A New Cosmic Tension: The Universe Might Be Too Thin

Cosmologists have concluded that the universe doesn’t appear to clump as much as it should. Could both of cosmology’s big puzzles share a single fix?

The cosmos is starting to look a bit weird. For a few years now, cosmologists have been troubled by a discrepancy in how fast the universe is expanding. They know how fast it should be going, based on ancient light from the early universe, but apparently the modern universe has picked up too much speed — a clue that scientists might have overlooked one of the universe’s fundamental ingredients, or some aspect of how those ingredients stir together.

Now a second crack in the so-called standard model of cosmology may be forming.