You’ve heard of “Why is the sky blue?”, but have you heard of “Why don’t clouds fall?” In a sequel of common questions asked about weather phenomena, this post will explore the science behind the fluffy white puffs we see in the sky.
Clouds & Floating
The thought process goes like this: If water is heavier than air, and if clouds are made of water droplets, then why don’t they fall?
First of all, we need to understand that the water droplets in clouds are not the same size as the ones that fall down. Raindrops are waaaay bigger than cloud droplets. In fact, in terms of average diameters, raindrops are 100 times bigger. In terms of volume, a raindrop is 1 million times bigger.
Because cloud droplets are so so tiny and light, they have a really hard time falling to the ground. Theoretically, they would fall ever so slowly to the ground, kind of like tiny parachutes. This is because the friction between the droplet and the surrounding air slows it down to an imperceptible amount. It’s similar to how dust particles appear to float in the air when you see them through a ray of light. However, gravity and friction aren’t the only forces acting on the droplets. When air close to the ground heats up from the sun, it expands, becomes less dense, and rises up. The wind created from this movement is called an updraft. Updrafts keep the tiny water droplets in the sky by constantly pushing them upward.
Clouds & Colours
If clouds are made of water particles and water itself is transparent, why are clouds white (and not transparent)?
The answer is quite simple: when sunlight hits these cloud droplets, they scatter the light. Because sunlight is white, clouds take on that colour as well.
And the reason why storm clouds are grey? Since the droplets are bigger before a rainstorm, less light can pass through the cloud, making it appear dark.
During sunsets and sunrises, we see clouds turn shades of red, orange, yellow, pink, and purple. When the sun is close to the horizon, sunlight has to go through more of the atmosphere and gets scattered by more particles. Because blue wavelengths of light are scattered to a point where they’re barely noticeable, the wavelengths that remain tend to be reddish in colour. The reddish light hits the clouds and voilà! You have sunset-coloured clouds.
Clouds & Us
I think everyone has looked up at the clouds and compared their shapes to other things at least once in their lives. I also think everyone has encountered the question “Why is the sky blue?” at least once in their lives. Finally, I think everyone has admired a beautiful, out-of-the-world sunset at least once in their lives. The point I’m getting at is this: Weather phenomena play a big part of our lives on Earth. And it’s really surprising how much people don’t know about something so universal – even I didn’t know why clouds float before writing this post! But now I do, and you do too.
The next time you’re gazing at some clouds on a bright sunny afternoon, I hope that knowing why they float brings a bit more satisfaction and enjoyment to your day.