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Why leaves change colour in autumn
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Why the northern lights appear where they do
27 September 2026
Charged particles, not sunlight, make the aurora. Here is how Earth's magnetic field shapes the glow, its colours and how far from the poles it reaches.
What causes the tides, and why they vary by coast
24 September 2026
The Moon and the Sun pull on the whole ocean, creating two bulges of water. Here is how that becomes two tides a day, and why no two coasts look the same.
Why the sky is blue and sunsets are red
24 September 2026
One process, Rayleigh scattering, explains both a blue midday sky and a red sunset. The difference is how much atmosphere the sunlight crosses.
What a light-year really measures
24 September 2026
A light-year is a distance, not a span of time. It is how far light travels in a year, and it doubles as a measure of how far into the past we look.
How GPS actually fixes your position
24 September 2026
Your phone never knows where it is. It measures how long radio signals take to arrive from four satellites and solves the geometry from there.
How earthquakes are measured: magnitude and intensity
24 September 2026
Magnitude describes the size of an earthquake at its source, while intensity describes the shaking at a particular place. The two are often confused.