In a system modeling an input over time, a right-half-plane zero is when some exponential growth rate of the input has no effect on the output. For example, eating ice cream increases happiness but creates more unhappiness so you eat more ice cream to make up for it and so on until there is no ice cream anywhere.
A system with a right-half-plane zero needs to be carefully designed around because when subjected to an input it will have the inverse response first. For example, when a plane attempts to climb by pitching up, it initially moves down first. If the pilot over corrects by pitching up further, they will input will have no effect on the output and it will end up crashing.
- The Ringelmann effect shows groups become less productive as they grow
- A Mobius strip and Klein bottle are like physical/virtual representations of right-half-plane-zeros
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Adding new dependencies to a codebase is a net positive until it’s not. The added leverage of picking up an off-the-shelf solution eventually gives way to dependency hell—fixing breaking changes, incompatibilities between things, security issues, and so on.
Like the Mitch Hedburg joke, “when escalators break they become stairs—sorry for the convenience” reminds us about the importance of designing systems that fail gracefully. Escalators can still be used even when their function no longer works unlike elevators where you get stuck until it’s fixed.