Have you ever wondered how big, puffy clouds float in the sky on a summer’s day? How do they stay afloat? Why don’t they fall from the sky? Well, it’s because of a combination of interconnected reasons.
Clouds are produced through the process of condensation. Water vapor condenses into water droplets. Then, along with warm air, water vapor rises above the cold air that surrounds it. Steam from a boiling water kettle or your breath on a freezing winter day are examples of rising water vapor.
Cloud starts forming when the sun heats and evaporates water on the planet’s surface. The process then produces warm and moist air, which is lighter than the cold air above it, seemingly like how hot air balloons soar into the sky. Since it is less dense, warm air rises and cools off as it passes through the cold air. Since cold air is unable to retain as much moisture as warm air, the vapor condenses into a liquid, and then, clouds are formed.
Upon formation, clouds can hold different amounts of water, resulting in varying sizes and shapes and ranging from feather-like cirrus to huge cumulonimbus thunderclouds.
So, the sun heats and evaporates water on Earth’s surface, warm water vapor rises, cools off, and condenses. Viola! Clouds are formed in different sizes and shapes. But how do they stay afloat?
First, the water droplets in a cloud are extremely small. On average, they are only about one micron, or one-hundred-thousandth of an inch wide. It is typically half the width of a human hair strand and about the size of dust particles.
But, while dust is still more massive and affected by gravity, it can still float for some time before falling on the ground. Even the mildest air currents are sufficient enough to keep them swaying in the air, which is why you see dust motes dance in a ray of sunlight.
Water droplets act in the same manner as dust particles would. The difference, however, is there is a ‘vessel’ that keeps clouds afloat. There is a sustained flow of warm moist air that gets in contact with the cloud. What it does is pushes the cloud upward, keeping it afloat.
Another reason is that clouds tend to be warmer than the air surrounding them as they are better in absorbing the sun’s energy compared to the air that surrounds them.
Lastly, unlike other things, the weight of the clouds is scattered throughout itself, which makes the effect of gravity on them negligible.
Clouds don’t stay floating. If in case the surrounding air becomes warmer than the cloud, the air will be able to contain the moisture as water vapor. Thus, the clouds disappear.
There are also times when clouds grow so large, and the moisture within the cloud begins to stick together. The water droplets become too heavy, overwhelm the force of the upward air, and start to fall, and are now called “rain.”
- Cloud (Wikipedia)