Your PCA is awesome. The horizontal axis seem to go from people (high level nature?) on the left to physics (low level nature?) on the right, while the vertical

Your PCA is awesome. The horizontal axis seem to go from people (high level nature?) on the left to physics (low level nature?) on the right, while the vertical axis seems to go from individuals and particles (small things?) at the bottom, up to civilizations and the universe (big things?) at the top. Maybe the Manhattan Project and Cambrian Period (not explosion) are together because they're both big things in their fields and physics and evolution are near each other horizontally?