Two of the greatest mysteries in physics—dark matter and extra dimensions—may turn out to be connected. A new study suggests that the properties of this invisible substance are determined by a hidden fifth dimension. As a result, it interacted actively in the early Universe but later became almost undetectable by instruments.
Gravity Without Light
Dark matter neither emits nor absorbs anything, so it cannot be observed directly. Its presence is revealed only through gravity. It prevents galaxies from flying apart and also bends light from distant objects, an effect known as gravitational lensing.
According to estimates, there is approximately five times more of this invisible mass in the Universe than ordinary matter. At the same time, its particles pass freely through planets and stars without leaving any trace.
Extra Dimensions
This does not refer to parallel universes from science fiction. Physicists mean directions that are compactified to microscopic scales and are therefore imperceptible in everyday experience.
The idea itself has a century-long history. As early as the 1920s, Theodor Kaluza and Oskar Klein attempted to unify gravity with electromagnetism by adding a fifth coordinate to spacetime. String theory, the most widely known modern extension of physics, requires at least 11 dimensions.
Dark Photons and Resonance
Along with dark matter, another component may exist in the fifth dimension, as reported by Space.com. This is the dark photon, a hypothetical carrier of a separate interaction, similar to a particle of light.
The geometry of this additional space arranges the masses of dark matter particles into a particular sequence. This creates a resonance similar to the intense vibration of a musical instrument at certain notes.
An Explanation for the Early Universe
According to study co-author Yu-Dai Tsai of the University of Sheffield, the resonance could have greatly enhanced dark matter interactions during crucial periods of cosmic history, particularly shortly after the Big Bang. At the same time, the approach explains why dark matter appears inert today and why it is so difficult to detect.
Previous similar models treated this phenomenon as an ad hoc assumption without deeper justification. The authors of the new study derived it directly from the geometry of hidden dimensions.
As a result, physicists now have specific targets for future searches for the invisible substance. The findings were published in the peer-reviewed journal Physical Review D.
