Everyone knows the nickname of Earth “Blue Planet“. Is the earth blue… like an orange? No, of course it is a painting by the poet Paul luard. In fact, it is as blue as the oceans. A phenomenon that can be explained by various physical phenomena.
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The planet Earth appears completely blue when viewed from space. On Earth’s surface we see the continents and oceans from above. Oceans dominate and together with seas, lakes and rivers cover no less than 75% of the total surface of the Earth.
While Asia, the largest of the continents, covers an area of about 45 million square kilometers, the Pacific Ocean alone covers an area of over 150 million square kilometers. It is as much as the totality of the built countries.
Ocean blue and light
In fact, three events combine to give Earth this beautiful blue hue as seen from space:
First, as we have just noted, the earth is the same color as water. But why is the sea blue? It is essentially a matter of refraction of sunlight.
Another physical phenomenon comes into play: the dispersion of the Sun’s white light by the atmosphere.
The reflection of this diffused light from the surface of the oceans also interferes.
Why do we call the earth the blue planet?
With its seas and oceans, water covers about 75% of the surface of our planet Earth. So it’s no wonder it’s called the Blue Planet! the explanation.
A quick visit to astronaut Thomas Pesquet’s Facebook page is enough to verify that Earth is a beautiful blue color when viewed from space.
It is often overlooked by standing with its feet on the ground, but between oceans, seas, lakes, rivers and streams, the land is mostly water.
In fact, as far as we know it today, Earth is the planet with the largest amount of liquid water in our entire solar system. Nowhere else in the universe is water more abundant than gas or ice.
If our planet appears blue it is thanks to the water that covers it, but also to sunlight and our atmosphere.
A Blue planet covered with blue water
But if the earth is blue because of the water, what does the blue color of the water indicate?
When the sun’s rays hit the surface of the water, some of these rays are reflected while others go into the water. Not all wavelengths or colors that make up the Sun’s rays are absorbed by the molecules in the water at the same rate.
The blue color is absorbed less rapidly by the latter: it will eventually be absorbed at a depth of 90 meters.
That’s why the water on the surface of the earth appears blue. Actually, the water of the caves also appears blue when illuminated with white light. Water in a glass does not appear blue but transparent because it is less dark.
Since when is Earth called the Blue Planet?
At a human level, not long ago we could fly into space. So the nickname of the blue planet is not that old.
In fact, it is the astronauts who participated in the first manned space mission in the 1960s that give it the nickname. Before these trips, we weren’t sure what Earth looked like from above.
The first manned flight, Vostok 1, was launched by the Russians on April 12, 1961, from the city of Tioratum in Kazakhstan.
Onboard: the famous Yuri Gagarin, the first man to go into space. Then it was the turn of the Americans, who in 1969 sent the first astronauts to the Moon.
Currently, Russia is the country with the most flight hours in space, followed by the United States.