This song is about how time can slip by, but many people do not realize it until it is too late. Roger Waters got the idea when he realized he was no longer preparing for anything in life, but was right in the middle of it. He had just turned 28.
The song starts with layers of clock noises that were put together by their engineer, Alan Parsons. Each clock was recorded separately at an antiques store, and the band blended them together. Parsons wanted to use the clocks to demonstrate a new quadraphonic sound system, but they ended up using it to open the song instead. Check out the clocks in The Video..