What is the external structure of Earth?
It has been known for more than 2000 years that the Earth is round, but we were able to actually see this much later only when we flew into space. The knowledge why we do not fall off from Earth is much more recent. A journey as describes by author Jules Verne in his book Journey to the center of the earth was, after all, impossible. Only one thing was known: The earth is made up of soil, rocks and water. Today, we know that the Earth is also surrounded by an air cover called the atmosphere.
What is the internal structure of earth?
Like an onion, the Earth has several layers. The outermost layer, the Earth’s crust, has an average depth of about 40km. As compared to the diameter of Earth, which is around 12,700 km, the crust is very small. It is primarily made up of solid rocks. Below the crust is the solid mantle, reaching to a depth of about 2900 km. due to the heat inside the Earth, the mental consists of solid and molten rocks. Below the mental is the core, made up of iron and nickel. The deeper one travels inside the Earth, the hotter it is. The temperature in the core is 4000 to 5000 degree C.
How do we discover what is inside the Earth?
Caves and mines go only up to one to two km inside the Earth. Even the deepest wells of the world, such as the one 12 km deep in Russian Kola Peninsula or the 9-km-deep one in Upper Palatinate, hardly scratch the Earth’s crust! One can ‘look’ deep inside the Earth in aftermath of earthquakes or by creating nuclear explosions. The explosions generate sound or seismic waves. They also throw off rock particles. By measuring their intensity and timings, scientists discover the composition of the Earth’s interiors.
How did we discover that the Earth is round?
Around 3000 years ago, people believed that Earth was flat. But people wondered why ships disappeared at the horizon. Sailors too returned from journeys and were proof that the ships did not fall off from the edge of the Earth. The simplest explanation was: the earth must be round. The final proof came in the year 1522 after the expedition of Ferdinand Magellan, who was the first to sail around the Earth.
Why do we not fall off the earth?
Gravity is the force of Earth that attracts every object towards itself. From our perspective this force always acts downwards. For a long time people did not believe that the Earth is round because the people ‘underneath’ the sphere would have actually fallen down. In 1687, Ser Isaac Newton proved that the force of gravity always acts towards the center of the Earth. On the Earth, force of gravitation always acts ‘downwards’ irrespective of Eskimos in the Arctic region, people in Europe or inhabitants of Australia.
What is the atmosphere made up of?
The word ‘Atmosphere’ means a gaseous cover enveloping a planet. Without atmosphere life would not have been possible on Earth: one-fifth of the atmosphere is oxygen and four-fifth is nitrogen. Like the Earth’s interior, the atmosphere too is made up of many layers. All animals and plants live in the lowermost layer of the atmosphere called the ‘troposphere’. All weather phenomena take place in the troposphere. Even aeroplanes fly in the outer edge of the troposphere. The stratosphere, the mesosphere, the ionosphere and the exosphere lie above the troposphere.