Explain like I’m 5
Big pictures.
Few words.
Tiny true stories about space, math, and everyday wonders — told with bright SVG pictures.
Space
Crashy night-sky stories
All space →Too far away to fall behind
Why Does the Moon Follow the Car?
A hedge sweeps past in a second and a far hill barely stirs. The Sun, the planets and every star hold their place on a journey for the same reason.
Let’s go →Gravity turned all the way up
What Is a Black Hole?
Pack matter tightly enough and escaping it would mean travelling faster than light. Nothing can, so nothing leaves — not even the light itself.
Let’s go →Sky on fire, quietly
What Are the Northern Lights?
Earth's magnetic field turns the solar wind aside but funnels some of it down at the poles, where it lights up atoms 100 km overhead like a neon sign.
Let’s go →A definition, not a demotion
Why Is Pluto Not a Planet Any More?
Finding Eris, heavier than Pluto, forced a choice: name a tenth planet or redraw the line. Pluto now leads a category instead of trailing one.
Let’s go →The strangest calendar
A Day on Mercury Lasts Longer Than Its Year
It laps the Sun in 88 days but takes 176 to get from one sunrise to the next, and radar has found ice in craters the sunlight never reaches.
Let’s go →You would not notice for eight minutes
What If the Sun Went Out Tonight?
The light takes eight minutes and twenty seconds to arrive, and so would the news — after which the freeze takes days rather than seconds.
Let’s go →Physics
Invisible forces you can play with
All physics →Not the chair, not this page
You Have Never Touched Anything
Solid contact is a force, not a meeting — the outer electrons of two surfaces repel each other hard enough that nothing ever quite arrives.
Let’s go →A skin made of pulling
Why Does a Paperclip Float on Water?
Water molecules cling to one another so strongly that the surface behaves like a stretched skin, and a paperclip simply rests in the dent.
Let’s go →Waves bunched and stretched
Why Does a Siren Change Pitch as It Passes?
To the driver the siren never changes at all. Light does the same thing, which is how a receding galaxy shifts red and betrays an expanding universe.
Let’s go →Light changing lanes
Why Does a Straw Look Bent?
Light changes speed crossing from water into air, and changing speed at an angle makes it turn. Your brain assumes straight lines and misplaces the straw.
Let’s go →About a hundred watts of it
You Are Glowing Right Now
Warm objects radiate light whose colour depends on their temperature — yours is infrared, invisible to us and perfectly obvious to the right camera.
Let’s go →You could not start, either
What If Friction Stopped for One Minute?
Everyone expects to slide. Almost nobody expects to be unable to start, hold, stand, or keep a single screw or knot from letting go.
Let’s go →What things are made of
Atoms, metal, glass, plastic, and every kind of stuff
All what things are made of →Glowing gas, not glowing wood
What Actually Is a Flame?
A flame is not the wood burning. It is gas driven out of the wood by heat, glowing as it meets oxygen — which is why heat, air or fuel each put it out.
Let’s go →The same atom, two arrangements
Why Is Diamond Hard and Pencil Lead Soft?
The grey line a pencil leaves is stacks of carbon sheets sheared off onto the paper — the very same atoms that let diamond scratch everything.
Let’s go →Three thousand years, unspoiled
Honey Found in a Tomb Is Still Honey
Honey does not spoil, because three defences work at once — almost no free water, unexpected acidity, and an enzyme the bees add that makes peroxide.
Let’s go →A chemical that lies to your nerves
Why Are Some Peppers Hot?
A chilli is not actually hot. It carries a chemical that opens the nerve reporting high temperature, so the burn is a signal about nothing.
Let’s go →99.8 per cent nothing
The Solid That Is Almost Entirely Air
Aerogel is a gel with the liquid removed and the solid skeleton left standing — a feat of drying rather than chemistry, and the best insulator we can make.
Let’s go →Light finds nothing to grab
Why Can You See Through Glass?
