I live in New York City, a place full of people (tourists and non-tourists) taking photos. Every time I bike over the Brooklyn Bridge, as hundreds of tourists take selfies and panoramas, I’m in the background. As people take photos of each other—of Lake Louise, of the White House, of a Bloody Mary at brunch—other people end up in the frame. But how many? How many photographs out there feature you or me in them, in the background, beneath the Eiffel Tower or at the table next to the birthday party? Is it 100? 1,000? 5,000? 10,000? More?

This might seem like a ridiculous question. But theoretically, we’re not far off from a future in which companies using facial-recognition technology could tag you in all those pictures. In fact, Facebook can recognize you in photos even if your face isn’t in them—using what it knows about your body type, your clothes, and your posture.

But right now, actually figuring out how many pictures exist of any one person in the world is probably impossible. Even trying to find someone, anyone, to help me think through this question was a bit like an academic game of hot potato. Every scholar, historian, and academic I contacted referred me to someone else, who then referred me to someone else, who sometimes referred me back to the first person, and so on.

So, it’s tough even to estimate, but bear with me as I try.