Doubting Dark Matter

An alternative to the hidden sector of physics

This simulation shows a map of dark matter. The haunting black filaments represent the dark matter itself while the spectacles of light are normal (or baryonic) matter. Image by Tom Abel & Ralf Kaehler.

There is a hidden sector in physics. It’s a precarious area of science, dealing with undetected quantum fields and their particles which, if we could observe just once, would explain phenomena like dark matter, particle anomalies, and aspects of string theory. Some of the members of the hidden sector may even sound familiar — axions, sterile neutrinos, and dark photons. And while they would be illuminating, they’re not susceptible to the strong, weak, or electromagnetic forces, making them less able to interact with everyday visible matter. The hidden sector, then, is made up of hypothetical particles that could flood the space around us in their own secretive dance, revealing in that choreography answers to questions we’ve been studying for decades. And yet throughout the decades every carefully constructed and expensive experiment has failed to produce evidence that they exist.

The alternative solution is not to look for new particles, but to modify the laws of gravity.

We evoke dark matter to explain the motions of stars and galaxy clusters. With the amounts of normal matter in our universe and with our current laws of physics, stars at the fringes of their galaxies should move slower because they’re further away from the galaxy’s center of mass. And yet they move at the same…