In the 1930s, Fritz Zwicky noticed that galaxies in clusters were moving way too fast — visible matter couldn't hold them. Later, Vera Rubin confirmed this for individual galaxies. Thus, dark matter was born. By the end of the 20th century, supernova explosions revealed that cosmic expansion is accelerating, and Adam Riess got a Nobel Prize for it — cue dark energy.

A new model replaces both with a single elastic substance — a cosmic jelly. In the young Universe, it was soft, gathering gas into galaxies and acting like dark matter. Over time, the jelly firmed up and now pushes everything apart, speeding up expansion (like dark energy). This stiffness dampens pesky wobbles that made earlier models unstable.

An unexpected bonus: in this medium, gravitational waves acquire a tiny mass, as if sound grew heavy in Jell-O. Spotting the effect isn't easy, but future telescopes can test other predictions, like a subtle “slip” in gravity. If confirmed, the dark sector would turn out to be a single whole.