockfish, hides and ermine, and a great quantity of squirrel skins and other furs […] a very valuable cargo.

When powered by four oars, a modern reconstruction of just such a knörr reached a speed of 1.5 knots. With the sail raised it sped along at 13 knots (around 24 km an hour).

A much larger longship with 60 oars could row at 4.5 knots and reach a maximum sailing speed of 17 knots (31.5 km an hour)!

Crafted by hand

The most impressive stats about Viking ships aren’t about how fast or far they went, but rather how much time, effort, and natural resources went into building them. The sheer industry of it all is astonishing.

Every piece was crafted by hand. Axes shaped the floor timbers, planking, masts and beams.

Dozens of oak trees (8-10 metres long and at least a metre across) went into the hull. Dozens more pine trees were burnt to make tar for sealing the wood (600 litres for a 60-oar longship, which took more than 2,000 hours to produce).

More pine and alderwood went into the oars and mast.

Then there’s all the iron: 450kg of it to make the 8,000 nails needed for this same longship.

An average knörr’s sail was 90m² (smaller than the longship’s) and used the wool of 200 sheep, all of which had to be spun into thread and woven into continuous lengths of fabric, each 65cm wide.

This spinning and weaving work took experimental historians 7,850 hours to recreate (around 4.5 years for one person).

Another month was needed to sew the sail panels together, cut it to shape and reinforce its edges. Then there’s the ship’s cordage: so much horsehair, hemp and linden bast (a plant fibre) for 3,000 metres of rope.

This constant and large-scale manufacturing paints an evocative picture of the Vikings’ everyday, shipbuilding life.

It was all hands on deck, so to speak.

Lisa Bennett, Associate Professor in Creative Writing and English Literature, Researcher in Old Norse Literature, Flinders University

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

Are you surrounded by screens?

Today, we rely on technology to do everything from sending emails to ordering food. But being constantly connected can leave us physically and mentally exhausted.

That’s why some people are doing “digital detoxes”, the practice of staying away from devices and social media for a set period of time.

The concept is gaining traction online, with supporters spruiking the health benefits of the “analogue lifestyle”. Some are even paying big bucks to go on “digital retreats”, with the aim of becoming healthier and happier.

But do digital detoxes actually work, or are they just another wellness trend?

What is a ‘digital detox’?

The term “digital detox” stems from detoxification, the process of safely getting a person off an addictive substance such as alcohol or drugs. This is usually done with support from a health-care professional.

So the idea of a digital detox is to step away from technology, to instead experience life with fewer distractions and foster relationships offline.

The trouble with tech

On average, young people in Australia look at screens for nine hours a day. Research suggests adults aren’t much better, with Australians aged between 45 and 64 spending up to six hours each day on screens.

As a result, more people are experiencing information overload, the idea of being physically and emotionally overwhelmed by an immense amount of data. A related concept is social media fatigue, a consequence of being constantly connected through online platforms.

But there are signs people are resisting the pull of technology. Some younger people are swapping screens for hands-on hobbies such as knitting, and joining chess clubs and other offline social activities.

They are also driving trends such as “raw-dogging boredom”, the practice of sitting through long haul flights without headphones. And friction-maxxing, the idea you can become a better, more resilient person by doing tasks that involve some level of difficulty, is also gaining traction online.

So in a sense, digital detoxes are just the latest online trend.

Do ‘digital detoxes’ work?

Current research suggests digital detoxes may have some benefits. But the evidence is far from conclusive.

One 2025 meta-analysis examined 20 randomised controlled trials, all looking at the effects of social media detoxes. It found taking a short break from social media had a small but positive effect on people’s feelings of life satisfaction and self-esteem. Participants also reported feeling less anxious, depressed and lonely.

In another 2025 study, researchers blocked participants’ smartphones so they could only receive calls and texts, over a two-week period. The results were striking. The researchers found this intervention had a greater positive effect on participants’ mental health than antidepressants. Importantly, this was because participants spent less time on their phones, but also spent this time doing beneficial activities such as socialising in person, exercising and being in nature.

Not for everyone

Digital detoxes may impact people differently, due to various factors.

One is cultural context. Research suggests people using social media in collectivist cultures such as Turkey may experience more social pressure to respond quickly and maintain extensive networks, compared to those in more individualistic societies. So people in collectivist cultures may benefit more from taking a break from social media.

Another is gender. Research suggests women mainly use social media to maintain relationships, and that they compare their physical appearance to others. This means they may benefit more from a digital detox, compared to men. One 2020 study found women who took a one-week break from Instagram felt significantly more satisfied with their life than women who stayed on it. However, the researchers did not see the same effect in men.

All about the approach

Current research suggests doing a digital detox may improve your mental health. But the way you approach it matters.

You shouldn’t just go cold turkey on technology. That’s because you’re less likely to sustain that change. One 2023 study found people who reduced their daily smartphone use by one hour experienced stronger and more lasting mental health benefits, compared to those who quit entirely.

Here are some tips to make your digital detox last:

• identify any unhelpful habits, for example checking your phone too often or bringing it everywhere

• make a plan to change those habits, for instance setting app time limits or only checking messages at certain times

• set specific goals, such as taking a break from Instagram for one week

• share your goals with family and friends, both so they can support you and understand why you may not reply to their messages

• monitor your progress, for example by reflecting on whether you feel less anxious or are sleeping better.

It’s hard to stay present and connected in our increasingly digital world. But doing a digital detox could help. Importantly, the aim is not to eliminate technology from your life, but to use it in a more conscious, deliberate way.

Joanne Orlando, Researcher, Digital Wellbeing, Western Sydney University

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

All working Australians will receive a permanent $250 “tax offset” from next year in Treasurer Jim Chalmers fifth budget, which also cracks down on tax breaks for housing investors and trusts.

The tax offset in the budget will cost nearly $6.4 billion over the forward estimates.

Delivering the budget on Tuesday night Chalmers told parliament: “This [package] will help rebalance a system which is more generous to assets than it is to labour”.

As was widely predicted, the budget will limit negative gearing for housing to new builds from July next year.

But existing negatively geared properties will be “grandfathered” out of the change.

The 50% capital gains tax discount, will be replaced with an inflation-adjusted indexation.

This will apply to other assets, such as shares, as well as investment housing.

Chalmers told parliament: “our tax changes will help about 75,000 Australians achieve the dream of home ownership”.

Shadow Treasurer Tim Wilson flagged a fight over the housing tax changes. “We won’t be supporting these measures because it fundamentally undermines the pathway for young Australians […] to be able to buy their first home.”

Chalmers said the budget included “the most significant tax reform package in more than a quarter of a century”.

“This is about tax relief and tax reform to make our economy work for more Australians, businesses and future generations.”

