The velocity of the universe refers to the expansion of the universe, which is typically measured in terms of the recessional velocity of distant galaxies. However, it's important to note that the concept of "acceleration" in the context of the entire universe is a bit more complex and not directly applicable in the same way as it is for objects within a localized system.
The expansion of the universe is governed by a parameter known as the Hubble constant (H₀), which represents the rate of expansion. Its current accepted value is around 70 km/s per megaparsec (km/s/Mpc). This means that for every megaparsec of distance between two objects, the recessional velocity between them increases by approximately 70 km/s.
Acceleration, on the other hand, represents a change in velocity over time. In the case of the universe's expansion, the rate of expansion, or the Hubble constant, is essentially a measure of the "velocity per unit of time." Therefore, there is no straightforward way to determine the acceleration of the universe from just the given velocity of 70 km/s. It requires a more complex understanding of the cosmological models and parameters involved.
It's worth noting that the expansion of the universe is believed to be accelerating due to the presence of dark energy, a hypothetical form of energy that permeates space and exerts a negative pressure. This acceleration is usually represented by the parameter known as the cosmological constant (Λ) or dark energy density. However, the specific value of this acceleration depends on the overall cosmological model being considered and the precise measurements of various cosmological parameters.