Can clumpy matter fool us into seeing dark energy change over time?

Using supercomputer simulations of cosmic structure, researchers asked whether local clumps of matter could trick observers into measuring a false evolution of dark energy. They traced light paths through realistic universes where dark energy is actually constant, then measured what different observers would infer about its properties. One observer in twenty saw the DESI signature of changing dark energy—suggesting the real signal might owe more to our cosmic neighborhood than to fundamental physics.