We began by talking about whether an Oxygen atom in Kohlapur is identical to an Oxygen atom in Kohima. In fact, all Oxygen atoms anywhere in the Universe are exactly identical!

This is an amazing fact: Even though in ordinary life, we don't experience even two objects that are exactly identical, billions of atoms are identical to each other.

This is how scientists can talk about properties of stars that are billions of kilometres away. Because atoms are identical everywhere in the Universe, learning atoms' behaviour here on Earth helps us understand properties of faraway objects.