How Do Computers Recognise Images?
An image is a grid of numbers. Recognition works by passing that grid through layers that detect progressively more complicated patterns, from edges up to objects.
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Why Did the Bronze Age Collapse?
In a few decades around 1200 BC, the interconnected palaces of the eastern Mediterranean were destroyed and several states disappeared. Nobody agrees on a single cause, and that may be the answer.
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Why Ancient Egypt Lasted So Long
Three thousand years of continuous civilisation is an outlier. Egypt had a river that made farming predictable, deserts that made invasion difficult, and an administration built to exploit both.
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How Do We Know Atoms Exist?
Nobody sees atoms with ordinary light. They were inferred from Brownian motion, measured indirectly for a century, and then eventually photographed one at a time.
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How the Calendar Was Invented
A calendar has to reconcile three cycles that do not fit: the day, the month and the year. Every calendar in history is a different answer to that arithmetic problem.
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How a Computer Stores Information
Everything a computer holds is patterns of two states. The interesting part is not the binary, it is the ladder of storage types trading speed against size and cost.
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Using Supernovae to Hunt for Particles Nobody Has Seen
A physics team has proposed using the gas a dying star throws off before it explodes as a detector for extremely weakly interacting particles, and set new limits using a recent supernova.
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How Do We Know the Age of the Earth?
The Earth is about 4.54 billion years old, and we know that because certain atoms decay at a fixed rate. Rocks containing them behave as clocks that started when the rock formed.
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How Does a Plane Stay Up?
A wing generates lift by pushing air downwards. The popular explanation involving air travelling further over the top is wrong, and the correct one is simpler than it sounds.
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How Encryption Protects Your Data
Encryption turns data into something unreadable without a key. Modern systems use two different kinds at once, because each solves a problem the other cannot.