Planets are roughly spherical because they form in a rotating dust cloud around a rotating, newly-forming star. Gravity pulls the material together as it collapses into a “ball”. The equator is an imaginary line around a planet, exactly half-way between the two poles. The rotation also causes a “bulge” to form at the equator so that the Earth is more of a slightly “squashed ball".
It is hard to say who first found the equator. Ancient Greeks and Polynesians who travelled by sea, navigating by the stars, would have been aware that the Earth was spherical. Christopher Columbus is often believed to have proven that the Earth was spherical rather than flat, but this appears to be a myth; the Earth was known to be spherical before his time.
- Catherine Bell.
It is hard to say who first found the equator. Ancient Greeks and Polynesians who travelled by sea, navigating by the stars, would have been aware that the Earth was spherical. Christopher Columbus is often believed to have proven that the Earth was spherical rather than flat, but this appears to be a myth; the Earth was known to be spherical before his time.
- Catherine Bell.