In 1961, mathematician and metereologist Edward Norton Lorenz was running some weather simulations. He noticed that by altering the starting conditions of a simulation by a nearly imperceptible amount, the end results would be drastically different.
Since then, many other occurrences of this phenomenon have been observed.
In space, with satellites and the Kessler Syndrome. In Cybersecurity, with the Avalanche Effect, which is leveraged to keep your data safe. In nuclear explosions and in continent-wide blackouts.
Your whole life might be forever ruined or forever improved by this effect, and you'd never know.