Detta diskuteras (i längd) i medföljande bok . Kort sagt var den andra monolitmen en larmanordning avsedd att visa att aporna på planeten nedan hade utvecklats till den punkt som de kunde nå sin närmaste planetariska granne och att utföra grundläggande undersökningsuppgifter. Således skulle det nu vara till nytta för monolitbyggarna att aktivera fas II av sina planer och skapa en andra sol i solsystemet för att tillåta kolonisering av Jupiters månar.
"Piecing things together after the event, we decided that the monolith was some kind of Sun-powered, or at least Sun-triggered, signaling device. The fact that it emitted its pulse immediately after sunrise, when it was exposed to daylight for the first time in three million years, could hardly be a coincidence.
"Yet the thing had been deliberately buried - there's no doubt about that. An excavation thirty feet deep had been made, the block had been placed at the bottom of it, and the hole carefully filled.
"You may wonder how we discovered it in the first place. Well, the object was easy - suspiciously easy - to find. It had a powerful magnetic field, so that it stood out like a sore thumb as soon as we started to conduct low-level orbital surveys.
"But why bury a Sun-powered device thirty feet underground? We've examined dozens of theories, though we realize that it may be completely impossible to understand the motives of creatures three million years in advance of us.
"The favorite theory is the simplest, and the most logical. It is also the most disturbing."You hide a Sun-powered device in darkness - only if you want to know when it is brought out into the light. In other words, the monolith may be some kind of alarm. And we have triggered it.