“We’re delivering a fairer tax system for workers, first home buyers and future generations.”

The government is also introducing a minimum 30% tax rate on net capital gains from July next year, and on discretionary trusts from July 2028.

Chalmers said Treasury was now forecasting inflation to peak at about 5% because of the Middle East conflict.

“For the same reasons, it’s expecting growth to come in half a percentage point lower next financial year, to be 1.75% overall.”

He also presented “a more severe scenario” of what could happen, where the oil price peaked at US$200 before taking three years to come back down.

“We would still avoid a recession, but unemployment would spike to pre-pandemic levels and inflation would peak above 7%.”

Annual real wage growth is forecast to return from next year, while unemployment is expected to remain in the mid fours.

The budget deficit in the next financial year is projected to be $31.5 billion which is $2.8 billion better than earlier predicted.

Chalmers said the bottom line is expected to be better in every year over the forward estimates and the medium term.

“The budget position has improved by $44.9 billion and this makes it more than a quarter of a trillion dollars better than when we came to office.”

But the budget remains in deficit over the forward estimates and is not forecast to return to surplus until the mid 2030s.

Gross debt is forecast to be $982 billion at the end of this financial year. Chalmers described the budget as “ambitious in the face of adversity”.

“It’s a responsible budget, and a reforming budget, which builds resilience and bolsters our economy.

"There is more cost-of-living relief, more Medicare and more aged care, and more housing.

"It makes the tax system fairer and stronger for workers, businesses, first home buyers and future generations.”

The budget forecasts that Net Overseas Migration will be 295,000 for 2025-26 dropping to 245,000 in 2026-27.

Most of the major changes in the budget had been pre-announced, including the establishment of a new fuel security regime, an extensive haircut to the National Disability Insurance Scheme and $53 billion over the next ten years for defence.

Michelle Grattan, Professorial Fellow, University of Canberra

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

Every four years, the men’s World Cup delivers some certainties. The pitch dimensions are tightly regulated, offside is signaled with a flag, and referees end the match with a blast of a whistle. But one key piece of equipment is changed on purpose: the ball.

Adidas, which has supplied World Cup soccer balls since 1970, introduces a new match ball for every tournament, and with that comes fresh aerodynamic calculations for players. How will it fly through the air, weave and dip?

For the past 20 years, my engineering colleagues in Japan and England and I have put the new balls through their paces, investigating soccer ball aerodynamics. Our work begins by putting balls in wind tunnels to measure drag, side and lift forces. We use the measurements from these tests in trajectory simulations that tell us how the ball will behave in a real-game setting.

That may all sound a little academic, and we do produce an academic paper on our findings. But what our data indicates could mean the difference between a goal or a miss for strikers, a save or a blunder for goalkeepers, and jubilation or heartache for fans.

At the World Cup, the ball is the most important piece of equipment in the biggest tournament of the world’s most popular sport.

This year’s ball, the Trionda, is especially interesting. When FIFA and Adidas unveiled it in fall 2025, the first thing many people noticed was the color and the paneling.

The ball’s red, blue and green graphics correspond to the three host countries, with maple leaf, star and eagle motifs representing Canada, the United States and Mexico. And for the first time in men’s World Cup history, matches will be played with a four-panel ball.

But with so few panels, has Adidas made the ball too smooth? That is the trap engineers fell into with the Jabulani ball used at the 2010 World Cup in South Africa that became notorious for sudden dips and swerves, which made goalkeepers’ lives far trickier.

You do not want the World Cup ball to feel like the start of a science experiment once it is in the air. And if it behaves strangely, players and goalkeepers notice immediately.

The evolution of soccer balls

World Cup balls have come a long way over the decades. If you go back to 1930, the ball looked very different. The first World Cup final used two different leather balls: Argentina’s Tiento in the first half and Uruguay’s T-Model in the second. Both were hand-sewn, multipaneled balls, inflated through a bladder opening that had to be tied off and tucked back beneath the laces. In damp conditions, the leather absorbed water, making the ball heavier and less predictable in play.

By 1994 – when the United States last hosted the men’s tournament – the official ball, Adidas’ Questra, had evolved into a foam-based design. The modern World Cup ball is no longer just stitched leather. It is an engineered aerodynamic surface.

Trionda pushes that evolution further. It has only four panels, the fewest in men’s World Cup history, which have been thermally bonded – melded together using heat and adhesive.

Fewer panels might suggest less total seam length and therefore a smoother ball. And smoothness matters because the thin boundary layer of air clinging to the ball determines where the flow separates, how large a wake forms, and how much drag the ball experiences.

The Trionda has intentionally deep seams, three pronounced grooves on each panel and fine surface texturing.

But will these textures and grooves do the trick? To find that out, my colleagues and I measured the ball’s seam geometry and overall aerodynamic behavior. We compared it with Trionda’s four predecessors: 2022’s Al Rihla, 2018’s Telstar 18, the Brazuca used in 2014 and the Jabulani in 2010.

What the measurements show

In our wind tunnel tests at the University of Tsukuba, we measured something called the drag coefficient, which is a way of describing how much air resistance a ball experiences as it moves.

Using this data, we gained insights into how the airflow changes around the ball after it is kicked. The tests helped identify the drag crisis, the speed range in which changes in the boundary layer and flow separation produce a sharp change in drag, which can alter the ball’s acceleration, trajectory and range.

We found that the Trionda is effectively rougher than those predecessors.

Trionda reaches its drag crisis at a lower speed, at about 27 mph (43 kph). That is below the roughly 31-40 mph (50-65 kph) range for Al Rihla, Telstar 18 and Brazuca, and far below Jabulani’s roughly 49-60 mph (79-97 kph) range, depending on orientation.

Why does all that matter? Because a ball can feel ordinary off the boot and still behave differently in flight. When the drag crisis occurs in the middle of game-relevant speeds, small changes in launch speed, orientation or spin can shift the ball from one aerodynamic regime to another.

That was Jabulani’s problem. Once kicked with little spin, it had a tendency to slow down too much as it passed through its critical-speed range.

Trionda does not look like that kind of ball. It has a more steady and consistent drag coefficient in the range of speeds associated with corner kicks and free kicks.

But there is a trade-off. Our measurements also showed that once Trionda enters the higher-speed, turbulent-flow regime, its drag coefficients are somewhat larger than those of Brazuca, Telstar 18 and Al Rihla.

In plain language, that suggests a hard-hit long ball may lose a little range.

In our simulations, the difference is not huge. But it is large enough that players may notice long kicks coming up a few meters short.

It is also important to note that we tested a nonspinning ball. As such, our results do not provide a prediction of every pass, clearance or free kick fans will see this summer. Balls in flight often spin due to off-center kicks. That, along with altitude, humidity, temperature and air pressure all influence how a ball flies through the air once kicked.

