> cosmology hasn't accounted for differences in clocks given how central GR is to astronomy Of course it has. Yes, LCDM's FLRW metric, by its defining assumpti

> cosmology hasn't accounted for differences in clocks given how central GR is to astronomy Of course it has. Yes, LCDM's FLRW metric, by its defining assumption of spatial homogeneity, doesn't allow the metric (let alone the speed of clocks) to vary spatially. However, it is very common to do perturbation theory on top of the FLRW metric to account for density fluctuations. Besides, there are also models like LTB (Lemaître-Tolman-Bondi) which give up on homogeneity at the non-perturbative level (while still preserving isotropy, though). All in all, the idea that local voids could explain away the Lambda in LCDM is anything but new. It's just that the OP's timescape approach is the first one that seems to produce promising results. (Disclaimer: I merely skimmed the paper.)