A PhD student thinks he's deciphered a 900-year-old carving that has long puzzled experts—and it's basically a valentine. The carving appears to be based on a code that subs in numbers for runes and, when deciphered, reads "kiss me," Jonas Nordby from the University of Oslo has concluded, according to the Daily Mail. Nordby, who is the first person to study all the runic codes in Northern Europe, deciphered the scrap after cracking the similar—and more challenging—Jötunvillur code.
To decipher the Jötunvillur, Norby found a stick that two men had signed in both normal runes and code runes. He discovered that they were transposing the last sound of a rune's name—so instead of writing the "m" rune, which is "maor," they'd write the "r" rune, the Guardian explains. "The problem with this code system is that it is impossible to read because the code gives many possible solutions," he says. That's why he thinks the codes weren't secret messages, but learning tools and deliberately difficult puzzles. (Read more Vikings stories.)