Cosmological horizons

Abstract

The recently unveiled deep-field images from the James Webb Space Telescope have renewed interest in what we can and cannot see of the universe. Answering these questions requires understanding the so-called "cosmological horizons" and the "Hubble sphere". Here we review the topic of cosmological horizons in a form that university physics teachers can use in their lessons, using the latest data about the so-called standard "Lambda Cold Dark Matter" ($\Lambda$CDM) model. Graphical representations are plotted in terms of both conformal and proper coordinates as an aid to understanding the propagation of light in the expanding universe at various epochs.