Dark energy is one of those cosmological features that we are still learning about. While we can't see it directly, we can most famously observe its effects on the Universe - primarily how it is causing the expansion of the Universe to speed up. But recently, physicists have begun to question even that narrative, pointing to results that show the expansion isn't happening at the rate our math would predict. In essence, dark energy might be changing over time, and that would have a huge impact