# Why is expansion speeding up?

**Why is the expansion of the universe speeding up?**

Observations of distant supernovae in the late 1990s showed the expansion accelerating. The cause is called dark energy, which is a name for what is not yet understood.

Connects to:
- [The expanding universe](https://mapideas.org/i/as_expansion)

Sources:
- [Wikipedia: Dark energy](https://en.wikipedia.org/wiki/Dark_energy)

Source: https://mapideas.org/i/q_astro_faster · open on the map: https://mapideas.org/#q_astro_faster