The big test yet to come

Fewer panels and more texturing aren’t the only differences with the new ball.

Trionda also carries technology that has little to do with its flight and a great deal to do with officiating. Like Al Rihla, Trionda includes “connected-ball technology” that lets computers know when the ball is kicked, helping with offside decisions.

But the architecture has changed. In 2022, the measurement unit was suspended at the center of the ball. With Trionda, it sits in a specially created layer inside one panel, with counterbalancing weights in the other three panels. The chip sends data to the video assistant referee, or VAR, system and the tournament’s semi-automated offside system.

That tweak will help referees, but will the new ball in general help or hinder players?

The evidence from our tests suggests that the ball won’t be behaving in a way that leads to baffling and erratic flight.

But the more intriguing possibilities are subtler and outside the scope of our tests. Will the grooves on Trionda help players generate more backspin on the ball, generating more lift and possibly offsetting Trionda’s somewhat larger high-speed drag coefficient?

That is why I keep studying World Cup balls both in the lab and through their behavior in play. Every four years, a new design offers a fresh way to watch physics enter the game, not in theory, but in the movement of an object in which every player on the soccer field must place their trust.

John Eric Goff, Visiting Assistant Professor, Physics, University of Puget Sound

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

When you think of outer space, you’re likely picturing stars, planets and moons. But much of space is filled with clouds of gas, plasma and stardust – known as interstellar clouds.

In the local parts of our galaxy alone there’s a complex of roughly 15 individual interstellar clouds. The Solar System is currently traversing one of them, aptly named the Local Interstellar Cloud. The origin and history of these clouds are believed to be tightly connected to the birth and death of stars. But we can see their imprints right here on Earth, in a place you might not expect – Antarctic ice.

My colleagues and I have been studying stardust trapped in old Antarctic snow and ice to trace the history of our solar neighbourhood, including the Solar System itself.

In a new study published in Physical Review Letters, we found a subtle clue that reveals our Solar System’s movement through the local interstellar environment over the past 80,000 years.

Looking down to see the sky

Astronomy usually looks outward. Telescopes collect light from distant stars and galaxies, allowing us to observe events across vast stretches of space and time. From these observations, we infer how stars live and die, how elements are formed, and how the universe evolves.

Our approach turns that idea on its head.

Instead of observing the light coming to us, we study the debris of exploding stars right here on Earth. As cosmic furnaces, stars forge many elements in their cores, from carbon and oxygen to calcium and iron. This includes rare isotopes (variants of chemical elements) such as iron-60.

When massive stars explode into supernovae at the end of their life, these elements are ejected into space and become interstellar dust.

Tiny grains of this dust then drift through the galaxy and occasionally find their way to Earth’s surface. Radioactive iron-60, a fingerprint of stellar explosions, is embedded within these grains. By searching for these atoms in geological archives on Earth, we can probe astrophysical events like supernovae long after their light has faded.

This is why Antarctica is so valuable. Its snow accumulates slowly and remains largely undisturbed, forming a layered record that stretches back tens of thousands of years. Each layer captures a snapshot of the material that was present in our cosmic neighbourhood at the time.

Finding stardust in Antarctic ice

When we studied 500kg of recent snow in Antarctica, we unexpectedly found this rare radioactive isotope. Where did it come from? There was no recent near-Earth supernova.

But our solar neighbourhood is filled with 15 clouds, with the Solar System currently traversing at least one of them. Is the stardust waiting in the clouds to be picked up by Earth? If yes, then the amount of stardust Earth collects should be related to their structure: the denser the clouds, the more iron-60 they contain. This was our educated guess in 2019.

Soon, other explanations were brought forward. Millions of years ago Earth received large showers of iron-60 from massive supernovae. Is the iron-60 in Antarctic snow the last remnant or an echo of this signal? A rain that became a drizzle?

To find out, we analysed a 300kg section of Antarctic ice, dating from 40,000 to 80,000 years ago. The process is painstaking. The ice needs to be melted and chemically treated to isolate tiny amounts of iron, including the iron-60 from the stardust.

Then, using the sensitive atom counting technique of accelerator mass spectrometry at the Heavy-Ion Accelerator Facility at Australian National University, we counted individual atoms of iron-60.

The expectation was straightforward: based on previous measurements from surface snow of Antarctica and several thousand-year-old ocean sediments, we anticipated a certain steady level of iron-60 deposition.

Instead, we found less. Not zero, but noticeably lower than expected.

This result suggests that less interstellar dust was reaching Earth during that period. This is a remarkable change on a comparatively short astrophysical timescale and does not fit the long timescales of the iron-60 deposits that landed here millions of years ago. Instead, we needed to look for a smaller, more local source for the isotope.

A fitting story

Naturally, astronomers are also quite interested in the clouds around the Solar System. Last year, a study reconstructing the history of the clouds arrived at the conclusion that they most likely originated in a stellar explosion. Furthermore, they found the Solar System has been traversing the Local Interstellar Cloud from sometime between 40,000 and 124,000 years ago.

If that’s correct, we would expect that the amount of iron-60 collected on Earth should have changed sometime in the same time period – between 40,000 and 124,000 years ago.

This is exactly what our results showed in Antarctica.

The story doesn’t fit perfectly, though. If these clouds did originate directly from an exploding star, we would expect way more iron-60 than we actually see in Antarctic ice.

Nevertheless, these clouds are imprinted in Earth’s geological record. If we look deeper and analyse even older ice, we might soon unravel the mystery of these local interstellar clouds, revealing their full history and uncertain origins.

Dominik Koll, Honorary Lecturer, Nuclear Physics, Australian National University

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

You’re trying to book concert tickets before they sell out. You click the link and before you can make the payment, you’re asked to identify traffic lights, bicycles or blurry crosswalks in a grid of tiny images.

Again.

For many people, this has become a routine part of life. Logging into financial apps, shopping online or creating accounts increasingly involves “proving you are human”.

These systems are known as CAPTCHA. Why are they everywhere?

The short answer is that websites are fighting a rapidly escalating war against bots: automated software that imitate human behaviour online. And thanks to advances in artificial intelligence (AI), those bots are becoming even smarter, cheaper and harder to detect than ever before.

Why websites need proof you are human

Huge amounts of online traffic now come from automated systems. Some are helpful, such as search engine crawlers indexing pages for Google search.

Others are far less welcome, and may involve phishing, spam, fake accounts, passwords violation, misinformation, and distributed denial of service attacks overloading web servers. In some areas, AI agents now generate automated online traffic that exceeds human traffic altogether. Modern AI systems can generate convincing text, imitate browsing patterns and even solve some CAPTCHA puzzles.

