Einstein's cosmological constant

Einstein's cosmological constant is a term he introduced in his equations of General Relativity to allow for a static universe. At the time, he believed the universe was unchanging. This constant represented a force that counteracted gravity, preventing the universe from collapsing. Later, when it was discovered that the universe is actually expanding, he called it his "greatest blunder." Today, the cosmological constant is linked to dark energy, which is thought to drive the accelerated expansion of the universe, making it a crucial concept in modern cosmology.