Glass electrons can only absorb one exact size of bite and visible light is too small, so a window stops sunburn but never the view.
Let’s go →Math
Number ideas with toys
All math →Every circle's hidden number
What Is Pi and Why Does It Never End?
Fifteen decimal places would size a circle as wide as the solar system to within a finger's width, which is rather more than anyone has ever needed.
Let’s go →Never running out
What Is Infinity?
Infinity is not a huge number — it is the fact that counting never has to stop. Infinitely many fractions fit between 0 and 1, with room to spare.
Let’s go →A 50.7 per cent chance
In a Room of Twenty-Three, Two People Share a Birthday
With 23 people the odds of a shared birthday pass one half, because 23 people make 253 pairs — and it is the pairs, not the people, that get the chances.
Let’s go →A number your eye reads first
Why Does Everything Cost £4.99?
People read the leftmost digit first and round the rest away, so a price of 4.99 gets quietly filed in memory as four. Shops have known this for a century.
Let’s go →You are usually in the slow one
Why Is the Other Queue Always Faster?
With three tills, two queues are beating yours most of the time. One shared queue feeding every till makes the wait both fairer and shorter.
Let’s go →Proved in 1976, by machine
Four Colours Are Always Enough
Four colours suffice for every possible map — a claim that resisted proof for over a century, then fell to a computer checking 1,936 cases no human could.
Let’s go →Earth & sky
Weather, light, and the air around us
All earth & sky →Light getting bounced
Why Is the Sky Blue?
Air molecules knock short blue waves sideways about ten times more readily than red ones, so blue arrives at your eyes from every patch of sky at once.
Let’s go →Raindrops as prisms
How Does a Rainbow Work?
Every raindrop bends sunlight, splits it and throws it back at a fixed 42-degree angle. The bow is a circle drawn on the sky opposite the Sun.
Let’s go →Pressure finding a way out
Why Do Volcanoes Erupt?
Molten rock is lighter than the rock above it, so it rises. Dissolved gas expanding on the way up is what turns that rise into an eruption.
Let’s go →A spin tipped upright
How Does a Tornado Form?
Winds at different heights roll the air into an invisible horizontal tube. A storm's updraught tips that tube upright and stretches it until it spins hard.
Let’s go →The Moon pulling
Why Does the Sea Go In and Out?
The Moon pulls the ocean into two bulges on opposite sides of the planet, and Earth turns through both, which is why high tide comes round twice a day.
Let’s go →A bump of one part in seven hundred
Shrink Earth to a Marble and You Could Not Feel Everest
The tallest mountain on Earth is a rounding error against the planet's radius, which is why a scale model of Earth would feel smooth in your hand.
Let’s go →Life & body
Seeds, hearts, senses, and growing things
All life & body →A brain rehearsing offline
Why Do We Dream?
In one stage of sleep the brain replays and files the day while the body is locked still and the fact-checking parts are turned right down.
Let’s go →Roughly one bacterium per human cell
About Half of You Is Not You
Your body is roughly half bacteria by cell count, mostly living in your gut, and the famous ten-to-one version of that figure turned out to be wrong.
Let’s go →Drowning out one signal with another
Why Does Scratching Feel So Good?
Your liver can hurt but it cannot itch, because there are no itch fibres below the surface. And scratching releases chemicals that bring it back.
Let’s go →A planned demolition
Why Do Leaves Change Colour?
A tree times it by the length of the night, so a warm autumn still turns on schedule. The leaf never falls, either: a layer of cells forms and lets go.
Let’s go →Light in, picture built
How Do Your Eyes See?
Eyes turn light into nerve signals. The picture you see is assembled afterwards by the brain — patched, corrected, and rather less direct than it feels.
Let’s go →Blasting the nose clear
Why Do We Sneeze?
A sneeze is a reflex, not a decision: irritated nerves in your nose trigger a blast of air fast enough to clear them — and to spread germs remarkably well.
