Just go to the ocean, and watch a tall ship go beyond the horizon.
The bottom of the ship disappears as it follows the earth's curve, the top of the ship is the last you will see.
Of course, you need very good visibility to see it for the roughly 10 miles or more, because of local conditions.
Remember, surveying instruments use gravity to determine level. A bubble level at the equator and at the North or South poles will still show level, even though they point 90 degrees from the equator to the poles.
“watch a tall ship go beyond the horizon. “
Then break out the telescope or zoom lens and it’s back ... so ..how far before it really drops out of sight?
” use gravity to determine level.”
hmmm.... that’s something I never thought of .. so your saying that my level line actually curves with the curve ...
hmmm ... that still sort of twists my brain but it would explain the anomaly.
Now what about the picture from the moon?
keep going ... your doing good.