· Why does rain not fall in the form of a mass like a waterfall but fall as single drops?
· What is the shape and size of raindrops?
· Why does rain not heat up due to friction force and fall in the form of boiling water?
Every year, approximately 45 million cubic meters of water vaporize from the oceans. The vaporized water is turned into clouds and moved to the land via winds. So every year between three and four cubic meters of water moves from the oceans to the lands, meaning where we live. Water, which people cannot control the circulation of and cannot live without it, is sent specially. Also there are many wonders about the formation of water and its fall onto the ground. In the Qur’an, Allah reveals the erudite characteristics of the rain, which is one of the clearest signs that a person should be “thankful”, as such:
"Have you thought about the water that you drink? Is it you who sent it down from the clouds or are We the Sender? If We wished We could have made it bitter,so will you not give thanks?" (Surat al-Waqi‘a, 68-70)
It is Allah’s Mercy That Rain Falls Drop by Drop From the Clouds
One of the wonders Allah created in rain is that rain does not fall onto the ground in the form of a large water mass like waterfalls. If rain fell on the ground in this form, it would not be possible for people to continue their daily lives during rainy seasons and floods would form during every rainfall. These floods would drag away everything in front of them and cause serious damage, both material and spiritual. However, due to the laws of physics created by our Almighty Lord, it falls on the ground in drops and by decreasing its speed turns into the precious water that is the source of life for all beings.
The reason that rain falls in drops is that water droplets are formed inside clouds. As is known, a cloud is formed by water vapor being thickened with dust and electrically positive charged particles. The diameter of these particles are generally between one and ten microns. (1 micron = 0.001 millimeters.) When clouds move upwards at a certain speed (1-10 meters/sec), they take water droplets with them naturally. As the water droplets rise up, they get bigger as their volume increases. Two or more droplets unite and form a rain drop. The air can no longer carry these drops and the rain drops begin to fall to the ground.
Since big drops fall faster than small drops until they reach a fixed speed, big drops and small drops crash and unite. Drops, which get bigger through crashing and uniting, encounter air resistance which distorts the shape of the water drop, spreads and turns into many small droplets in a short time, something on the order of six hundreths of a second. Since the speeds of drops of the same size are the same, and they move in the same direction, they do not crash with one another.
Raindrops Slow Down When Falling On the Ground by Our Lord’s Inspiration
One of the wonders our Almighty Lord created in raindrops is certainly the falling speed of rain. When an object of the same size and weight as a raindrop is left from a height of 1,200 meters, it would get faster gradually and fall on the ground with a speed of almost 558 kilometers per hour. If the raindrop would fall from this height in the same way, this time all crops would be destroyed, places of settlement, houses and cars would be damaged and people would not be able to walk without taking necessary precautions. However, such an incident never occurs; no matter how high a distance raindrops fall from, when they reach the ground their speeds are only eight to ten kilometers per hour. The reason for this is that the raindrop has a shape that increases the frictional force of the atmosphere and makes it fall slower. If the raindrop had another shape, or if the atmosphere had no friction force, it would be enough to take a look at these numbers to see the disasters the world would face every time it rained.
- The minimum height of rain clouds is 1,200 meters. The effect of a single drop that falls from this height is equal to the fall of a one kilogram weight from a height of 15 centimeters.
- There are also rain clouds up to 10,000 meters high. This time a single drop would have the same effect of a one kilogram weight falling from 110 centimeters high and thus people would need to take shelter by taking major precautions.
As it is seen, Allah defines the falling speed of rain and makes rain beneficial for all beings:
"And We sent down blessed water from the sky and made gardens grow by it and grain for harvesting" (Surah Qaf, 9)
Rain Not Being Hot is Allah’s Mercy Over His Servants
If rain drops got heated owing to the effect of friction force and fell on earth in the form of boiling water, life would never happen. However, rainwater is cold to maintain life due to our Lord’s knowledge and mercy for His servants.
