# What is driving the expansion of the Universe?

1. Is it just the momentum from the Big Bang? If yes, how can it account for the acceleration of the expansion?
2. Why isn't the collective gravitational force slowing it down?
3. What part does dark energy play in the expansion?

As far as I understood it, no one really knows. It is observable that the universe is expanding with increasing speed, therefore there has to be a form of energy driving it. We can meassure (or at least try) the amount of energy and find $\Omega_\lambda = 69.11\%$ (see $\lambda$CDM-Model)