?? how gimbal picture of b2 relates to penrose diagrams ... ?? ...

?? schubert singularity .... light cone .... one light-beam away ... ?? in gimbal picture one of the schubert varieties as hopefully obviously non-singular ??? .....

?? b2 apartment ... weyl group dihedral ... flipping gimbal over along either of 2 orthogonal axises ... ?? ...

?? how to understand "other" a2 in g2 ... other ball, i mean .... ?? maximal compact of split form .... ???? ..... root system pattern ... real forms ... ?? separating out the long root subalgebra ... ??? .....