The blue planet

The chapter opens with the writer Jules Verne, in 1870: 'The ocean is everything. It covers seven-tenths of the terrestrial globe... The globe began with the ocean, so to speak, and who knows if it will not end with it.'

Turn a globe gently, or look at a photo of the Earth taken from the Moon. What colour do you see most? Blue, of course. And blue stands for water.

Almost three-fourths of the Earth's surface is covered with water (about 71 parts out of every 100). That is why, seen from space, the Earth looks mostly blue, and why early astronauts lovingly called it 'the blue planet'. The largest bodies of water on the globe are called oceans.

The photo shows at least one other colour: brown. That is land, which covers a little over one-fourth of the globe (about 29 parts out of 100).

Two words to keep apart:

• A large body of land is a landmass.
• A large continuous stretch of land is a continent. 'Continuous' means unbroken: the land runs on without the sea cutting it.

Oceans and continents both shape the Earth's climate. They affect plants, animals and so human life too, and we can see their effect all through our history, our culture and our daily lives.

A piece of that culture is still in use. The emblem of the Indian Navy carries the motto 'Śham no Varuṇah', which means 'Be auspicious to us, O Varuṇa.' It is a prayer to Varuṇa, a Vedic deity linked with the oceans, the sky and water in general.