Ever since humans gained the ability to look down at the Earth from
airplanes, space shuttles, and satellites, we've discovered a number of unusual markings. We know
very little about them.
This is a sketch of some mysterious lines that are found on the Nazca Desert of Peru. They stretch
for several miles, crossing over cliffs and hills.
A Swiss author named Erich von Daniken claims in his book,
Chariots of the Gods, that these lines were made by aliens who
visited the Earth long ago. A German scientist, Maria Reicher, says that von Daniken's idea is
ridiculous, and she has her own theory.
What do you think? Can you imagine how and why an alien visitor might have made these
marks? How might humans have made them—and for what reason(s)?