25/01/2026
So interesting. Lesotho is just a short drive away.
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Basotho Women's Winnowing (Ho Olosa) Is A Science Experiment!
Imagine standing in a golden field in Lesotho as the sun begins to set. You might see a group of women standing tall, holding beautiful woven baskets called liroto (singular: seroto) high above their heads. They are performing a traditional task called Ho Olosa, or winnowing.
While it looks like a graceful dance, it is actually a clever science experiment! Let’s look at how it works.
The Magic of Gravity and Wind
After the sorghum grain is harvested, it is mixed with "chaff", the dry, leafy bits that we can’t eat. To separate them, the women use a "power" we see every day: gravity.
When the grain is poured from the basket, gravity pulls everything down toward the earth. But there is a catch! The sorghum grains are heavy and round, so they fall straight down into a neat pile. The chaff is very light and flat. As it falls, the air pushes against it (this is called air resistance), and the wind carries it away like a tiny kite.
In Engineering, this is called Fluid Dynamics and Particle Seperation.
Creating Their Own Weather
What happens if the air is perfectly still? The Basotho women have a scientific trick for that, too! They light a small fire nearby using old scraps of plants.
As the fire burns, it heats up the air. Have you ever noticed how heat rises? This is called thermal convection. As the hot air goes up, cooler air rushes in to take its place (this cooler air is called "maelane"). This creates a tiny, "homemade" breeze that helps blow the chaff away even when there is no natural wind!
The Science is called Thermal Convection!
Smart Tools and Smart Waste
Even the basket itself is a piece of technology. The way it is woven allows the women to control exactly how much grain falls at once. Nothing goes to waste, either:
• The Good Grain: Kept for food to make porridge or bread.
• The Chaff: Used as fuel for the fire.
• The Ground: Swept clean and flat so not a single seed is lost.
