The summer solstice is culture and science all wrapped up in one.

For some, it's a day to dress up in your "Silver Lake Shaman" best and throw a party. To science types, it's technically the days when our planet's rotational axis is most inclined toward the sun. In the Northern Hemisphere, that happens every year on June 20-21 while in the Southern Hemisphere, it's Dec. 20-21.

In the U.S., the summer solstice is largely an unofficial holiday. But in many countries, like Sweden, it's a time for love. "A lot of children are born nine months after Midsummer in Sweden," according to Swedish ethnologist Jan-Ă–jvind Swahn.

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