4.5 billion years ago was an interesting time for the Earth. The atmosphere was thick and what we would now think of as toxic. The Moon, which was freshly formed, looks much more massive than it does today and faintly glows with the residual heat from its own creation. And the floor was literally lava. Everywhere. If there were any children alive at the time, they would have no chance of winning that game. But for a long time, scientists had thought this molten phase of the Earth didn’t last long. But according to a new paper, available in preprint on arXiv by researchers at the Kapteyn Astronomical Institute, it might have lasted for upwards of half a billion years.