At the same time, companies are increasingly worried about bots scraping online content to train AI systems.

As a result, more websites are adding verification systems simply to keep abuse under control.

How CAPTCHA actually works

CAPTCHA stands for “Completely Automated Public Turing test to tell Computers and Humans Apart”. The original idea was simple: give users a task humans find easy, but computers find difficult.

Early CAPTCHA systems often involved distorted text. Later versions switched to image-recognition tasks such as selecting all the squares containing traffic lights or bicycles. Google’s reCAPTCHA became one of the best-known examples. Earlier versions even helped digitise books and improve street-view image recognition while users solved puzzles.

But computer vision has improved rapidly in recent years. Advances in AI mean bots can now solve many traditional CAPTCHA challenges surprisingly well. Researchers have repeatedly shown that modern AI systems can bypass some CAPTCHA systems with high success rates.

That is why today’s CAPTCHA systems rely less on puzzles and more on behavioural analysis.

When users click the CAPTCHA link, the system analyses many background signals, such as mouse movements, typing speed, IP addresses, device information, and interaction timing that reflect human behaviours. Humans tend to behave in inconsistent ways. Bots are usually more predictable.

If the system is sufficiently confident you are human, you may never see an image puzzle at all. But if something appears suspicious, the system may trigger harder tests.

Moving beyond traditional CAPTCHA puzzles

While some bots now use AI capable of solving image-recognition tasks, others simply outsource CAPTCHA solving to cheap human labour services, where real people complete challenges for a small payment. This has turned CAPTCHA into an ongoing arms race. That may explain why CAPTCHA tests often feel harder and more frustrating than they used to.

As AI continues to improve, websites will likely move beyond traditional CAPTCHA puzzles. Future systems may increasingly rely on behavioural biometrics, such as typing rhythm or scrolling style, device verification systems, invisible background risk scoring, and AI systems designed to detect other AI systems.

In many cases, users may no longer even notice the verification process happening.

CAPTCHA tests may seem like a minor annoyance, but they reflect a much larger paradigm shift online. For decades, websites largely assumed visitors were human. Increasingly, that assumption no longer holds. As AI-generated traffic continues to grow, proving we are human online may become an even more common part of everyday life.

Yang Xiang, Professor, Computer Science, Swinburne University of Technology

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

Few phrases in literature have travelled as widely as “all for one, and one for all”. It has come to signify loyalty, courage and a form of friendship that appears to transcend circumstance.

First published in 1844 in serial form, The Three Musketeers by Alexandre Dumas (1802–1870) quickly established itself as one of the most compelling adventure narratives of the 19th century. Dumas was among the most prolific and widely read writers of his age, working across drama, journalism, travel writing and historical fiction on an extraordinary scale.

His major novels, including The Count of Monte Cristo (1844–46) and the cycle of novels featuring the young adventurer Gascon d’Artagnan, incorporating The Three Musketeers, Twenty Years After (1845) and The Vicomte of Bragelonne (1847-50), were shaped by serial publication, which demanded pace, suspense and strong character differentiation.

At the same time, as lesser-known works such as Isaac Laquedem (1852–1553) suggest, Dumas conceived of his writing not only as popular entertainment, but as ambitious historical narrative on an epic scale.

This dual orientation, to mass readership and large-scale historical imagination, helps explain the structure of The Three Musketeers, where vivid character types, rapid plotting, and historical setting combine to produce a narrative that is at once accessible and enduring.

History and narrative

Recent developments have returned attention to the historical figure behind the story. In March 2026, archaeologists in Maastricht uncovered remains believed to belong to Charles de Batz de Castelmore (c.1611–1673), also known as d’Artagnan, reportedly killed during the siege of the city during the Franco-Dutch War.

Scientific confirmation remains pending. Yet the discovery matters less for what it proves than for what it reveals: the persistent overlap between history and narrative. Dumas’s novel has long occupied that space, drawing authority from the 17th century, while reshaping it for 19th-century readers.

Set in France during the reign of Louis XIII (r.1610–1643) and shaped by the political reach of Cardinal Richelieu (in office 1624–1642), The Three Musketeers brings together court intrigue, ambition and honour in a tightly constructed narrative world.

From the outset, Dumas signals that he is not writing history in a strict sense. Drawing on supposed memoirs and anecdotal fragments, he constructs a world defined by rivalry, violence and performance.

This is not a flaw but a method. The novel’s enduring appeal rests not on historical accuracy, but its capacity to distil and dramatise ideals: comradeship, honour and masculine identity. These are not stable conditions; they are values under pressure, shaped by the political culture of early modern France.

The narrative begins with the arrival in Paris of the young d’Artagnan, a provincial outsider seeking advancement in the royal service. His ambition reflects the social mobility of the period, even within a hierarchical society.

Through a chain of misunderstandings, he offends Athos, Porthos and Aramis, arranging to duel each in turn. Yet this ritualised violence, rooted in the honour culture of the 17th century, produces an unexpected outcome. When confronted by the guards of Richelieu, the four men fight together and emerge as allies. Conflict becomes the basis of solidarity.

From this moment, the personal and the political become inseparable. The narrative draws in the court of Anne of Austria, queen consort of France from 1615, and her connection with the English courtier George Villiers (1592–1628), whose influence in Anglo-French relations shaped the politics of the 1620s.

The result is a world structured by secrecy, surveillance and manipulation. Episodes such as the quarrel at Meung, when d'Artagnan is affronted by a man who mocks his shabby horse, or the Musketeers’ recovery of the queen’s diamonds are set against the backdrop of wider tensions, including the lead-up to the Siege of La Rochelle (1627–28).

Chance and calculation operate together, but always within a defined political order.

Models of masculinity

At the centre of the novel stand four figures whose differences are as important as their unity. Their bond, expressed in their famous motto, does not arise from likeness but from contrast. Each represents a distinct model of masculinity shaped by the social and political expectations of the early 17th century.

Athos embodies restraint and authority. Marked by a concealed past, he reflects an older aristocratic code rooted in lineage and honour. His authority derives from self-control rather than display, recalling a model of noble identity already under strain in the 1620s.

Porthos operates through display. His concern with wealth, clothing and reputation reflects a world in which status must be asserted as well as inherited. His performative masculinity reveals the instability of rank in a society where appearance and recognition are closely linked.

Aramis is divided between religious vocation and worldly ambition. His career reflects the continuing entanglement of church and state in 17th-century France. His duplicity mirrors a political culture in which allegiance is rarely singular.

D’Artagnan is the outsider navigating this system. As a provincial noble of limited means, he represents a form of social mobility tied to service and merit. His success depends on his ability to read and adapt to a changing political environment.

