1. The Origin of the Cosmological Constant
In 1917, Einstein introduced the cosmological constant (Λ) into his equations to counteract gravity’s pull and keep the universe static—an idea widely accepted at the time.
However, in 1929, Edwin Hubble’s observations revealed that the universe was actually expanding, not static.
With this discovery, Einstein considered Λ unnecessary, calling it a mistake. Yet, this discarded concept would eventually resurface as scientists explored deeper cosmic mysteries.