## Hubble Constant

Observing gravitational waves

### Expansion of the Universe

Image credit: NASA / JPL-Caltech

Determining the Hubble constant from gravitational wave observations with LISA.

The Hubble constant describes the expansion rate of the Universe. By observing gravitational waves from Extreme Mass Ratio Inspirals (EMRIs), see also chapter Testing General Relativity and Galactic census, LISA will allow to determine the Hubble constant with unprecedented precision.

With two years of observation LISA can measure the Hubble constant more accurately than any present method, and with a comparable accuracy to that expected from other future space missions.