The discussion centers around identifying the longest-running machines or mechanisms, with a focus on Big Ben and other historical devices. Big Ben, while notable, has undergone several major overhauls, leading to questions about its classification as a continuously operating machine. The age of the universe is mentioned, with references to WMAP data, but the accuracy of such dating methods is debated, highlighting a margin of error. Participants suggest that older mechanisms, such as pendulums, water wheels, and even ancient pipe organs, may qualify as contenders for the longest operational devices without servicing. The conversation also touches on the distinction between static and dynamic systems, with examples like bells, bridges, and various mechanical devices being considered. Overall, the thread explores the complexities of defining and identifying the oldest continuously operating mechanisms.