The chapter gives an explanation for the ordinary and dark energy density of the cosmos. We present a connection between quantum entanglement and the absence of almost 95.5% of the energy supposed to be contained in the cosmos. The ordinary energy density is equal to half that of Hardy's quantum probability of entanglement ϕ⁵/2, where ϕ= 5-1/2. The reverse of quantum entanglement called quantum disentanglement is consequently one minus ϕ⁵, i.e., 1 -ϕ⁵. Dark energy density is given by one minus ϕ⁵ divided by two, i.e., 1-ϕ⁵/ 2=5ϕ². This result is in full agreement with the numerous previous theoretical predictions as well as being in remarkable agreement with the cosmic measurements and observations. The present chapter takes the view that our current mathematical knowledge and general theories are in position to explain ordinary energy, dark matter and pure dark energy both qualitatively and quantitatively.