>1. The distance traveled by a photon going through a fiber optic cable will be different from the distance through the ground.
it is still shorter than through the satellite. Also the fiber distance difference can be measured and accounted for - much simpler than to account for satellite position.
But they're not bouncing photons up to and down from a GPS satellite; they're only using GPS for clock synchronization and measuring the distance, which is accurate to a lot less than the distance light travels in 60ns.
>But they're not bouncing photons up to and down from a GPS satellite; they're only using GPS for clock synchronization
by noting photons coming from GPS when neutrinos start at CERN and when neutrinos reach Gran Sasso. 2 downward legs (actually 3 as the photons at the start of neutrino run need to be noted at both points) instead of 1 upward and 1 downward that would constitute proper "bouncing" - i don't see much difference to warrant specific term in this case than talking about general approach of racing the neutrinos against photons.
Compare to running through a fiber, which length (only 700km) and speed of light inside it can be easily accounted for, with GPS we have photons coming from the 12K miles distance (in the best case, ie. when the satellite is right overhead) which is measurable much less precisely than the fiber on the ground and these photons are coming through the atmosphere conditions of which (specifically speed of light in it) are much less precisely known than about the same fiber on the ground.
>and measuring the distance, which is accurate to a lot less than the distance light travels in 60ns.
until they used the military GPS they would have positioning error in the Earth surface tangential plane of a few feet at least (say 2 feet though it would be an extremely small error). Using 20000km/700km proportionality of that triangle, 2 feet on tangential plane would mean ~60 feet in GPS signal arrival precision, ie. 60ns+ of time of flight (it is of course oversimplification, only to demonstrate the scale of imprecision inherently present in the scheme with satellite flying over at 20K km)
Very interesting reading btw, especially on atmospheric and Stagnac effect errors :
it is still shorter than through the satellite. Also the fiber distance difference can be measured and accounted for - much simpler than to account for satellite position.