Arman Shafieloo

A distant lamp shines through uneven glass. The glass bends the rays, and instead of one flame on the wall, several appear — some brighter, some fainter. In much the same way, a massive galaxy bends the light of an exploded star. There was one explosion, but the images show four glowing points.

The Universe is expanding faster and faster thanks to mysterious dark energy, discovered in the late 1990s by Adam Riess, Saul Perlmutter, and Brian Schmidt using supernovae.

Since the late 20th century, astronomers have known that the recession of galaxies is accelerating, as if pushed by an invisible tailwind.

The cosmological standard model is like a recipe for a cake where everything is strictly measured: dark matter is like flour without a single lump (zero pressure), and dark energy is like the perfect leavening agent (equation of state exactly minus one). But what if the flour is a bit damp and the leavening agent has lost its oomph?