Ask Ethan: Do galaxies appear larger in the past?

We know, instinctively, that when we see something that appears small in our field of vision, there are multiple possibilities. It could be an intrinsically small object that’s close by, a medium-sized object that’s an intermediate distance away, or a very large object that’s a large distance away. It’s why a bird, a plane, and the Moon can all appear to be the same size in our field of vision, taking up the same angle on the sky — what astronomers refer to as angular diameter — despite their vastly different intrinsic sizes. It’s simple geometry: an object twice as far away appears to have half the size, and apparent size decreases as distance increases. But that’s assuming that the geometry of the Universe is fixed, grid-like, and Euclidean. In our actual, expanding Universe, things aren’t so simple, and that’s why Doug Plata writes in to ask about how Andromeda, or an Andromeda-sized galaxy, would appear to us if we viewed it at different epochs throughout cosmic history: <a href="https://medium.com/starts-with-a-bang/ask-ethan-do-galaxies-appear-larger-in-the-past-6cfafb617ae2">Website</a>