LIGO Long

This is one of two 4 km arms of the Hanford Laser Interferometer Gravitational-Wave Observatory (LIGO) located in the high desert of the Washington state Hanford Reservation (WWII bomb making). The concrete enclosure pictured protects a metal tube under vacuum through which a laser is bounced off a mirror at the opposite end. Results are compared between arms and with two other observatories (USA and Italy) to detect about 3 events a week. The first detection resulted in a Nobel prize. I had to take this at sun noon to the north due to restrictions on walking around.