Researchers at the University of Waterloo used a technique known as weak gravitational lensing to create a composite image of the bridge. Gravitational lensing is an effect that causes the images of distant galaxies to warp slightly under the influence of an unseen mass, such as a planet, a black hole, or in this case, dark matter.
Very cool stuff. I wish this kind of thing was applauded more than some new app produced for easier product consumption. People go where the money is, etc.