The cosmological constant (Λ) is a term in Einstein’s field equations of general relativity that represents the energy density of empty space, also known as dark energy. Originally introduced by Einstein to allow for a static universe, he later called it his “biggest blunder” after the discovery that the universe is expanding.
However, the accelerating expansion of the universe, discovered in the late 1990s, brought the cosmological constant back into prominence. It is now understood as a possible explanation for dark energy, the mysterious force driving galaxies apart faster and faster over time.
Key features of the cosmological constant:
- It has a repulsive gravitational effect, counteracting gravity on large scales.
- It contributes to about 70% of the total energy content of the universe.
- It is uniformly distributed in space and does not dilute as the universe expands.
While Λ is a simple and widely used model for dark energy, its exact nature remains one of the greatest mysteries in physics and cosmology. It challenges our understanding of vacuum energy, quantum field theory, and the ultimate fate of the universe.