Recombination (cosmology)

Recombination is something that happened a really long time ago, about 13.8 billion years ago, when the universe was much younger. At that time, the universe was filled with hot, glowing gas made up of lots of small particles called protons, neutrons and electrons. The protons and neutrons were stuck together to make something called hydrogen, and the electrons were zooming around them like buzzy little bees.

But then something really amazing happened. The gas started to cool and the protons and electrons got closer together. When the electrons got close enough, something magical happened - they joined up with the protons and made a new type of gas called hydrogen gas. This new gas was made of little hydrogen atoms - each atom had one electron and one proton stuck together.

The result of this joining up of protons and electrons is called recombination. It was so important because it created the first stable atoms in the universe and laid the foundations for stars and galaxies to begin to form.