Space
47 explanations and counting.
Why the USA and Soviet Union Raced to Space
During the Cold War, the USA and Soviet Union competed fiercely to reach space first, driven by pride, fear, and the desire to prove their system was superior.
How Big Is the Universe and What Else Is Out There?
The universe is unimaginably vast, containing billions of galaxies with trillions of stars, and scientists are still discovering what might exist beyond what we can see.
What Is In Our Solar System And How Did It Form
Discover what makes up our solar system, from the Sun and planets to asteroids and comets, and learn how it all came together billions of years ago.
Why Planets Orbit the Sun
Planets orbit the Sun because of gravity—an invisible force that pulls objects toward each other and keeps everything in the solar system moving in stable paths.
Why Do Cities Struggle When They Get Too Big
Cities face major challenges like traffic, pollution, housing shortages and overcrowding as their populations grow larger.
What Stars Are Made of and How Far Away
Stars are giant balls of hot gas held together by gravity, mostly made of hydrogen and helium, and they're so far away their distances are measured in light-years.
Planets and how they orbit the Sun
Learn what planets are, why they orbit the Sun, and how gravity keeps our solar system working.
Using Coordinates to Find Locations Anywhere
Learn how coordinates work as a universal system for pinpointing exact locations on maps, grids, and Earth itself.
Latitude and Longitude: Earth's Address System
Latitude and longitude are imaginary lines that crisscross the Earth, helping us pinpoint the exact location of any place on our planet.
Why the Moon Changes Shape Every Night
The Moon looks different shapes because of how the Sun lights it up as it orbits Earth.
The Solar System and Its Eight Orbiting Planets
Discover what the solar system is, how it formed, and learn about the eight planets that orbit our Sun.
Why do we have day and night?
Day and night happen because Earth spins on its axis, making different parts face towards and away from the Sun.
What happens when two black holes collide?
When two black holes crash into each other, they create ripples in space itself that we can detect billions of years later.
How do we know how old the universe is?
Scientists can work out the universe's age by measuring how fast galaxies are moving away from us—like cosmic detective work with a 13.8 billion year answer.
What is gravitational lensing?
Massive objects in space bend light like a cosmic magnifying glass, letting us see galaxies that would otherwise be invisible.
What is the Oort Cloud?
There's a giant invisible bubble of icy rocks surrounding our entire solar system, and it's where the most spectacular comets come from.
What is a dwarf planet?
Dwarf planets are like the forgotten middle siblings of our solar system — too big to be asteroids, but not quite big enough to be proper planets.
How did the Moon form?
The Moon was born from a cosmic crash so violent it melted our entire planet and flung molten rock into space.
What is antimatter?
Antimatter is like the evil twin of regular matter — when they meet, they destroy each other in the most explosive way possible.
What are nebulae?
These cosmic clouds of gas and dust are star nurseries, star graveyards, and some of the most beautiful sights in the universe.
What is the solar wind?
The Sun blasts invisible particles into space at a million miles per hour, creating a cosmic breeze that shapes our entire solar system.
What is a pulsar?
Imagine a lighthouse spinning so fast it flashes 700 times per second — that's basically what pulsars are, except they're dead stars in space.
What is the Kuiper Belt?
Beyond Neptune's orbit lies a vast ring of icy objects — and it's probably where most comets come from.
Could we ever travel to another star?
The nearest star is so far away that our fastest rockets would take 70,000 years to reach it — but scientists have ideas.
What is space debris?
Earth is surrounded by a cloud of broken satellites and rocket parts — and it's becoming a serious problem for space travel.
What is the Milky Way?
That faint band of light stretching across the night sky is actually our home — a galaxy of 200 billion stars we're living inside.
What is a supernova?
When a massive star dies, it doesn't go quietly — it explodes with more energy than the sun will produce in its entire lifetime.
What is an asteroid?
Asteroids are lumps of rock and metal left over from the birth of the Solar System. Most orbit quietly between Mars and Jupiter — but some cross Earth's path, and we're now learning how to deal with them.
What is a space station?
A space station is a home in orbit — a place where astronauts live and work hundreds of kilometres above Earth, moving so fast they see 16 sunrises every single day.
How does the James Webb Space Telescope work?
Webb can see galaxies that formed just a few hundred million years after the Big Bang. It does this by catching light that has been travelling for nearly 14 billion years — here's how.
What is the cosmic web?
Zoom out far enough from Earth and the universe stops looking like empty space — it looks like a giant spiderweb made of galaxies. Here's what that actually is.
Why are astronauts weightless in space?
Astronauts float around the space station — but Earth's gravity is nearly as strong up there as on the ground. So what's actually happening?
What is a neutron star?
When a star dies in a supernova explosion, sometimes what's left is an object the size of a city but more massive than the Sun — where a teaspoon of material would weigh a billion tonnes.
What is the International Space Station?
A football-pitch-sized laboratory has been continuously inhabited in orbit since 2000. Here's what happens up there — and how it stays in the sky.
What are galaxies?
Our Sun is just one of 100–400 billion stars in the Milky Way. And the Milky Way is just one of roughly 2 trillion galaxies. Here's what they are and how they form.
How do rockets work?
Getting to space requires escaping Earth's gravity with nothing but controlled explosions. Here's the physics of how rockets actually work.
What is dark matter?
About 27% of the universe is made of something that doesn't emit light, doesn't absorb light, and can't be directly detected. We know it's there — but not what it is.
What are exoplanets?
Until 1992, we only knew of planets in our own Solar System. Since then, we've found thousands of worlds orbiting other stars — and some look very familiar.
How is a star born?
Stars don't just appear. They form over millions of years in vast clouds of gas and dust — and the process is one of the most dramatic in the universe.
What is a comet?
Comets are ancient, dirty snowballs left over from the formation of the Solar System — and when they get close to the Sun, they put on one of nature's finest shows.
Could humans live on Mars?
Mars is the most Earth-like planet in the Solar System. But "most Earth-like" still means freezing, airless, and bombarded with radiation. Could we live there anyway?
What is a solar eclipse?
The Moon is 400 times smaller than the Sun but also 400 times closer. This coincidence produces one of the most spectacular events visible from Earth.
What would happen if the Sun disappeared?
The Sun is 149 million km away. It drives our weather, feeds all life, and holds the Solar System together. What would happen without it?
How big is the universe?
The universe is so big that the numbers stop making any kind of intuitive sense very quickly. Let's try anyway.
Why does the Moon affect the tides?
Twice a day, the ocean rises and falls by several metres — and it's all because of a rock 384,000 km away. Here's the physics.
What is the Big Bang?
The entire universe — every star, planet, galaxy, and atom in existence — began about 13.8 billion years ago in a single, almost incomprehensible moment.
What is a black hole?
A place in space where gravity is so strong that not even light can escape. Yes, really.