These four men do not form a natural unity. Their friendship is constructed through duels, shared risks and mutual dependence. It is sustained by adherence to a code of honour rooted in the practices of their time. Their bond is contingent and historically grounded.

The motto “all for one, and one for all” should be read in this light. It expresses an aspiration rather than a condition. The bond it describes must be enacted within a culture that constantly tests it.

Duelling culture provides the mechanism for this enactment. Violence is not an anomaly, but a recognised part of aristocratic life in 17th-century France. Honour is defended publicly; identity is secured through action. The transformation of rivalry into solidarity is not accidental, but structural.

This model of comradeship rests on three elements: loyalty, risk and shared violence. Each reinforces the others. Trust is established through danger, and collective identity overrides individual interest when required. Friendship becomes a practice rather than a feeling.

Such a model differs sharply from modern conceptions of friendship. Where contemporary ideals emphasise choice and emotional affinity, Dumas presents a form of association shaped by obligation and discipline. It reflects the conditions of its historical setting.

Politics in the novel follows the same pattern. It is performative rather than transparent. Power operates through networks, intermediaries and controlled displays of loyalty. Richelieu’s authority rests as much on information and influence as on formal position.

Within this system, allegiance is unstable. The Musketeers serve the king, yet act with a degree of autonomy that reflects the fluidity of early modern political structures. Intrigue becomes the normal mode of engagement.

Loyalty, honour and friendship

Women play a decisive role in this political world. Anne of Austria’s position is both central and precarious, shaped by dynastic politics and international alliances. D'Artagnan’s love interest Madame Bonacieux, though socially modest, becomes a conduit for political action.

Their roles show that power extends beyond formal institutions. Through these figures, Dumas demonstrates how private relationships shape public outcomes. Emotional ties become political forces. The distinction between personal and political collapses, reflecting the realities of court society.

The novel’s continued relevance lies in this clarity. Its themes remain legible because they are historically grounded, yet structurally recognisable. Loyalty is tested, honour is contested, and friendship becomes a form of identity.

The cultural afterlife of The Three Musketeers reflects this. Across numerous adaptations, the figures of d’Artagnan and the Musketeers remain recognisable because they embody enduring patterns of association rather than fixed historical realities.

The appeal lies in precision rather than simplicity. The moral framework is clear, even when outcomes are uncertain. The narrative’s pace conceals a consistent structure grounded in historical context.

“All for one, and one for all” endures because it articulates a solution to a persistent problem: how to sustain unity in a world defined by competition and mistrust.

The novel does not resolve this tension. Instead, it stages it within the political and social conditions of 17th-century France. The Musketeers’ bond is fragile, shaped by ambition, pride and circumstance. But it holds because it is continually reinforced.

In this sense, The Three Musketeers offers not a record of the past but a historically grounded model of association. It suggests solidarity is possible, but only under conditions of risk and mutual obligation.

That is why the motto persists. It names an ideal that is difficult to realise, yet difficult to abandon. Amid strained alliances and shifting loyalties of our own time, it reads less as nostalgia than as a challenge: not what such unity once meant, but whether it can still be sustained.

Darius von Guttner Sporzynski, Professor of History, Australian Catholic University

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

Four percent of Americans – roughly 12 million people – believe that “lizard people” secretly control the Earth. At least, that was the finding of an infamous 2013 public opinion survey.

Do so many people really believe such outlandish claims? Or do results like these partly reflect people giving silly answers or deliberately skewing surveys for fun?

US psychiatrist Alexander Scott believes the latter plays a significant role.

Using the survey as an example, he coined the term “the Lizardman constant” to describe the idea that a certain amount of noise and trolling will always exist in surveys about unusual beliefs.

As Scott warned: “Any possible source of noise – jokesters, cognitive biases, or deliberate misbehaviour – can easily overwhelm the signal.”

As researchers who study uncommon beliefs such as conspiracy theories, we wanted to investigate how this kind of cheeky trolling can muddy the waters.

Trolls and true believers

Building on earlier Australian research, we surveyed New Zealanders to test how common dishonest or joking responses were in conspiracy theory surveys.

We did this in two ways. First, we directly asked people a yes/no question at the end of the survey:

“Did you respond insincerely at any earlier point in this survey? In other words, did you give any responses that were actually just joking, trolling, or otherwise not indicating what you really think?”

Second, we included in the survey a “conspiracy theory” so ridiculous we could assume most, if not all, people who said they believed it were taking the mickey.

We asked them if they believed:

The Canadian Armed Forces have been secretly developing an elite army of genetically engineered, super intelligent, giant raccoons to invade nearby countries.

In our representative online sample of 810 New Zealanders, 8.3% of respondents confessed to being insincere in the survey.

Another 7.2% said they thought the Canadian raccoon army theory was probably or definitely true. That proportion – similar to findings from Australia – would equate to more than 300,000 adult New Zealanders.

To complicate things slightly, there was some overlap between those admitting to insincere answers and those claiming to believe the raccoon conspiracy. Combined, 13.3% of respondents fell into one or both groups – roughly one in eight people not appearing to take the survey seriously.

Importantly, these respondents were also much more likely to endorse other conspiracy theories, inflating estimates of how widespread those beliefs really are.

For instance, 6.5% of the full sample endorsed the claim that governments around the world are covering up the fact that 5G mobile networks spread coronavirus.

But once we removed the insincere responders, that figure dropped by more than half to 2.7%.

Across 13 different conspiracy theories, the estimated proportion of believers fell substantially once those respondents were excluded.

Another interesting insight from our study was that people endorsing contradictory conspiracy theories were much more likely to show signs of responding insincerely.

Previous studies have found some people appear to believe conspiracy theories that directly contradict each other. In our survey, for example, some participants agreed both that COVID-19 is a myth and that governments are covering up the fact that 5G networks spread the virus.

But nearly three-quarters of those respondents also showed signs of joking or dishonest answers.

This suggests genuinely believing contradictory conspiracy theories may be less common than previously thought.

Not every conspiracy believer is joking

Our findings add further weight to the idea that surveys may overestimate how many people truly believe some conspiracy theories – thanks, in part, to trolls.

But does that mean all conspiracy theory research is bunk?

Fortunately not. Most research in this area is not focused on counting conspiracy believers, but on understanding why people hold these beliefs and what effects they can have.

We tested several well-established findings from earlier conspiracy theory research to see whether they still held up once insincere respondents were removed from the data.

For example, previous studies have found that people who endorse conspiracy theories are more likely to see the world as a dangerous and threatening place.

We found the same pattern. In fact, removing insincere respondents made little difference to the broader relationships identified in earlier research.

