Time-Delay Cosmography: Measuring the Hubble Constant and other cosmological parameters with strong gravitational lensing

Understand

Multiply lensed sources experience a relative time delay in the arrival of photons.

• This effect can be used to measure absolute distances and the Hubble constant ($H_0$) and is known as time-delay cosmography.
• The methodology is independent of the local distance ladder and early-universe physics and provides a precise and competitive measurement of $H_0$.
• With upcoming observatories, time-delay cosmography can provide a 1% precision measurement of $H_0$ and can decisively shed light on the current reported 'Hubble tension'.