How Baryon Acoustic Oscillations Are Used to Measure the Expanding Universe

This Hubble diagram from the Dark Energy Spectroscopic Instrument (DESI) reveals a characteristic pattern — baryon acoustic oscillations, or BAO ‘bubbles’ — at different ages of the Universe. The amount of dark energy determines how fast the Universe grows, and therefore the size of the bubbles. The solid and dashed lines represent predictions of how big the bubbles will be depending on whether dark energy evolves with time or not. DESI will gather more data to determine which model is a better description of the Universe.