Let’s go →Animals
Creatures on land, in the sea, and in the air
All animals →The oldest argument in the field
Why Do Zebras Have Stripes?
People argued about zebra stripes for a hundred and fifty years. The best answer involves biting flies, not lions — plus blurring the herd.
Let’s go →Turning round in mid-air
Why Does a Cat Always Land on Its Feet?
A falling cat has nothing to push against, and turns over anyway: it tucks one end in and leaves the other out, then swaps, twisting each half in turn.
Let’s go →Rebuilt from the inside
How Does a Caterpillar Become a Butterfly?
Inside the chrysalis the caterpillar dissolves into a soup of cells, and clusters that have waited since it hatched build a butterfly out of the wreckage.
Let’s go →And it stops one of them to swim
An Octopus Has Three Hearts and Blue Blood
An octopus runs on copper-based haemocyanin rather than iron-based haemoglobin: blue, good in cold water, and inefficient enough to need three hearts.
Let’s go →Four layers and a good idea
How Do Penguins Stay Warm in the Snow?
An emperor penguin stands through months of the coldest dark on Earth without eating, on trapped air, fat, cold feet and a rotating huddle.
Let’s go →By about sixty million years
Sharks Are Older Than Trees
Sharks appear in the fossil record 65 million years before the first true trees — and they are older than Saturn's rings and older than the North Star.
Let’s go →Everyday wonders
Kitchen, bubbles, echoes, and odd little magic
All everyday wonders →Steam bursting out
Why Does Popcorn Pop?
A kernel is a waterproof shell with water sealed inside. Heat turns that water to high-pressure steam until the shell can no longer hold it in.
Let’s go →Your brain saw it coming
Why Can't You Tickle Yourself?
A machine that copies your own hand movement half a second late really does tickle you, because the prediction your brain made no longer lines up.
Let’s go →A liquid that panics
Why Can You Run on Cornflour and Water?
Shove the grains together faster than the water between them can escape and they jam like a solid. Stop pushing and the mixture is a liquid again.
Let’s go →Light bouncing off two surfaces
Why Are Soap Bubbles Colourful?
No pigment is involved. Light reflects off both sides of a film a thousandth of a millimetre thick, and a different colour cancels at each thickness.
Let’s go →Faster sound, same vibration
Why Does Helium Make Your Voice Squeaky?
Sound travels far faster in helium, so the resonances of your unchanged throat leap upward. Your vocal cords carry on buzzing at exactly the same pitch.
Let’s go →An honestly unfinished answer
Hot Water Sometimes Freezes First, and Nobody Is Sure Why
The Mpemba effect — hot water sometimes freezing before cold — keeps being reported, keeps being disputed, and after two thousand years is unexplained.
Let’s go →How things work
Everyday machines, taken apart
All how things work →Radio you cannot hear
How Does the Internet Cross a Room?
Wifi is radio. Your data rides on a wave wobbled in a pattern both ends agreed to read, and every device sharing that channel waits its turn.
Let’s go →A siphon, not a plug
Why Does a Toilet Flush by Itself?
A toilet flushes because a sudden rush of water fills the bend behind the bowl, and a full bend pulls the rest away by itself.
Let’s go →Under the floor and back
Where Do Escalator Steps Go at the Top?
The steps never end. Two guide tracks at changing spacings make them form stairs in the middle and flatten at both ends, then return underneath.
Let’s go →A wave made of cars
Why Is There Nothing at the Front of a Traffic Jam?
Most traffic jams have nothing at the front: one small braking spreads backwards down the line as a wave and never quite fades out.
Let’s go →Carrying heat out, not cold in
How Does a Box Make Itself Cold?
There is no such substance as cold. A fridge squeezes a gas hot to dump heat out behind it, then lets it expand cold to soak up some more.
Let’s go →And that is the boring half
Your Phone Beats the Computer That Flew to the Moon
The computer that landed Apollo 11 had less memory than one photo, and it was enough — because it did one job perfectly rather than everything adequately.
Let’s go →