Descriptions of most astronomical objects such as planets, stars and galaxies usually include how far away from Earth they are. The quoted distance may involve millions of kilometres, light years or parsecs.
Last month, we discussed astronomers' principles and methods to measure distances across space.
This evening we briefly review those in the context of their ideal range before discussing the cosmic distance ladder as a tool to optimise precision over extra-large distances. We then cover the current expansion of space, known as Hubble's constant (H0), in the context of "late-time" and "early-time" measurements, highlighting a severe discrepancy between the two, known as the Hubble Tension.
Two case studies illustrate using the cosmic distance ladder, with one showing the Hubble Tension, while another offers a solution.