Nevertheless, we recommend that future surveys include ways to gauge whether respondents are answering sincerely and account for this in the analysis. At the very least, researchers should acknowledge that trolls and joking responses can distort their results.

While our research suggests some people are taking the mickey in surveys, it also shows a significant minority genuinely appear to believe some of these claims.

In some cases – such as believing authorities are covering up the fact that the Earth is flat – this may be relatively harmless. But other conspiracy beliefs can lead to real-world harm.

Good-quality research is essential for understanding how sincere believers end up down these rabbit holes, and how those beliefs influence real-world behaviour.

Research into why people embrace conspiracy theories – and the real-world consequences of those beliefs – remains important.

But when surveys suggest millions may believe in lizard overlords or genetically engineered raccoon armies, it is also worth remembering the “Lizardman constant”: some respondents may simply be having us on.

The authors acknowledge the contributions of Rob Ross, Mathew Ling and Stephen Hill to this article.

John Kerr, Senior Research Fellow, Department of Public Health, University of Otago; Mathew Marques, Senior Lecturer in Social Psychology, La Trobe University, and Matt Williams, Associate Professor in Psychology, Te Kunenga ki Pūrehuroa – Massey University

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

Archaeologists have found something unexpected inside a 1,600-year-old Roman-era Egyptian mummy: a fragment of Homer’s Iliad. It wasn’t placed beside the body, but inside the mummy’s abdomen. But the real surprise isn’t just where the fragment was found. It’s how it got there. To understand, we must go back – to the Iliad itself, and to what it became in the Roman world.

In The Iliad, a poem shaped in the 8th century BC and attributed to Homer, the Trojan war does not end in triumph or renewal. It ends in devastation. The poem closes at the edge of collapse, with Troy reduced to a landscape of heroic ruin. And yet, this is not where the story ends.

According to later Roman tradition, one Trojan escaped. Aeneas – son of Anchises and the goddess Aphrodite – fled the burning city carrying his father on his shoulders and the household gods in his hands. He moved west, across the Mediterranean, towards Italy, where he became the ancestor of Rome.

This continuation did not come from the Iliad itself. It was shaped centuries later, most famously in Virgil’s Aeneid. But it changed the meaning of the Trojan war entirely. The past, in other words, was actively reorganised – through stories that could be reworked, extended and connected across time and space.

Turning defeat into origin

For Roman audiences, the Trojan war was more than a distant Greek legend. It became a way of thinking about origins, identity and power.

Claiming descent from Troy was more than a matter of tracing a lineage. It required constant cultural work – through storytelling, education and shared knowledge. The Iliad provided the raw material: characters, events and genealogies that could be reshaped and redeployed across generations.

Across the Roman Empire, educated elites learned Homer as part of their schooling. They quoted him in speeches, analysed him in classrooms and used him to signal cultural authority. To know the Iliad was to speak a language that others across the empire understood.

A senator in Rome, a teacher in Asia Minor or a student in Egypt could all draw on the same stories. The poem created a shared frame of reference – one that allowed very different people to situate themselves within a common past.

In the Roman imperial period, the site of ancient Troy – located in modern-day Turkey – became a destination. Emperors invested in its development, tying it directly to Rome’s claimed Trojan origins. Under Emperor Augustus, Troy was folded into the political language of empire. And under Emperor Hadrian, it became part of a wider culture of travel, memory and heritage.

A visitor to Troy in the 2nd century AD would have arrived at a curated landscape. There were baths, places to stay and spaces for performance. A small theatre – the Odeion – was built directly into the ancient citadel, so that the remains of the bronze age city, understood as the setting of the legendary battles around Troy, formed a dramatic backdrop.

Visitors could walk through what was presented as the setting of Homeric epic, experiencing the Trojan war as something anchored in the ground beneath their feet.

From Troy to Egypt

Across the Roman Empire, the Iliad circulated as a living text: copied, taught and read. Egypt, one of Rome’s most important provinces, was no exception. Yet here, Homer circulated within a cultural landscape that differed in important ways from the Greek literary world in which the poem had first taken shape.

For Roman observers, Egypt often appeared as a place where antiquity was materially preserved as well as remembered – through temples, monuments and practices that emphasised continuity with the past. At the same time, it was a deeply hybrid society, where Egyptian, Greek and Roman traditions interacted in complex ways.

Homer was among the most widely copied authors in Roman Egypt – read and taught as a marker of education and cultural belonging and deeply embedded in everyday literary culture.

The Homeric version of the Trojan War was particularly prominent among the Greek-speaking elite, especially in urban centres such as Oxyrhynchus, where the mummy was found. Other versions of the story – which placed greater emphasis on Paris and Helen’s stay in Egypt, as reported by Herodotus based on accounts from Egyptian priests – were probably more widespread among the broader Egyptian population.

The initial media coverage of the discovery of the fragment inside the Egyptian mummy suggested the text was deliberately chosen to accompany the deceased. As a personally meaningful object, perhaps reflecting their education or cultural identity.

The most telling explanation, however, may be the most straightforward. Discarded or damaged papyri could be reused as inexpensive material. The fragment may therefore have functioned as stuffing – bundled together and inserted into the body cavity without particular regard for its literary content.

The very fact that a scrap of the Iliad could end up as disposable filling, however, speaks to how deeply Homer had penetrated everyday life in Roman Egypt.

A text in motion

To make sense of the past in the Roman world meant moving between story and monument, between genealogy and deep time. Each perspective made the others more intelligible.

The Iliad helped create a world in which different pasts could be connected, compared and reshaped. By linking stories, places and traditions across the Mediterranean, the Roman world turned the past into a flexible resource – one that could generate identity, authority and belonging in shifting contexts.

This is why the Iliad mattered: it circulated across many different settings. It shaped elite education, but it was also part of everyday reading culture. At Troy, it helped transform the city into a place of cultural memory. The text itself also had a long material afterlife, surviving not only as an authoritative story, but through manuscripts and writing materials that were copied, passed on – or even reused for entirely different purposes.

Its most enduring insight is therefore this: the past is not something simply preserved, but something continuously made and remade – through the stories, practices and materials that carry it across time.

This article features references to books that have been included for editorial reasons, and may contain links to bookshop.org. If you click on one of the links and go on to buy something, The Conversation UK may earn a commission.

Stephan Blum, Research Associate, Institute for Prehistory and Early History and Medieval Archaeology, University of Tübingen and Stefan Baumann, Assistant Professor of Egyptology, KU Leuven

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

A great Tyrannosaurus rex strides through the conifer trees of her territory, sniffing the air. She picks up the scent from the carcass of a dead horned dinosaur, Triceratops, that she was feeding on yesterday. She walks over and strips off some more shreds of meat, but the smell is foul even for her.

