Mathematics
The Method of Least Squares and Fitting a Line to Data
Quick fact
The method was developed independently by Carl Friedrich Gauss and Adrien-Marie Legendre in the early 1800s and was used to predict the orbit of the dwarf planet Ceres.
Why this is interesting
You have a scatter of points on a graph—how do you draw the 'best' straight line through them? There's a surprising mathematical answer that has powered science for over 200 years.