The secret marriage
by Martina Matijević
of dark matter and fifth force.
A matter of fact?
Scientists from Université de Genève and collaborators performed one of the most precise tests of whether dark matter behaves like ordinary matter by comparing galaxy motions within cosmic gravitational wells to the predicted depth of those wells.
Their observations showed that dark matter falls into these wells exactly as expected under standard gravity, allowing no measurable deviations. Because any additional “fifth force” acting on dark matter stronger than about 7% of gravity would have altered galaxy velocities in detectable ways, the researchers conclude that if such a force exists, it must be weaker than that threshold.
Further reading:
‘Dark matter acts surprisingly normal in a new cosmic test’, 2025, Université de Genève, ScienceDaily, available: https://www.sciencedaily.com/releases/2025/11/251115095924.htm
‘Comparing the motion of dark matter and standard model particles on cosmological scales’, 2025, Grimm, N., et al., Nature Communications, http://dx.doi.org/10.1038/s41467-025-65100-8
Author bio:
Martina Matijević is a poet from Croatia who has traveled around the Sun 24 times, which makes her 24 years old in Earth’s timekeeping. Her work has been featured in Modern Haiku, Frogpond, Kokako, The Cold Moon Journal, Acorn, and others. You can discover more of her poetry here: https://tinamatijev.wixsite.com/martina-matijevi