- #26

Hurkyl

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One model over which I've mulled is a conical universe. We can envision this universe as a cone in three dimensions (2 space and 1 time), with the axis of the cone being timelike.

It appears obvious that there is a distinguished class of observers on this cone: their worldlines are simply straight lines that originate from the vertex of the cone, and we can define an apparently universal intrinsic time coordinate by computing the proper time along these distinguished worldlines.

However, appearances are deceiving. There is actually a large class of observers -- you can start with

**any**geodesic eminating from the vertex that spirals around the cone, and get a similarly "distinguished" class of observers (geometrically, their worldlines are formed by rotating this first geodesic). These observers are

*also*moving "with the universal expansion", and their clocks will disagree with the clocks of the first class we noticed.