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CONTROL SYSTEMS 71
STAR Multiple
STAR Images
Bending Light
FIGURE 2-34 A gravitational lens.The path of light defines straight lines, so
gravity bends space.

around an intervening star in any direction (360 degrees), gravitational lenses often pro-
vide an image of a star as a ring or arc of light. Some nice examples of gravitational
lenses can be found at www.iam.ubc.ca/ newbury/lenses/glgallery.html.
The web page at http://imagine.gsfc.nasa.gov/docs/features/news/07nov97.html has
reported an extreme case of this effect as “a black hole that is literally dragging space
and time around itself as it rotates ...[in] an effect called frame dragging.”