In 1945 what had been part of the core territory of the state of Prussia was lost (so far irretrievably) by Germany and taken by Russia as a Baltic Sea port, the area of Kalingrad. What had been for hundreds of years the base of the German efforts to conquer the Baltic tribes was lost to Germany, and taken by their enemies the Russians, as a result of the defeat of Germany in World War II. One minute the people of Konigsberg were German citizens, and the next they were part of the Soviet Union, unwelcome in their own home city . Overnight it became a different world.
Wars are one aspect of life that makes places a different world. The city of Ayutthaya was once the capital of a splendid empire, and then it became ruins almost overnight when the Burmese sacked the city in 1767. We think our worlds are permanent, and then they change in the blink of an eye, because nothing we make will certainly endure, but all is subject to decay and oblivion, no matter how hard we try. And war is just one of the ways this may occur.
There are others. Natural disasters destroy civilizations that thought themselves permanent. No doubt the builders of Angkor and the great Mayan cities thought their work would endure, but the rain forest encroached on their cities and largely took them over, leaving future generations to forget that there ever had been a great civilization there. Nineveh, once the capital of a great and fearsome empire, was so completely destroyed that for centuries doubting historians thought the Bible was lying when they spoke of Assyria as a great empire. Today the Assyrians, or those who call themselves Assyrians, are a tiny minority in their own homeland, unable to protect themselves from oppressive regimes all around them.
Nor are material ruins the only things lost to time that make a world different. Civilizations write their exploits down on bas-reliefs or clay tablets and then no one is left to read their languages in a different world, so their exploits remain largely forgotten. This is not an isolated occurrence. Many civilizations (including relatively famous ones like the Etruscan and Easter Island ones) have many writings that remain totally obscure to this day because no one can read their language. Imagine if the fate of English being understood was my handwriting. That would be a scary thing.
The country singer Bucky Covington, a few years ago, released a popular single called “A Different World.” He and I are pretty similar in age, late generation Xers, and the world he described was my world, only a little bit less savage. Technology and changes in culture can make a world alien even over the course of a lifetime. It was a different life when horses were replaced by cars, when computers and the internet overtook the postal service and typewriters. Within a generation no one will probably know how to write cursive any longer except for a few holdouts and older people (even I myself, who learned it for years in school, write cursive only very poorly–while I am an extremely literate person in discourse, I am only marginally literate in the actual mechanics of writing).
Who knows what a different world we will see ourselves as time progresses. Will new technologies change the way we live our lives? Probably. Will social changes make obsolete that which we thought would never vanish? Probably. Will some war or calamity cause nations we thought would endure for centuries vanish into the rubbish bin of history? Almost certainly. Nothing in this world is permanent, and yet we give ourselves illusions that what we hold most dear will last forever, only to be rudely awakened when it has vanished like a cloud. Who knows what different worlds we will see; whether it is a privilege or a curse remains to be seen.