Why does it get dark in the evening?
Earth turns. The side facing the Sun has day; the other has night.
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Earth & Space
Curious questions about our planet and the sky.
Prehistory & Natural Wonders
Dinosaurs, mammoths, trace fossils, crystals and limestone caves: five learning pages with explanatory pictures.
Explore Prehistory & Natural Wonders →Sun, Moon & stars
Why does the Moon sometimes look like a banana?
The Moon remains a ball. The Sun lights roughly half of it.
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Who are Earth’s planetary neighbours?
Eight planets orbit our Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Earth is third from the Sun.
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What is a shooting star?
A shooting star is a streak of light when small space material enters Earth's air at high speed. Air and material become intensely hot.
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What is a solar eclipse?
During a solar eclipse, the Moon stands between Sun and Earth. Its shadow reaches part of Earth.
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Why do stars twinkle?
Starlight passes through the air above us. Moving layers of air bend it in changing ways, making a distant star seem to twinkle.
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Why do we mostly see the same side of the Moon?
The Moon turns once on its axis while completing one trip around Earth. Both take about the same time.
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What is a constellation?
People imagine lines between stars to make named patterns. The stars appear close together in the sky, but can lie at very different distances.
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Why does Saturn have rings?
Countless icy pieces and other particles orbit Saturn to form its rings. They are not a solid disc.
Open learning page →Space travel & gravity
Why do people float in a space station?
The station, people and objects fall around Earth together. Because they fall together, they do not press on each other as on the ground and appear weightless.
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What is a spacesuit for?
A spacesuit provides oxygen and suitable pressure outside a spacecraft. It also protects against large temperature differences.
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How can a rocket move in empty space?
A rocket throws gas backwards at high speed. This pushes the rocket forwards: thrust from pushing material the other way.
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What does a satellite do?
A satellite orbits a larger body in space. Artificial satellites carry equipment for tasks such as observing weather, relaying messages or research.
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Why do satellites stay in orbit?
Earth's gravity pulls a satellite inward while it moves quickly sideways. With the right combination, it keeps falling around Earth instead of hitting the ground.
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How do people sleep on a space station?
People and loose objects float inside the space station. Astronauts secure themselves in sleeping bags so they do not drift away.
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How do people eat and drink in space?
In the space station, drops and crumbs can float away. Drink pouches and suitable packaging help keep food contained.
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How does a space capsule return to Earth?
A returning capsule changes its path to enter Earth's air. There it slows sharply and gets very hot.
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How does a robot explore Mars?
A Mars rover is a mobile research robot. Cameras and instruments examine rocks and ground.
Open learning page →Discovering our Earth
What happens in a volcano?
Molten rock can rise through openings from inside Earth. Below the surface it is magma; above it, lava.
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How do mountains form?
Many mountain ranges form when Earth's plates move together. Rock folds, breaks and rises.
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Why is the sky blue?
Sunlight contains many colours. Air particles scatter shorter-wavelength light especially strongly in different directions.
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Why is seawater salty?
Water dissolves material from rocks, and rivers carry dissolved salts to the sea. When seawater evaporates, most salt stays behind.
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Why do tides rise and fall?
The Moon's pull differs across Earth, and the Sun contributes too. This creates tides.
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How do fossils form?
Remains or traces can survive if quickly covered under suitable conditions. Over long times they become fossils.
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Why do earthquakes happen?
Parts of Earth's solid surface move very slowly. Rock can get stuck and then suddenly slip.
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Why are the poles so cold?
Near the poles, sunlight strikes the ground at a shallow angle. Its energy spreads over a larger area, warming it less strongly.
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How does running water shape a valley?
Flowing water can wear away and carry off soil and rock. Over a long time a river can cut into the landscape and shape a valley.
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Why do rocks contain different minerals?
Many rocks contain different minerals: natural substances with an orderly internal structure. They combine in different ways as rocks form.
Open learning page →Discover Natural Wonders
Camouflage, trapping leaves, Ice Age animals, storms, caves and the deep ocean: nine learning journeys with pictures, examples and explained terms.
Explore topics →Space & the Future
From Earth to other planets: discover spaceflight, models and questions researchers investigate.
Explore topics →History & Ancient Cultures
How did people live in the past? Examine buildings, objects and writing, distinguishing evidence from invented stories.
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