The Search for the Bottom Throughout history, humans have searched for the ground floor of reality, the most fundamental level from which everything else emerges. The ancient Greeks proposed atoms: indivisible particles that couldn't be broken down further. Two thousand years later, we discovered atoms could be split, revealing electrons, protons, and neutrons. Surely these were fundamental? Then we found that protons and neutrons contained quarks. Perhaps quarks are fundamental? String theory suggests they might be vibrations of one-dimensional strings. Perhaps strings are fundamental? Some theories propose even strings are composed of more basic structures; branes, loops, or mathematical objects we don't yet have names for. Each generation believes it has reached the bottom, only to discover deeper structure. This could be a temporary state, we just haven't dug deep enough yet. Eventually we'll hit the truly fundamental level, and the digging will stop. Or it could be...