Interesting facts about Earth, our blue planet

In the whole known universe, Earth is the only place where life has been found. Seen from space, it looks like a shining blue ball, because most of it is covered by water. Here are interesting facts about Earth — from its age, size and inner layers to the things that make it fit for life.

Earth at a glance

Earth is not perfectly round

Earth spins on its axis, and this spinning has made the region near the equator bulge outwards slightly, while the poles are a little flattened. So Earth's radius at the equator is about 21 kilometres more than at the poles. This shape is called a "geoid". About 1,500 years ago the Indian mathematician and astronomer Aryabhata wrote that Earth turns on its axis, and that this is why the stars appear to move.

Earth's layers

• Crust: the thin outermost layer — about 5–10 kilometres thick under the oceans and up to 70 kilometres under the continents. We live on it.
• Mantle: a layer of hot, slowly flowing rock about 2,900 kilometres thick.
• Outer core: molten iron and nickel. Its movement creates Earth's magnetic field.
• Inner core: a solid ball of iron and nickel, with a temperature of more than about 5,000 °C — roughly as hot as the surface of the Sun.

Did you know? Even sitting still, you are travelling very fast! At the equator Earth spins on its axis at about 1,670 kilometres an hour, and it moves round the Sun at about 30 kilometres a second — more than a hundred thousand kilometres an hour.

Why do the seasons change?

Many people think summer happens because Earth comes closer to the Sun, but the real reason is the 23.5-degree tilt of its axis. When the northern part of Earth leans towards the Sun, the Sun's rays fall more directly there and the days are longer — that is summer in the northern hemisphere. At the same time it is winter in the southern hemisphere. A "leap year" comes every four years because Earth's year is about six hours longer than 365 days.

Water, air and a magnetic shield

• Water: about 97% of all the water on Earth is salty. Most of the fresh water, too, is locked up in ice and glaciers — read Major rivers of India.
• Air: the atmosphere is about 78% nitrogen, 21% oxygen and about 0.9% argon, with a very small amount of carbon dioxide.
• Magnetic field: it works as a shield against harmful particles coming from the Sun. The coloured lights called "auroras", seen near the poles, are a result of it.

The highest and the deepest

Earth's highest point is Mount Everest (8,848.86 metres) and its deepest is the "Challenger Deep" in the Mariana Trench of the Pacific Ocean (about 11 kilometres). So if Everest were lifted and placed in this trench, even its summit would stay more than two kilometres under water. Read about India's peaks in The major mountain peaks of India. Earth's place in the solar system: The planets of the solar system.

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