Part 6/10:
The idea of extra spatial dimensions dates back to Kaluza-Klein theory in the 1920s, initial efforts to unify gravity with electromagnetism. While significant strides in experimental physics have been made, conclusive evidence for the existence of these dimensions remains elusive. Recent gravitational wave detections from LIGO have largely ruled out the existence of large extra dimensions but left the door open for compactified extra dimensions—those that are tiny and hidden from our perception.