Dark Energy
An unknown form of energy with negative pressure that permeates all space and drives the accelerated expansion of the universe.
Governing formula
Ω_Λ ≈ 0.68, w = P / ρ ≈ -1
SI unit
Cosmological Constant Λ (J/m³)
In depth
Constitutes approximately 68% of the total universe energy density. Discovered in 1998 via Type Ia supernova distance observations. Modeled mathematically as the Cosmological Constant Λ in Einstein's field equations.
Examples in the real world
Distant Type Ia supernovae appearing dimmer than expected in a decelerating universe, confirming accelerated expansion.