The Hubble Tension: Why Does the Universe Give Us Two Answers?

Astronomers have developed remarkably precise ways to measure how quickly the universe is expanding. There is just one problem. Measurements of the nearby universe produce one answer, while predictions based on the early universe produce another. The difference has survived years of improved observations and even a major cross check from the James Webb Space Telescope. Either an important source of measurement error remains hidden, or our standard description of cosmic history may be incomplete.