In general relativity, the presence of matter (energy density) can curve spacetime, and the path of a light ray will be deflected as a result. This process is called gravitational lensing and in many cases can be described in analogy to the deflection of light by (e.g. glass) lenses in optics. Lensing measures all the mass, in particular the dark matter as well as the luminous matter.
There are ongoing searches to use lensing to find a type of dark matter called MACHOs (massive compact halo objects). Although MACHOs, as dark matter, cannot be seen themselves, if they pass in front of a source (e.g. a star nearby), they can cause the star to become brighter for a while, e.g. days or weeks. This effect has been observed but determinations of the dark matter are not yet conclusive.
Based on a text by Joanne Cohn.
Artist's impression showing the approximate extent of the dark matter halo around a large spiral galaxy such as our own (Credit: Jose Wudka)
3D map of the universe's dark matter (Credit: NASA, ESA and R. Massey)
Gravitational lensing caused by dark matter (Credit: NASA)
Dark Matter #02, 2009
The works of Dennis Feddersen truly occupy space. He experiments with different types of materials. Flexibility is one of the most important criteria for his choice of materials, thus emphasizing the possibilities that may arise during the creative process. He constantly adjusts his flexible sculptures in a series of trials: i.e. he reacts to the surrounding architecture and adapts his sculptures accordingly.
Check this illuminating video about dark matter and gravitational lensing.