It is commonly said that we cannot have infinite growth on a finite planet. This this is clearly understood, at least intellectually, by most people. The implications and consequences, however, are often ignored. On the one hand, we have physical limits imposed by the planet that prevent infinite expansion, and on the other we have only a finite amount of resources, especially energy, without which continued growth cannot be maintained.
Our current economic system, which is primarily measured in terms of GDP, depends on continual growth, year after year, over time. There can be temporary periods of economic contraction, which are called recessions or depressions, and are something to be avoided as much as possible. Interestingly, contraction is often referred to as "negative growth", which reinforces the idea of how much the idea of "growth" is implicit within the system. Other than these temporary setbacks though, for the system to survive, a long term trend of increasing growth is required.
