This document discusses geysers and how to predict the eruption schedule of Old Faithful geyser. It explains that geysers consist of a reservoir, opening, heat source, and underground channels. Eruptions occur when water in the reservoir becomes so hot it expands into steam. This triggers a chain reaction that ejects water and steam through the opening. After eruptions, the reservoir refills until the next eruption. The document also presents a linear equation and data table showing that the duration of an eruption correlates to the time until the next eruption, allowing one to predict Old Faithful's schedule based on the prior eruption length.