The Earth is concave. Don't transpacific cables travel less distance?
Also, light in fiber moves significantly slower than light in a vacuum (or even air). HFT has been utilizing that fact for a while now.
The distance in altitude does increase the length, but not by enough to negate the effect of the faster speed.
Across the pacific ocean?
You need to make up for the extra ~200 miles going up and down, as well as the extra curvature of the satellites orbital shell vs the ground. But, it is doable, assuming you can relay the signal fast enough from satellite to satellite. Fiber optics needs to also be boosted on long routes, I'm not sure how that affects latency. But at the very least, speed of light up/over/down is faster than .8C for 7000 miles around the earth
For what it’s worth, hollow core fiber is available now, although at least the one vendor I found is very very expensive. I haven’t found an entirely clear answer as to the group velocity in hollow core fiber (it’s not in the data sheets), but it ought to be pretty fast. (The group velocity in vacuum-filled waveguide is not the speed of light in a vacuum — it’s slower.)
https://www.linkedin.com/posts/stefanschlamp_cme-eurex-micro...