The tentative hypothesis could offer tantalizing new clues about the nature of dark energy, the mysterious force that physicists believe is responsible for the increasing speed at which the universe is expanding.

The theory that dark energy is responsible for accelerating the expansion of the universe was first proposed back in 1998, when researchers found that the amount of the mysterious force was fixed per unit of volume of space as a “cosmological constant.”.

Not all scientists fully subscribe to the theory though, as Nature points out, arguing instead that dark energy is made out of a “fifth element,” or what the researchers from the High Energy Accelerator Research Organization (KEK) in Japan and the Max Planck Institute for Astrophysics in Germany are now calling quintessence.

They suggested that by looking at maps of the cosmic microwave background (CMB) — the relic electromagnetic radiation left over from the early stages of the universe — scientists could theoretically look for certain light signatures to prove the quintessence theory.