Green screen?
Ai Time Drones.
They create the crop circles to mark the timeline, so that when the Ayys or Future Humans want to travel to a spot in time, if there is a documented Crop Circle, then it is safe to "travel" to that spot in time.
Heard that on Art Bell years ago.
It's good that he's gone. The politics would have gotten to him.
But it is uncanny of how much of that old Art Bell applies directly towards current events today.