Fish don't know about water, because they don't know about anything else. Water is everything to them. No alternative could occur to them even if they were capable of rational thought because no alternative has ever been experienced. Rudyard Kipling put it another way: Who knows England, who only England knows?
We live in our time - no other time is available to us. It is to us as the water is to the fish. We cannot truly see it or understand it, still less record it with any accuracy because we can't seize time and inspect it, we can't do anything except notice the symptoms or symbols of our time and remark on them. And even that is difficult. As Mao Tse Tung said when asked about the effects of the French Revolution, "It is too soon to tell." What makes our time different in the truest sense from any other? How do our feelings about common phenomena compare to those of the Romans, for instance, or Regency Britain? Don't we just assume they are the same throughout time?
Here are some things that we take utterly for granted and which may, over time, change or disappear for ever. Romantic love; motherhood; money; international trade; holidays; unrestricted travel; political freedom. Loss of any one of these is almost unthinkable, but nearly all of them are recent and artificial constructs when set against human history. They appeared, and they can disappear. The exception is motherhood, which although a fundamental throughout time, could become victim to as yet distant technological changes.
There is another category of change to which we might - almost certainly will - be subject: the currently Unimaginable. Many people have tried to imagine the future but few have got even close, and most of them have seen it in terms of contemporary circumstances extrapolated. But it only takes a brief inspection of the recent history of mankind to see that how we live now would have been completely at variance to the imaginings of our forebears only a few hundred years ago. Even Leonardo only imagined discrete manifestations of a future technology.
So, some things we take for granted will disappear over time and others, whose current absence we also take for granted, will be introduced, although we can have no idea what they will be.
And this relates to photography, how?