A look at the Hubble speed from first principles

Understand

We introduce a novel way of measuring $H_0$ from a combination of independent geometrical datasets, with no need of calibration nor of the choice of a cosmological model.

• We build on the {\it distance duality relation} which sets the ratio of the luminosity and angular diameter distance to a fixed scaling in redshift for any metric theory of gravity with standard photon propagation and constitutes a founding block of any theory describing our Universe.
• Our method provides the unprecedented possibility of determining $H_0$ from first principles, unleashing the measurement of this fundamental constant from calibration and assumption of a cosmological model.
• We find $H_0=69.5 \pm 1.7$ km/s/Mpc at $68\%$ C.L.