She goes down to the lake to drink and small crocodiles and turtles scuttle into the water. But she hardly sees them. Of more interest is an armoured dinosaur, Ankylosaurus, lurking nearby. However, she knows this dinosaur won’t be an easy kill and she isn’t desperate enough for food to risk a fight. Little does she know there are bigger dangers ahead. She looks up and sees a bright light racing downwards accompanied by faint crackling and sizzling noises.

Our T. rex has excellent hearing for low frequency sounds and she is disturbed by the vibrations she can feel. But her upset only lasts for a moment. In a flash, she has been burnt to a crisp and her world changed forever.

This all happened 66 million years ago, when a huge asteroid famously hit the Earth in the area of what is now the Caribbean. At the end of the Cretaceous period, sea levels were 100–200 metres higher than today, so the shores of the Caribbean lay far inland over eastern Mexico and the southern United States. The impact happened entirely within these waters.

The event triggered instant changes to our planet and its atmosphere and led to the extinction of the dinosaurs and about half Earth’s other species. But what would it have been like to experience such a gargantuan impact? What would you have seen, heard or smelled? And how would you have died – or survived?

The Insights section is committed to high-quality longform journalism. Our editors work with academics from many different backgrounds who are tackling a wide range of societal and scientific challenges.

As experts on meteoritics and palaeontology, respectively, we’ve created a detailed timeline, based on decades of research, to take you right there. So let’s start by travelling back in time to the very last day of the Cretaceous.

T-minus one day

All is calm and the Cretaceous day proceeds as usual. In what will soon be ground zero, it is pleasantly warm, about 26°C, and wet. It often is. For about a week, the asteroid has been visible only at night. Because the giant rock is heading straight towards Earth, it looks like a motionless star. There is no dramatic tail; this is a rocky asteroid rather than a comet.

In the last 24 hours, the light becomes visible during the daytime. But it still looks like a star or planet, getting brighter in the final few hours before impact.

T equals 0: the impact

If you were close by, you would first have experienced a brief light and sound show. Minutes to seconds before the impact, you’d have seen the bright fireball, and its accompanying crackling or fizzing noises. This sizzling sound is a result of the photo-acoustic effect: the intense light of the fireball warms the ground, which then heats the air above it, causing pressure waves, or sound.

Next, a deafening sonic boom, which occurs because the asteroid is travelling faster than the speed of sound. But the asteroid is so huge, perhaps 10km in diameter, that it almost certainly hits the ground before any living creature near the impact zone has time to run for cover.

The asteroid’s enormous energy forms a crater through a series of processes that together take only a few seconds. As the asteroid collides with the surface, its kinetic (movement) energy is instantly transferred to the surface as a combination of kinetic, thermal (heat) and seismic energy (released during earthquakes). This results in a series of shock waves that heat and compress both the asteroid and its target.

As the shock waves propagate, rocks fracture, break up and are ejected, producing a bowl-shaped depression, or transient cavity, about ten seconds after impact. The heat and compression also melt and vaporise large volumes of material, including the asteroid itself, releasing a fountain of incandescent vapour (its temperature is more than 10,000 K, or 9726.85°C).

Over the next few seconds, the cavity increases in size to many times the diameter of the original asteroid. Simulations suggest that around 20 seconds after impact, the transient cavity is at least 30km deep – deeper than the deepest depth currently known on Earth, the 11km Challenger Deep valley, part of the Pacific Ocean’s Marianas Trench. The rim of the crater is over 20km high – more than twice the height of 8,900m Mount Everest.

But this enormous feature lasts for less than a minute before it starts to collapse. Within three minutes of the impact, the centre of the crater has rebounded to form a peak several kilometres high. The peak only lasts about two minutes before collapsing back into the crater.

Whether a dinosaur or a dung beetle, if you were near the transient cavity you would have been incinerated instantly by the blast. But even if you were up to 2,000km from the epicentre, you’d likely have been killed quickly by the thermal radiation and supersonic winds now spreading out from the impact site.

T-plus 5 minutes

Five minutes after the impact, the winds have “eased” to those of a category 5 hurricane, flattening everything within about 1,500km of the impact. Destroying everything, that is, which has not already been burnt. Atmospheric temperatures in the region rise to over 500K (226.85°C). This would feel like being inside an oven – causing burns, heatstroke and death. Wood and plant matter ignite, creating fires everywhere.

Because the asteroid struck the sea, the atmosphere is also filled with super-heated steam, making the hurricane-force winds even deadlier.

Next come the tidal waves, triggered by the vast quantities of displaced rock and water. These 100-metre megatsunamis first strike the shores of what is now the Gulf of Mexico, engulfing the land before depositing huge amounts of debris as they retreat.

By now, the crater has almost reached its final dimensions – 180km across and 20km deep. But making an enormous hole in the ground isn’t the only outcome of the impact. All the rock and vapour displaced during the collision has to go somewhere. Several locations in Northern America show that metre-sized blocks of debris from the impact were thrown distances of hundreds of kilometres.

So if you were 2,000km to 3,000km from the epicentre and survived the first few seconds, you’d most likely die from overheating, earthquakes, hurricanes, fires, tsunami-driven floods or being hit by impact melt.

But what is happening much further away? In the first five minutes after impact, dinosaurs roaming the Cretaceous forests of what are now China or New Zealand are so far undisturbed.

But it won’t be long before that changes.

T-plus one hour

Shockwaves on land and sea are only minor inconveniences compared with the fire that is still radiating down from the sky. Some of the impact energy has been transferred into the atmosphere, heating the air and dust to incandescence.

An hour after impact, a belt of dust has circled the globe. Deposits of solidified molten droplets (impact spherules) and mineral grains have been found in numerous locations from New Zealand in the south to Denmark in the north. In these locations, you would not have been aware of the tsunamis around the Americas or the wildfires, but the skies would certainly have begun to darken.

T-plus one day

By now, huge tsunamis are moving east across the Atlantic and west across the Pacific, entering the Indian Ocean from both sides.

They are still around 50m high – causing death and destruction across many coasts around the world. By comparison, the 2004 Boxing Day tsunami reached heights of up to 30 metres. Tsunamis kill fishes and marine life that are washed high on the shore and then dumped, just as they kill coastal trees and drown land animals. But the tsunamis gradually fade away and probably don’t wipe out any entire species – at least on their own.

The hurricane force winds have also died down, but tropical storm strength winds are whipping up debris and causing further chaos and destruction across the tsunami-affected areas. The burning sky is also triggering wildfires across the globe – which, in turn, carry ever more soot into the atmosphere. The sooty signature of these wildfires has been found deposited as carbon particles in sediments from the K-Pg boundary – a 66-million-year-old thin clay layer.

