Readers have asked me if the “L4″ and “L5″ nodes in my ebook Glitch are real. Yes, indeed. They are Lagrange (or Lagrangian) points. Wikipedia has a technical article http://bit.ly/Dt8x on these nifty results of gravity in our solar system. Or try Jake Turk http://bit.ly/1c7PIkv for a narrative combination of history and physics. NASA already uses Lagrange points in space missions, so now you can watch for references to Lagrange points in the news
A contour plot of the effective potential of a two-body system. (the Sun and Earth here), showing the 5 Lagrange points. An object in free-fall would trace out a contour (such as the Moon, shown). (Photo credit: Wikipedia)