Does dark matter exist?

Well yes, but MOND is a humdinger of an alternative theory.

I’m not going to mislead you – many scientists wouldn’t give it the time of day, but it certainly is not a crackpot theory and is definitely worthy of my first blog post.

Dreamed up in 1983 to patch the rather embarrassing hole in our understanding of galaxy dynamics, MOND cheekily slips an extra term into Newton’s famous equation F=ma.

According to Newton, stars on the edge of a galaxy ought to orbit slower then the stars closer to the center. It was expected that these stars would act like our planetary neighbours who slow down as they get further from the sun. Mercury has the fastest velocity, and Pluto the slowest (yes we are keeping that dispossessed outcast in this blog post).

When they took a good look at the way stars move around galaxies, scientists found that this was not true. In fact velocity or the stars stayed constant as they went further from the center of the galaxy. They put this down to dark matter, that elusive stuff which we can’t quite detect. The skeleton in the astronomical cupboard which neatly solves and creates dilemmas.

MOND A.K.A. “Modified Newtonian dynamics” offers an alternate explanation. It sticks an extra term into Newton’s equation which comes into play in environments with low gravitational acceleration – like the deepest, darkest corners of space. This conveniently means that whilst it affects stars on the edge of galaxies, we can ignore it on earth as we are sit our humungous gravitational field.

It might seem too good to be true, but then again it should be – it was built bespoke for this picture.

Check out a 2001 paper about MOND here!