Ball lightning is a well-known phenomenon. That is, it has been seen and described consistently by many people in many places, since the ancient Greeks. But after thousands of years, scientists still do not understand what causes ball lightning!
Pearls have long been considered a precious gem. They were presented as gifts to Chinese royalty as early as 2300 BCE! And we know they were used as adornment from ancient times because a fragment of pearl jewelry was found in a Persian princess’ sarcophagus dating to around 420 BCE.