I don't want to check miles, but it's pretty on point with what I remember, which is the horizon being 5km away for a 180cm (~6ft) tall person. (3 miles is close enough to 5km)
Getting even a few meters of something under you would drastically change how far you see.
1.8 meters sees ~4.8km. Standing on top of a car, on someone else's shoulders, at say, 5 meters, would give you eight kilometers.
Granted, not too drastic yeah. But like, if you have a tree, and climb it, and it's, say, 15 meters. Now you can see ~14 kilometers.
I'd say going from ~5 to ~14 by climbing a tree (or a mast of a ship) is pretty significant, but not drastic, I'd agree to that, yeah.
I wonder how much it was an advantage at sea, really. Like the scout at the top of your mast would be able to see the enemy ship from very far, while the enemies would technically be able to see only the mast of the ship that the scout is on, making it much harder to spot. I'm sure someone's written about it in tedious length. An upvote to anyone who finds me such texts.
Before you can look where? It turns out the damn tower doesn't even have windows! You can see nothing but walls and your stupid boomer mom screaming you're a disappointment!
(Last week I had this, just not in a windowless tower. Fucking boomers)
Light emitted farther than 46 billion light years away will never reach you. While traveling an infinite distance the universe expands faster, and light emitted not that far will get so red-shifted that it won't be visible anymore.