I know why i think it, flying at 70000 feet, clear to the eye. Ok ok so this could be faked? Then hundreds of thousands of other images will also be faked? sure thing!:
If it were a conspiracy it would be on an immeasurable scale involving thousands of scientists and government personnel. Put simply, it's impossible. Twats.
Unless you have flown via concorde or in high-altitude military jets, you cannot possibly have seen the curvature of the Earth. Even if the Earth was round, you would have to be at an altitude way above that used by commercial airliners today to observe the Earth's curvature. I think 60,000 feet is the approximate figure given, but I'm not sure.
Needless to say, that means you definitely cannot observe said curvature from the beach. That's not just the viewpoint of Flat Earth Theory; RE scientists will tell you the same thing.
Simplistic observation. You fail at it. Ever watched a sailing ship as it goes directly out towards the horizon? The ship line slowly dissapears until only the sails can be seen. It's something that has been observed for hundreds of years. Even taking a strong telescope and watching it, it still happens, so it can't be down to distance and the ship looking smaller.