When you buy through links on our articles, Future and its syndication partners may earn a commission.An illustration of tendrils of dark matter stretching across the cosmos. | Credit: RubinObs/NOIRLab/SLAC/NSF/DOE/AURA/J. Pinto, CC BY 4.0Scientists have discovered that dark matter, the universe’s most mysterious “stuff,” obeys gravity on vast cosmological scales. This could help to dismiss the possibility of a fifth fundamental force of nature — but even if not, it certainly puts restraints on that potential force’s strength.It’s long been known that “everyday matter” is made up of atoms, which are, in turn, composed of protons, neutrons and electrons. We also know that these particles fall in line with the known fundamental forces of nature: electromagnetism, gravity, the strong nuclear force and the weak nuclear force. However, what has been less clear is whether dark matter obeys these same four forces. Indeed, one of the reasons dark matter is so puzzling is that it doesn’t seem to act in conjunction with light, or electromagnetic radiation. And if it does, it does so much more weakly than ordinary matter does. This makes dark matter effectively invisible, meaning the only way scientists can infer its presence is by observing its gravitational effects and then watching how that acts as a middleman and impacts light and ordinary matter.AdvertisementAdvertisementBut determining that dark matter interacts gravitationally on relatively small scales, such as within galaxies, doesn’t tell us if it obeys the well-understood laws of gravity as defined by Albert Einstein’s 1915 theory of gravity, general relativity, on much larger cosmological scales. That is a big question because accounting for five times more of the matter in the universe than everyday matter, dark matter should have played a major role in how the cosmos developed.To solve this conundrum and to discover if dark matter could be governed by a fifth, thus far unknown fundamental force, researchers from the University of Geneva (UNIGE) set about determining if dark matter falls into cosmic gravity wells on vast scales just as ordinary matter does. These gravity wells are created when bodies of tremendous mass cause the very fabric of space and time, unified as a single four-dimensional entity called “spacetime,” to warp (as established by general relativity). The greater the mass of the body, the more extreme the warping of spacetime, the “deeper” the resultant gravity well, …
