Waning Dark Energy May Evade ‘Swampland’ of Impossible Universes | Quanta Magazine

Since 1998 , we’ve known that the expansion of the universe is accelerating.

In the standard theoretical model of the cosmos, dark energy has a simple form: It is spread uniformly in space, maintaining a constant density at all times.

If dark energy is a cosmological constant, then the acceleration should hold steady.

But DESI ’s data set wasn’t big enough to test this by itself.

Dark energy's ultra-low density is a necessary condition for the existence of humans who ponder conundrums like this.

The value we observe in this universe, though minuscule, is about as big as it could be for galaxies to have formed before cosmic expansion stretched all matter apart.

Some cosmologists find that scenario implausible.

The theory posits that strings vibrate in 10 space-time dimensions — four of them big and six too small to see.

The geometric arrangement of the six imperceptibly small dimensions influences the amount of dark energy in the four -dimensional macroscopic realm we inhabit.

Hypothetical universes with properties that contradict string theory are dubbed “the swampland”.