The Virgo gravity-wave interferometer, an €80-million (US$114-million) experiment located near Pisa, Italy, has been incapacitated by a vacuum failure for most of the summer and is expected to stay out of commission for another few months.

During a test on 9 May a glass viewport in the L-shaped detector shattered, sending shards of glass into one of the laser-reflecting mirrors and its ancillary instrumentation. The mirror was damaged beyond repair and is being replaced.

The team has decided to replace all 100 viewports to avoid another failure. Francesco Fidecaro, Virgo's spokesman, who is a physicist at the University of Pisa, says the original viewports might not have been "appropriate" for the operating conditions. Physicists believe that it was not the vacuum itself but the vibrations created by the pumps that caused the port to fail. They are confident that the new viewports will not fail in the same way.