What fraction of the universe is dark energy?

Observations indicate that dark energy constitutes roughly 68% of the total energy density of the universe.

Is the cosmological constant truly constant?

In the standard Lambda-CDM model it is. Some alternative theories propose a slowly varying dark-energy component called quintessence.

Although tiny per cubic metre, it fills all of space uniformly and has been driving accelerating expansion for billions of years.

Compute the dark-energy density of the universe from the cosmological constant and the speed of light using rho_Lambda = Lambda * c^2 / (8 * pi * G).

Cosmological Constant (Lambda)

1/m²

Dark Energy Density

0.000000000000000000000000005924 kg/m³

Energy Density (GeV/m³)3.323808 GeV/m³

Dark Energy Density vs Cosmological Constant (Lambda)

Dark energy drives the accelerating expansion of the universe. Its density is linked to the cosmological constant.

rho_Lambda = Lambda * c² / (8 pi G)

*Lambda* is the cosmological constant (~1.1 x 10⁻⁵² m⁻²)

*c* is the speed of light

*G* is the gravitational constant

The resulting density is extremely small but dominates the total energy budget of the cosmos.

Use the observed cosmological constant Lambda = 1.1056e-52 m⁻².