Further away, in what is modern Europe and Asia, the skies continue to fill up with dust and soot, as they do everywhere. Temperatures start to drop as sunlight is blocked. Trees and plants in general, including phytoplankton, close down as if for winter, unable to photosynthesise. Any animals that rely on warm conditions ultimately hunker down and die.

T-plus one week

It’s getting darker and darker. Simulations of solar radiation reaching the Earth’s surface following the impact indicate that, after about a week, the solar flux (the amount of heat and light per a certain area) is just one thousandth of that prior to the impact. This is caused by particles of dust and soot in the atmosphere.

The continued decrease in light levels is accompanied by a global drop in surface temperatures of at least 5°C. This means that most of the dinosaurs and other large flying and swimming reptiles probably die from freezing within the course of this first week (smaller reptiles with slower metabolisms or more flexible diets could survive longer). Cooling temperatures and cloud cover also lead to rain. But not just any rain. Storms of acid rain fall across the Earth.

Two separate mechanisms generate acid rain. The first is down to the geology of the impact region. The asteroid happened to hit an area of sediments rich in sulphur, which vaporised and caused sulphur oxides (acidic and pungent gas compounds composed of sulphur and oxygen) to be part of the plume of plasma blasted into the atmosphere. Second, the energy of the collision was sufficient to turn nitrogen and oxygen into nitrogen oxides – highly reactive gases that can form smog.

The dropping temperature ultimately allows water vapour to condense into drops, and the sulphur and nitrogen oxides dissolve to form sulphuric and nitric acids. This is sufficient to generate a rapid drop in pH. Early models suggest that the pH of the rain might be as low as 1 – the same acidity as battery acid.

At this point, Earth is not a great place to be. Rotting vegetation, choking smoke and sulphur aerosols combine to make the planet stink. Plants and animals on land and in shallow seas that have survived the darkness and cold succumb to the corrosive acid rain and ocean acidification. Acid rain also kills trees by leaching nutrients such as calcium, magnesium and potassium from the soil. Shallow marine shellfish, crustaceans and corals also die as acid seawater destroys their skeletons.

T-plus one year

Winds die down, wildfires are extinguished and the oceans are once again calm. It might appear that the asteroid collision is just a scar on the ocean floor. But its effects are still destructive. The atmosphere is still filled with dust and the Sun hasn’t shone for a year. Temperatures have continued to drop, with the average surface temperature now 15°C lower than before the impact. Winter has come.

Any dinosaurs or marine reptiles that survived the first week of freezing conditions would have died very soon after. A year after the impact, only rotted skeletons of these behemoths remain. Here and there, smaller animals like mammals the size of rats and insects would be nestling in crevices, barely surviving on their reserves and decaying plants.

Indeed, it has not been a good year for life on Earth: over 50% of plants have died out because of the cold and lack of sunlight. And similar losses have occurred among terrestrial animals and species in the acidified, shallow sea waters.

While most plant groups and many of the modern groups of insects, fishes, reptiles, birds and mammals recover reasonably rapidly, things don’t look great for other species. Dinosaurs and pterosaurs living on land are extinct, as are many marine reptiles, ammonites, belemnites and rudist bivalves in the oceans. Ammonites and belemnites are high in their food chains, and so suffer not only from the cold and acidification but also from the loss of abundant food resources, such as smaller marine organisms.

T-plus ten years

The Earth is still in the grip of a fierce winter. Although most of the sulphur has rained out of the atmosphere, dust and soot particles remain. The average surface temperature is still about 5°C lower than before the impact. The main oceans have not frozen, but inland lakes and rivers around the world are iced over.

Clearly, there were no humans about at this time – there weren’t even any larger mammals. But given the only species that survived were those that could burrow or live below water, it is unlikely that you could have survived this long.

Surviving plant and animal groups such as turtles, smaller crocodiles, lizards, snakes, some ground-dwelling birds and small mammals repopulate the Earth at this point. But they are forced back to limited areas of relative safety a long way from the impact site. These areas are now receiving sufficient sunlight for plants and phytoplankton to photosynthesise again. As leaves and seeds provide the basis for the food chains on land and in the sea, life begins to rebuild.

Eventually, life returns to the devastated landscapes, but ecosystems are very different and the dinosaurs are no more.

T-plus 66 million years

Today, 66 million years after the impact, the scars of the collision are hidden within geological strata – and scientists have started deciphering them. It was in 1980 that researchers first reported evidence of the impact. In their classic paper, Luis Alvarez, a Nobel-prize-winning physicist, and co-authors, described a sudden enrichment in the element iridium in a specific clay layer in Denmark and in Italy.

Iridium is rare in surface rocks because most of it was sequestered in Earth’s core when the planet first formed. However, iridium is found in meteorites, and Alvarez and colleagues inferred that the rate of accumulation of the metal in the sediments was so high that it could only have been produced by impact of a gigantic meteorite.

Because the scientists had only observed the iridium spike in two locations, the impact hypothesis was rejected by many scientists at the time. However, through the 1980s, iridium spikes were identified in clay layers at more and more locations – in muds laid down on land, in lakes, in the sea.

Support for an impact hypothesis strengthened when a crater of the correct age was found in 1991. The crater is buried beneath younger rocks, but clearly visible in geophysical surveys, lying half on land in the Yucatán Peninsula of Mexico, and half offshore. Since 1990, evidence for the impact has increased, not least when scientists discovered that there was indeed a sharp cooling event at the end of the Cretaceous.

In total, it is estimated that half the species of plants and animals alive at the end of the Cretaceous disappeared. It was once thought that surviving groups such as many plants, insects, molluscs, lizards, birds and mammals somehow escaped unscathed. But detailed study shows that this is not the case – they were all hit hard.

But, by chance or luck, enough individuals and species were able to survive the cold and absence of food, or were in parts of the world where the effects were less extreme. As the world returned to normal, they had the opportunity to expand rapidly into their old niches, but also to occupy the space vacated by extinct groups. In fact, one important consequence of the extinction of the dinosaurs, apex predators in their heyday, was the successful spread and evolution of mammals.

When Alvarez and colleagues first described the drop in temperature following the impact, they called it a “nuclear winter”, reflecting the political climate of the early 1980s. Now we might be more inclined to describe the effects as a global climate change – similar events are currently resulting from increased carbon dioxide in the atmosphere (flooding, temperature fluctuations).

It is salutary to think that without the asteroid collision, primates might never have reached the level we are at today. But it is equally salutary to consider that modern humans are causing some of the same changes to the atmosphere that ultimately killed our reptilian forbears and may one day also lead to our own demise.

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Michael J. Benton, Professor of Vertebrate Palaeontology, University of Bristol and Monica Grady, Professor of Planetary and Space Sciences, The Open University

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