Skip to story
ELI5 Yahaaa

Topic

Light & colour

Shining, bending, bouncing, and every colour — 68 tiny stories from every shelf.

Sky on fire, quietly

What Are the Northern Lights?

Particles from the Sun crash into high air and make it glow like a neon sign.

Let’s go →

Gravity turned all the way up

What Is a Black Hole?

A black hole is matter packed so tightly that light cannot escape its pull.

Let’s go →

Join the dots

What Are Constellations?

Constellations are shapes we drew on the sky — the stars are not really grouped.

Let’s go →

A very old puzzle

Why Is the Night Sky Dark?

The night sky is dark because the universe is young and still expanding.

Let’s go →

More time in the light

Why Are Days Longer in Summer?

Summer days are longer because your half of Earth leans into the sunlight.

Let’s go →

A spinning Earth story

Why Day Turns Into Night

Night is simply your side of Earth turned away from the Sun.

Let’s go →

Three things in a line

What Happens in an Eclipse?

An eclipse is one space rock's shadow landing on another.

Let’s go →

Watching for a tiny dip

How Do We Find Planets Around Other Stars?

Most exoplanets are found by the tiny repeating dip in starlight as the planet passes in front.

Let’s go →

A distance, not a time

What Is a Light Year?

A light year is a distance — how far light travels in twelve months.

Let’s go →

A rusty planet

Why Is Mars Red?

Mars looks red because its dust is literally rusted iron.

Let’s go →

You live inside it

What Is the Milky Way?

The Milky Way is our galaxy — and we see it as a band because we are inside it.

Let’s go →

It was never a night object

Why Can You See the Moon in Daytime?

The Moon is often up in daytime, and you can see it whenever it is bright enough to beat the blue sky.

Let’s go →

Too far away to fall behind

Why Does the Moon Follow the Car?

The Moon appears to follow you because it is far too distant for your travel to shift its direction at all.

Let’s go →

Same ball, different view

Why the Moon Changes Shape

Half the Moon is always lit — phases are how much of that half faces you.

Let’s go →

A star nursery

What Is a Nebula?

Nebulae are giant space clouds where stars are born and where they die.

Let’s go →

The air is doing it

Why Do Stars Twinkle but Planets Do Not?

Twinkling happens in our atmosphere, not in the star, and planets are too broad for it to show.

Let’s go →

A night-sky flicker

Why Stars Twinkle

Moving air bends starlight on its way down, so the star seems to flicker.

Let’s go →

A bigger eye

How Do Telescopes Work?

Telescopes gather far more light than your eye and focus it to a point.

Let’s go →

Light, sorted

Where Do Colours Come From?

Colour is which parts of white light an object bounces back at your eyes.

Let’s go →

Bouncing all the way

How Does Light Go Round a Bend?

Light travels round bends in a fibre by reflecting off the inside walls thousands of times a metre.

Let’s go →

Light marching in step

What Makes a Laser Different From a Torch?

A laser differs from a torch because its light is one colour, one direction, and every wave in step.

Let’s go →

Bending light on purpose

How Do Lenses Work?

A lens bends light because its curved shape slows different parts of a beam by different amounts.

Let’s go →

A very smooth wall

How Do Mirrors Work?

Mirrors work because their surface is smooth enough to bounce light without scrambling it.

Let’s go →

Same family, different size

Is Radio Really a Kind of Light?

Radio is genuinely light, just with waves metres long instead of fractions of a millimetre.

Let’s go →

Light coming back

Why Can You See Yourself?

Reflection is light bouncing off a surface at the same angle it arrived.

Let’s go →

Light changing lanes

Why Does a Straw Look Bent?

A straw looks broken because light bends when it leaves water and enters air.

Let’s go →

Light in a straight line

Why Do Shadows Happen?

A shadow is the place light could not reach because something was in the way.

Let’s go →

Sun overhead

Why Are Shadows Short at Noon?

Shadow length depends on how high the Sun is — highest at noon, so shortest then.

Let’s go →

Making a colour hold on

How Does Colour Stay in Cloth?

A dye colours cloth by bonding to the fibres themselves, rather than sitting on the surface like paint.

Let’s go →

The metal that will not change

Why Is Gold So Special?

Gold is prized because it never corrodes, is easy to shape, and is genuinely rare — and it was made in exploding stars.

Let’s go →

Some colour dissolves, some just sits there

Why Does Ink Stay on the Paper?

Ink is colour carried in a liquid that then leaves, either soaking into the fibres or drying on top of them.

Let’s go →

Three jobs in one tin

What Is Paint Made Of?

Paint is coloured powder held in a glue and thinned with a liquid that leaves once it is on the wall.

Let’s go →

Light finds nothing to grab

Why Can You See Through Glass?

Light goes through glass because there is nothing in it that can absorb visible light, and nothing inside to scatter it.

Let’s go →

A shared pool of electrons

Why Is Metal Shiny?

Metal shines because its outer electrons are shared loosely by every atom, and that sea throws light back.

Let’s go →

Light getting bounced

Why Is the Sky Blue?

Air scatters blue light sideways, so it reaches your eyes from everywhere.

Let’s go →

Raindrops as prisms

How Does a Rainbow Work?

