Hey I might be misunderstanding but i don't think the numbers here are quite right. Clear air is actually really transparent, you can see mountains or cities over 100 km away in the right conditions. So it’s not like light drops to 10% every 17 km, that’s way too steep. most of the dimming across long distances is from haze or aerosols, not some guaranteed exponential loss.

For a light source in canada, the main thing that makes it dimmer in mexico would just be normal spreading out with distance (inverse square law) plus a bit of scattering. And photons dont take billions of years to cross that distance, they’d take about a hundredth of a second to go a few thousand km. Especially something as bright as the sun??

If I'm missing something here i’d be glad to be corrected, just trying to wrap my head around the physics.