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Gallery 3

Geochron

A back lit display of a world map with only the centre part lit, while the rest is in dark.

A model of how sunlight moves across Earth's surface to create day and night in different parts of the world.

How it works

An illuminated map of the world shows where sunlight is shining on Earth at the moment and can be used to calculate the current time anywhere in the world

Things to try or ask around the exhibit

  • How can we use this map to work out the time in London right now?
  • What do the dark and light areas represent?
  • Why is the pattern of light shaped this way?

Background

‘Geochron’ comes from the words geo (Earth) and chrono (time). The Earth spins on its axis once every 24 hours and the Geochron map also cycles once every 24 hours to show how sunlight illuminates the world as Earth spins.

The area of Earth that is currently experiencing sunlight is illuminated on the Geochron. The left edge of the illumination shows where sunrise is occurring on Earth right now. The right edge of the illumination shows where sunset is occurring on Earth right now.The peak at the top of the illumination shows where the Sun is directly overhead at the moment.

Finding the science in your world

This Geochron shows where sunlight is shining on Earth at the moment. The Geochron can also be used to calculate the current time anywhere in the world.

Throughout the year, the shape of sunlight on Earth changes because the Earth is tilted on its axis. At equinox (in March and September) the Sun is overhead at the equator, everywhere on Earth has equal amounts of sunlight and the edges of the illuminated area are straight.