The question “What is a cloud?” people wondered back in those distant times, when only birds and the clouds themselves flew across the sky. Wikipedia did not yet exist, and no one had yet invented or published the “Children’s Encyclopedia”. Therefore, some dreamers have come up with everything to explain this natural phenomenon.
Because clouds appear so soft and fluffy from below, there was a time when people thought they were made of fluff.
There have also been more amusing assumptions about what these celestial formations are made of. They even said that the building material of the white giants floating in the sky is cotton candy.
Of course, this is fiction. Scientists learned what the cloud is made of at the end of the 18th century. This happened when humanity found a way to rise into the sky. It was then that we were able to answer the question: what does a cloud consist of? It turned out that the clouds that appear white and dense from below are actually ordinary fog. So walking in foggy weather is like traveling through a cloud.
In those same years, people learned what clouds are made of. After all, before this, their nature was also explained in different ways. But all this will be discussed a little later.
In general, clouds can consist not only of water droplets, like ordinary fog, but also of ice crystals. It all depends on the height at which they form.
Most often, clouds appear at an altitude of 6 to 20 km from the surface of our planet. This part of the atmosphere is called the troposphere. This is where clouds consisting of water droplets form. The temperature inside such formations is usually above -10 0 C. Clouds that form at this altitude can have different structures and shapes.
There are also clouds that appear much higher. For example, the so-called nacreous clouds are born 20-25 km from the Earth. However, the record holders are noctilucent clouds, which are practically invisible without special equipment. Their cradle is located at an altitude of 70 to 80 km above sea level.
Why and how do clouds appear?
But how do clouds form? This is a very important issue for children. To answer this, you need to get acquainted with another interesting physical phenomenon - condensation. What is it?
We have all seen steam coming out of the spout of a boiling kettle more than once. If you place a cold saucer under this stream, droplets of water will appear on its surface. This phenomenon is called condensation.
Approximately the same processes occur in the upper layers of the atmosphere. Water vapor, rising higher and higher, cools and begins to condense into liquid droplets, from which clouds form. The size of these droplets is incredibly small - 100, and sometimes 1000 times less than 1 mm. If the steam manages to rise very high, then it will turn not into a liquid, but into a solid state. Therefore, in the uppermost layers of the atmosphere, clouds consist of tiny pieces of ice.
But for steam to begin to condense, just lowering the temperature is not enough. The center of each droplet or crystal is the smallest speck of dust, around which moisture has collected.
By the way, it is for this reason that very large clouds can often be observed over cities where there are a lot of cars or large factories. Indeed, in such places there are much more different air polluting particles in the atmosphere than in sparsely populated areas of our planet.
Why do clouds fly?
From the surface of the Earth, the clouds seem so light and airy. In fact, they can weigh many tons. How can a whole cloud of water, consisting of a huge accumulation of water droplets, stay in the air? Everything is very simple. The size of each droplet is so small that even a small flow of air rising from the Earth stops their fall.
Scientists have calculated that the updraft speed to hold the cloud can be as low as 50 cm per second. If we translate this number into a more understandable form, we get a very small value - 1.8 km/h. And this is much less than walking speed.
What types of clouds are there?
Beautiful white mountains floating across the bright blue sky are always a delight to the eye. But why do they appear this way?
It turns out that the more sunlight passes through the clouds, the whiter they appear to us from Earth. A gray cloudy sky only means that the cloud layer is very dense and the sun’s rays practically do not pass through it. But black clouds most often simply contain a lot of dust. Cloud formations of this color often appear over industrial areas, where air pollution is the worst.
But clouds differ not only in color, but also in shape. The common name for clouds usually describes their appearance. Although scientists have come up with a very complex classification of cloudiness, only three types of clouds can be clearly distinguished.
It is this type of accumulation of water vapor in the sky that we most often call clouds. These are the same dazzling white giants, smoothly changing their shape. They are the ones people love to watch, imagining who they are like. Such cloudiness is not at all annoying. And this is not surprising, because cumulus clouds are the companions of good weather.
However, it is this type of cloud that periodically turns into clouds, which scientists call cumulonimbus clouds. What is a cloud made of? Actually from the same thing as all clouds. As a rule, its lower layers are water droplets. But the upper part of rain clouds consists of ice crystals. Because of this multi-layered nature, the height of the clouds can be very large, sometimes reaching 10 km.
Stratus clouds are no longer so beautiful. Most often they are gray in various shades. Such clouds are quite dense and consist exclusively of droplets ready to fall to Earth. They don't swim that high above the surface. In this case, the height of the clouds above the ground is approximately 1-2 km.
If the sky is covered with stratus clouds mixed with cumulus, then it’s okay - the weather is unlikely to worsen. This type of cloudiness is often called stratocumulus clouds. By the way, it is precisely this type of cloud that appears before the mind’s eye when you need to answer the question: “What is cloudiness?” But a solid gray blanket always suggests a long and tedious rain.
And this type of cloud is located quite high. They can be observed at approximately seven kilometers altitude. They look like little lambs or smears of oil paint smeared in the sky.
Such cloudiness indicates an imminent change in the weather, not for the better. By the way, cirrus clouds are the most photogenic. The photos in which they are present look incredibly impressive.
The clouds are very heavy. On average, their weight is about 10 tons. In addition, they are also huge in size. A single cloud can extend over 10 km, and thunderclouds can extend a similar distance in height.
The lifespan of clouds depends on air humidity. At normal humidity, the cloud can exist for a very long time. But at low temperatures, the droplets of water that make up the cloud will begin to evaporate quickly and it can survive for no more than 15 minutes.
It’s hard to imagine, looking at the clouds floating across the sky, that this miracle of nature can be created at home. Although in fact a real cloud can be made artificially. True, this will require special equipment. Dutch artist Berndnaut Smilde figured out how to make clouds. His homemade clouds don't last long, about 10 seconds. But during this time they can be photographed or the moment of the birth of a small cloud can be filmed.
Such a phenomenon as cloudiness is observed not only on Earth, but also on several other planets of the solar system. Clouds have been discovered in the atmosphere of Venus and Mars, as well as on Saturn's moons Titan and Neptune's Triton.
In 2004, several meteorologists and physicists united as part of the international organization Cloud Lovers Society. They not only themselves admire these bizarre creatures of the earth’s atmosphere, but also encourage everyone to raise their eyes to the sky to admire the beautiful and varied clouds.
Surprisingly, even scientists don’t know everything about clouds. Their study continues to this day. Both Russia and the USA are still working on programs to determine all the properties of these beautiful, snow-white, airy islands.
