There is too much bad news to justify complacency. There is too much good news to justify despair. - Donella Meadows

A quantity growing exponentially toward a limit reaches that limit in a surprisingly short time.

In physical, exponentially growing systems, there must be at least one reinforcing loop driving growth and at least one balancing feedback loop constraining growth, because no system can grow forever in a finite environment.

The least obvious part of a system, its function or purpose, is often the most crucial determinant of the system's behavior.