The universe is expanding faster than theory predicts – physicists are searching for new ideas that might explain the mismatch

The James Webb Space Telescope's deep field image shows a universe full of sparkling galaxies. NASA/STScI

Astronomers have known for decades that the universe is expanding. When they use telescopes to observe faraway galaxies, they see that these galaxies are moving away from Earth.

To astronomers, the wavelength of light a galaxy emits is longer the faster the galaxy is moving away from us. The farther away the galaxy is, the more its light has shifted toward the longer wavelengths on the red side of the spectrum – so the higher the “redshift.”