  We consider the spatial clustering of massive black hole (MBH) mergers, and
discuss possible ways to use gravitational wave observations in the LISA and
DECIGO/BBO range for obtaining cosmological and cosmogonical information.
Constraints on large scale structure (LSS) and merger histories may be possible
by detections of an alignment of the GW polarization direction with principal
axes of the LSS. Constraints on the merger physics and the reionization epoch
may be obtained by GW measurements of MBH correlation lengths, in the case when
the MBH angular momentum loss occurs through gas drag. Such measurements would
provide information about the LSS and the reionization epoch, additional to and
independent of any obtained from electromagnetic signals, as well as about the
astrophysics of MBH mergers.