Raindrops bend and reflect sunlight, splitting it into a curved band of colour.

Let’s go →

An old rhyme, half right

Does a Red Sky Really Predict the Weather?

A red sunset means clear dry air to the west, which in Britain is tomorrow's weather.

Let’s go →

Water eats red light

Why Is the Sea Blue?

The sea looks blue because water absorbs red light quickly and only blue makes it back to your eyes.

Let’s go →

Ice with air in it

Why Is Snow White and Fluffy?

Snowflakes are ice crystals, and snow looks white because of countless surfaces bouncing light.

Let’s go →

Light not getting through

Why Do Storm Clouds Look Dark?

Storm clouds look dark because they are thick enough to stop light reaching you.

Let’s go →

Light taking the long way

Why Are Sunsets Orange?

At sunset light travels through much more air, which strips out the blue.

Let’s go →

A planned demolition

Why Do Leaves Change Colour?

Trees break down their green pigment and cut leaves loose before winter, revealing the colours underneath.

Let’s go →

Watching blood being cleared up

Why Does a Bruise Change Colour?

A bruise changes colour because the spilled blood is dismantled in stages, and each stage is a different colour.

Let’s go →

The colour it refuses

Why Are Leaves Green?

Leaves are green because chlorophyll absorbs red and blue and reflects green.

Let’s go →

Moving the focus point

How Do Glasses Help You See?

Glasses pre-bend light so the image lands exactly on the back of your eye.

Let’s go →

Building food from air

How Do Plants Eat Light?

Plants use sunlight to build sugar out of air and water.

Let’s go →

Light in, picture built

How Do Your Eyes See?

Eyes convert light into nerve signals, and the brain builds the image.

Let’s go →

More than a wrapper

What Does Your Skin Do?

Skin keeps things out, controls temperature, senses the world and repairs itself.

Let’s go →

Breaking up the outline

How Does Camouflage Work?

Camouflage works by breaking up an animal's outline so no shape is recognised.

Let’s go →

Sticky feet and a very fast eye

How Does a Fly Walk on the Ceiling?

A fly sticks to ceilings with clawed, glue-footed pads, sees the world far faster than you do, and tastes with its feet.

Let’s go →

A very old rule, badly broken

Why Do Moths Fly Into Lights?

Moths navigate by keeping a distant light at a fixed angle — a rule that works with the moon and fails badly with a lamp.

Let’s go →

A whole second shift

Why Do Some Animals Only Come Out at Night?

Night-living animals avoid heat, hide from daytime hunters, and get the food that daytime animals leave alone.

Let’s go →

Skin that works like a screen

How Does an Octopus Change Colour?

An octopus changes colour with millions of tiny colour bags in its skin, squeezed open and shut by muscle.

Let’s go →

Hearing in three dimensions

How Do Owls Hunt in the Dark?

Owls hunt by sound, using lopsided ears to pinpoint prey in total darkness.

Let’s go →

Every mix absorbs more

Why Does Mixing Paint Make Brown?

Mixed paints absorb more and more light, so the result heads towards brown.

Let’s go →

Colours bending differently

What Does a Prism Do?

A prism splits white light into colours because each colour bends differently.

Let’s go →

Blocking light, close and far

How Do Shadow Puppets Work?

Shadow puppets work because blocked light spreads out, so nearer objects cast bigger shadows.

Let’s go →

Light bouncing off two surfaces

Why Are Soap Bubbles Colourful?

Bubble colours come from light reflecting off both surfaces of the film and interfering.

Let’s go →

A shadow swinging with the sky

How Does a Sundial Tell Time?

A sundial works because Earth's rotation swings the Sun's shadow steadily around.

Let’s go →

Wide, narrow, wide

How Does a Shop Scanner Read a Barcode?

A barcode is a number written as stripes, and the scanner reads it by measuring reflected light as it sweeps across.

Let’s go →

Counting light in tiny buckets

How Does a Photo Get Caught?

A photo is a count of light: a lens focuses it, a shutter times it, and a grid of wells measures it.

Let’s go →

A wire too hot to stay dark

How Does Electricity Become Light?

An old bulb glows because a thin wire resists the current and gets white-hot; an LED makes light directly.

Let’s go →

Dots, fired one at a time

How Does a Printer Place Ink So Exactly?

A printer breaks a page into a grid of dots and fires a tiny drop of ink at each one as the head sweeps across.

Let’s go →

A light you cannot see

How Does a Remote Control Reach the Television?

A remote control blinks an invisible infrared light in a pattern, and the television has a sensor that reads it.

Let’s go →

Millions of tiny lights

Why Are Pictures Made of Dots?

Screens show pictures as a grid of dots mixing red, green and blue, redrawn fast enough to look like motion.

Let’s go →

Light knocking electrons loose

How Does Sunlight Become Electricity?

A solar panel works because packets of light knock electrons loose and the cell's layers send them all the same way.

Let’s go →

Three colours, several million times

How Does a Television Make a Picture?

A television makes pictures out of millions of tiny red, green and blue lights, each given a brightness many times a second.

Let’s go →

Radio you cannot hear

How Does the Internet Cross a Room?

Wifi is radio: data rides on a wave that is wobbled in a pattern your phone knows how to read back.

Let’s go →