As it was told previously, after rainwater is separated from the cloud it speeds as it falls down. As raindrops fall down with the effect of gravity due to their weight, the air’s resistance tries to hold it up at the same time. The droplet speeds up until the air resistance is equal to the force of gravity that affects the drop. The speed when they are equal is the terminal speed, and the droplet continues its journey down at this fixed speed. When the droplet goes down, it becomes heated due to friction. However, this temperature is used for the vaporization of the droplet. Vaporization causes cooling on the surface of the droplet. Thus, a droplet gets smaller as it falls down, but it does not get hot. Therefore, the droplet is not hot and it does not rain scalding hot water from the skies.
Almighty Allah reveals that He controls the rain and turns it into a life source for people and all living things in one verse:
"It is He who sends down water from the sky. From it you drink and from it come the shrubs among which you graze your herds." (Surat an-Nahl, 10)
Fertilizing Feature of the Rain
Rain is an important fertilizer. Even poor soil can gather all the elements plants need within a century, even through fertilizers that come via the rain. Forests also grow and feed with the help of these sea-origin aerosols. In this way, 150 million tons of fertilizers fall on earth’s surface every year. Without this natural process of fertilization, there would be very little flora on earth and the balance of life would be distorted.
It is a great blessing of our Almighty Lord that He sends a certain amount of water down from the sky, that this water has is drinkable and can revive a dead region. In one verse, our Lord’s knowledge of creation is revealed as such
“Do you not see that Allah sends down water from the sky and threads it through the earth to emerge as springs and then by it brings forth crops of varying colors, which then wither and you see them turning yellow and then He makes them into broken stubble? There is a reminder in that for people of intelligence.” (Surat az-Zumar, 21)
The source of rainwater is vaporization and 97% of vaporization occurs in “salty” waters. However, rainwater is sweet. The reason that rainwater is sweet is another law that Allah sets. According to this law, water does not carry any other foreign substance no matter if it is vaporized from saline seas, mineral lakes or mud flats. As it is revealed in the verse, "We send down from heaven pure water..." (Surat al-Furqan, 48), it falls on the ground in a clear and clean form.
Clouds That Form the Rains Are the Examples of Allah’s Art of Variety:
In the Qur’an, verses about the clouds, which have great importance in the formation of rain, give information about the variety in Allah’s creation as well:
"It is Allah Who sends the winds which stir up clouds which He spreads about the sky however He wills. He forms them into dark clumps and you see the rain come pouring out from the middle of them. When He makes it fall on those of His slaves He wills, they rejoice,"(Surat ar-Rum, 48)
- The size of a mid-sized cloud with a diameter of half a kilometer is four billion cubic meters and there is 1.5 million kilograms of water inside
- No cloud is the same with another in terms of shape and size. This is because there are so many factors such as air flows that affect their formations, temperature, pressure, the amount of dust in the air and so forth, so it is not possible to obtain the same conditions in two locations in the atmosphere, which is very changeable.
- Water, which vaporizes from the heating ground, rises up to the sky in the form of light, minute water vapor. As pressure decreases and air gets cold at a certain height, they become small water dropletss and form the clouds. At the start, the diameter of these drops is a few microns. (a typical human hair is 100 microns.) For the formation of an average raindrop, millions of these have to unite.
- Even though clouds are very heavy, the reason that they can stay hung in the sky is that these drops are very small. If there is at least 1,000 tons of water inside a cloud, the size of this air is one thousand times heavier than this. Therefore, clouds travel in the sky, until the raindrops inside them grow and fall onto the ground by getting heavy. Actually, since the formation of raindrops continues while it is raining, they do not get lost suddenly by emptying the water inside the cloud.
- The raindrops that are formed first are very small. Thus they reflect the sunlight directly and such clouds appear as white. As these drops unite and get bigger, meaning thicker, they reflect the light less. Therefore, rain clouds are dark, gray and sometimes even close to black in color.
