> A single variable being different for each galaxy isn't a problem per se. As John von Neumann said: With four parameters I can fit an elephant to a curve.

> A single variable being different for each galaxy isn't a problem per se. As John von Neumann said: With four parameters I can fit an elephant to a curve. With five I can make him wiggle his trunk One parameter can do a lot of work. And whether or not astrophysicists are right about dark matter, they’re certainly very very smart and good at math.