This is the second in a collection of notes by Egan on the physics of his Orthogonal trilogy (which I&#x27;ve just started, but which seems excellent as always).  It may make more sense to start with the first, <a href="http:&#x2F;&#x2F;gregegan.customer.netspace.net.au&#x2F;ORTHOGONAL&#x2F;00&#x2F;PM.html" rel="nofollow">http:&#x2F;&#x2F;gregegan.customer.netspace.net.au&#x2F;ORTHOGONAL&#x2F;00&#x2F;PM.ht...</a> .