As soon as I read the article, Scientists discover an ocean 400 miles beneath our feet that could fill our oceans three times over, I thought about the ancient Sumerian stories of Marduk aka Nibiru and Tiamat, as well as the so-called “Hollow Earth” theory.
Allegedly, in ancient Sumerian tablets, there is a story that associates Marduk and Tiamat with planetary bodies. The characters are later described in Babylonian texts as gods as well. Marduk aka Nibiru aka Planet-X is told to have been in a counter-directional orbit of the other planetary bodies of the time, which included all the current planets, minus Earth and our moon. The planet between Mars and Jupiter was Tiamat, a planet made from only water–salt water and fresh water.
The narrative goes on to say that Marduk was pulled into the orbit of Tiamat, and the satellites (moons) of Marduk smashed Tiamat, splitting Tiamat into pieces (or in Babylonian myth-they fought a battle as gods). The result of this cosmic collision created the Earth and what is now the asteroid belt. Subsequently, the moon was pulled away from another celestial body into the orbit of Earth. The cosmic disturbance also changed the orbit of other planets in the system, pushing Pluto out past Neptune.
The “Hollow Earth” Theory basically theorizes that the Earth is concave (like a bowl or an egg), that the inside is a vast open space where there is an inner-sun, oceans, and springs of fresh water. There’s some people living in there too, according to the theory.
So, in conclusion, humans don’t know everything yet.