The conservation of angular momentum is said to be due to the isotropy of space and the conservation of energy is due to the homogeneity of time. How do conservation laws then apply to space and time in a gravitational field and is this strictly observer dependent?

You'll get various answers to this. Some will say energy is not conserved, whilst I say it is. I imagine most people will say angular momentum is conserved, whilst I say it isn't.

I say that because the "coordinate" speed of light at the event horizon, as measured by distant observers, is zero. And nothing can move faster than light, so at that location, any rotation rate has to be zero too. This doesn't sit too well with the

Kerr Metric, but what can I say?

Note that in his

Leyden Address Einstein described a gravitational field as a place where space is

*"neither homogeneous nor isotropic"*.