If you can crack this riddle without looking it up I will give you brainliest. You see a boat filled with people. You look again, but this time you don't see a single person on the boat. Why?

I had to pick a subject so just to let you know this is not arts.

because they are couples

Explanation:

photography had emerged as an elite art pursued by a few creative individuals for a few wealthy patrons. but now, said bauldelaire, it was succumbing to "the great industrial madness of our times." it was becoming a mass production industry that catered to middle-class tastes, including a taste for gadgetry. the stereoscope, the first 3d imaging system, had turned looking at photographs into parlor entertainment. a "thousand hungry eyes were bending over the peepholes of the stereoscope as though they were the attic-windows of the infinite.