wrote: "what are your thoughts on the recent timescape model news cycle, if you don't mind me asking."
This is the sort of pop science news I tend to ignore, because the pop descriptions make no sense and I figure if there's anything solid behind it I'll eventually hear about it from actual scientists, explained in a way I can understand.
But just for fun I'll see what Wikipedia says:
https://en.wikipedia.org/wiki/Inhomogeneous_cosmology#Timescape_cosmology
"In 2007, David L Wiltshire, a professor of theoretical physics at the University of Canterbury in New Zealand, argued in the New Journal of Physics that quasilocal variations in gravitational energy had in 1998 given the false conclusion that the expansion of the universe is accelerating."
So why the new hype?
"One more important step being left out of the standard model, Wiltshire claimed, was the fact that as proven by observation, gravity slows time. Thus, from the perspective of the same observer, a clock will move faster in empty space, which possesses low gravitation, than inside a galaxy, which has much more gravity, and he argued that as large as a 38% difference between the time on clocks in the Milky Way and those in a galaxy floating in a void exists."
Bwahaha! There's no way it could be that much. The rate of time when you're sitting on a massive spherical object is about sqrt(1 - rₛ/r) the usual rate of time, where rₛ is the radius of a black hole of that mass and r is the actual radius of that object. For a neutron star rₛ/r ≈ 1/2 so this is about 70%, i.e. time is slowed by roughly 30%. But the Milky Way is not nearly compressed enough for sort of effect to be significant (even near the middle).
(1/2)
Matt McIrvin (npub12gn…d572)
