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LIGO is a virtual organization with a concrete goal (discovering gravitation gravitational waves) and specific large equipment (the detectors) to help reach that goal. LIGO, however, is not a uniform, flat organization. Within LIGO, there are several smaller organizations. These smaller organizations have specific needs regarding how new people join in their groups, and yet, these smaller organizations all have something in common - the parent organization of LIGO, where access to the equipment and the data is controlled, where agreements may be signed with new organizations wanting to be a part of (or a partner of) LIGO.
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