BILLE
Imagine you throw a toy into the air. It flips, spins, and twirls before falling down. But no matter how it falls, it always lands on the same side. Sounds like magic, right? Well, scientists have actually made such a shape! They call it Bille.
What is Bille?
Bille is not just an ordinary toy. It’s a special pyramid-shaped object called a monostable tetrahedron.
Tetrahedron means it has 4 triangular faces.
Monostable means it has only one stable resting position.
No matter which side you place it on — A, B, or C — Bille will slowly tip over and settle on side D every time.
The puzzle behind Bille: Back in 1966, two famous mathematicians, John Horton Conway and Richard Guy, asked a big question:
"Can anyone make a tetrahedron that always lands on the same side?"
For many years, no one could solve the puzzle.
Then, Professor Gábor Domokos and his student Gerg Almádi from the Budapest University of Technology in Hungary took up the challenge. For three years, they tested computer models and different shapes until they found the secret:
The tetrahedron had to be mostly hollow.
One side needed to be thousands of times heavier than the others.
How they built it: With the help of engineers, they made Bille:
The frame is light carbon fibre tubes.
One side is made of very heavy tungsten-carbide alloy.
It’s about 50 cm long (like a guitar) but weighs only 120 grams.
The name “Bille” comes from the Hungarian word billen, which means “to tip”.
Why is Bille Useful?
Bille is more than just a science trick. It can help in important ways:
1. Space Missions – Lunar landers that fall on uneven ground sometimes can’t get back up, ending the mission. A Bille-shaped lander would always land in the right position, saving millions of dollars.
2. Robotics – Robots made with Bille’s design could stand up by themselves after falling, making them better at moving on rough ground.
Fun Fact – What is a Tetrahedron?
A tetrahedron is a 3D shape with:
4 triangular faces
4 corners (vertices)
6 edges
It looks like a pyramid with a triangle at the base, and all its faces are flat.
