In the search for a cosmological model that perfectly explains our universe, most astronomers invoke the notion of dark matter. But what if they should instead modify the age-old laws of gravity? In the first of a three-part series, Keith Cooper explores the struggles and successes of modified gravity in explaining phenomena at varying galactic scales, as well as matching observations from the cosmic microwave background
Imagine if, in one fell swoop, with one small tweak to the laws of gravity, you could wave away the need for all the dark matter in the universe. You’d rid yourself of a pesky particle that is only inferred to exist and has so far defied discovery. Instead, you would replace it with an elegant theory that modifies the fundamental work of Isaac Newton and Albert Einstein.
At least that’s the dream of modified Newtonian dynamics, or MOND. Developed by Israeli physicist Mordehai Milgrom and Mexican-born American-Israeli theorist Jacob Bekenstein in the early 1980s, it was their antidote to the popular “dark matter” paradigm. To them, dark matter was an unnecessary and clumsy bolt-on to cosmology that, if real, means that 80% of the matter in the cosmos is invisible.
In the 40 years since it was devised, MOND’s achievements continue to be overshadowed by cosmology’s love affair with dark matter. MOND has also struggled to explain phenomena at scales larger and smaller than individual galaxies. So is MOND something we should be taking seriously after all?
To read more, click here.