#### Cosmic chronometers

The **cosmic chronometers** are cosmological probes to measure the expansion history of the Universe in a cosmology-independent way. First introduced by Jimenez & Loeb (2002), the basic idea is that the differential age evolution of very massive and passively evolving galaxies in a given redshift bin can be used to directly measure the Hubble parameter H(z)=-1/(1+z)dz/dt, without relying on any cosmological assumption apart from a FRLW metric. If you are using cosmic chronometer data, you will find in this **gitlab repository** the detailed recipes (with examples) on how to correctly estimate the covariance matrix for cosmic chronometers (taken from Moresco et al. (2020)).