Einstein explained · 1917
Cosmological Constant
The cosmological constant, written Λ, is an extra term in Einstein's gravitational equations that can affect the large-scale behaviour of the universe.
Λ changes cosmic expansion
Λ COSMOS
What it means
The cosmological constant can act like a property of empty space. Depending on its value, it can influence how the universe expands.
Einstein's contribution
Einstein introduced the term in 1917 while trying to build a static model of the universe. He later abandoned that original purpose when an expanding universe became accepted.
Why it matters
The cosmological constant remains part of modern cosmology and is widely used in models of the accelerated expansion associated with dark energy.
Continue exploring
Einstein’s key theories and contributions
1905Special RelativityHow motion changes measurements of space and time while the speed of light stays constant.Read explainer →1905Mass–Energy EquivalenceWhy mass and energy are connected by Einstein's famous relation E = mc².Read explainer →1907Equivalence PrincipleWhy free fall and acceleration gave Einstein the starting point for a new theory of gravity.Read explainer →1907Gravitational RedshiftHow gravity changes the frequency of light and the rate at which clocks run.Read explainer →1916–1918Gravitational WavesHow changing masses can send ripples through spacetime at the speed of light.Read explainer →1915General RelativityHow Einstein described gravity as curved spacetime shaped by matter and energy.Read explainer →1916–1917Quantum Theory of RadiationHow atoms absorb and emit light, including Einstein's prediction of stimulated emission.Read explainer →