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Why Do We Knock on Wood?

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Reader Dante wrote in to ask, “Why is knocking on wood good luck?”

Traditionally, when you speak of your own good fortune, you follow up with a quick knock on a piece of wood to keep your luck from going bad. More recently, simply saying the phrase “knock on wood”—or “touch wood” in the UK—has replaced actually knocking. Where’d all this come from?

Before Christianity and Islam came around to spoil the party with their rules about idolatry, many pagan groups and other cultures—from Ireland to India to elsewhere in the world—worshipped or mythologized trees. Some peoples used trees as oracles, some incorporated them into worship rituals and some, like the ancient Celts, regarded them as the homes of certain spirits and gods.

Authors Stefan Bechtel and Deborah Aaronson both suggest two connections between knocking on wood and these spirits in their respective books, The Good Luck Book and Luck: The Essential Guide.

The first possible origin of knocking on wood is that it's a much more laid-back version of the ruckus that pagan Europeans raised to chase away evil spirits from their homes and trees or to prevent them from hearing about, and ruining, a person’s good luck.

The other origin they suggest is that some of these tree worshippers laid their hands on a tree when asking for favor from the spirits/gods that lived inside it, or did it after a run of good luck as a show of gratitude to the supernatural powers. Over the centuries, the religious rite may have morphed into the superstitious knock that acknowledges luck and keeps it going.

“In either case, you are seeking protection against envy and anger,” Bechtel and co-author Laurence R. Stains* write. “The envy of evil spirits and the anger of the gods, who take a dim view on mortals bearing too much pride and who get especially annoyed when they're responsible for your run of good luck and you're not grateful.”

*Mentalfloss.com deputy editor Erin and I both took journalism classes with Larry in college, but I didn’t know he’d written this book until I started working on this post. Small world, huh? 

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Big Questions
What's the Difference Between Vanilla and French Vanilla Ice Cream?
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While you’re browsing the ice cream aisle, you may find yourself wondering, “What’s so French about French vanilla?” The name may sound a little fancier than just plain ol’ “vanilla,” but it has nothing to do with the origin of the vanilla itself. (Vanilla is a tropical plant that grows near the equator.)

The difference comes down to eggs, as The Kitchn explains. You may have already noticed that French vanilla ice cream tends to have a slightly yellow coloring, while plain vanilla ice cream is more white. That’s because the base of French vanilla ice cream has egg yolks added to it.

The eggs give French vanilla ice cream both a smoother consistency and that subtle yellow color. The taste is a little richer and a little more complex than a regular vanilla, which is made with just milk and cream and is sometimes called “Philadelphia-style vanilla” ice cream.

In an interview with NPR’s All Things Considered in 2010—when Baskin-Robbins decided to eliminate French Vanilla from its ice cream lineup—ice cream industry consultant Bruce Tharp noted that French vanilla ice cream may date back to at least colonial times, when Thomas Jefferson and George Washington both used ice cream recipes that included egg yolks.

Jefferson likely acquired his taste for ice cream during the time he spent in France, and served it to his White House guests several times. His family’s ice cream recipe—which calls for six egg yolks per quart of cream—seems to have originated with his French butler.

But everyone already knew to trust the French with their dairy products, right?

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
How Many Rings Does Saturn Have?
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Of all the planets surrounded by rings, Saturn is the most famous. These planetary rings are massive enough that Galileo was able to see them using a simple telescope way back in 1610, though it wasn't until half a century later that another scientist was able to figure out what the "arms" Galileo saw actually were. NASA has since called them "the most recognized characteristic of any world in our solar system."

So how many rings does Saturn have, anyway? If you can see them from your backyard, there must be a lot, right?

Scientists don't know for sure exactly how many rings Saturn has. There are eight main, named ring groups that stretch across 175,000 miles, but there are far more than eight rings. These systems are named with letters of the alphabet, in order of their discovery. (Astronomers have known about ring groups A, B, and C since the 17th century, while others are newer discoveries. (The most recent was just discovered in 2009.)

The rings we can see in images of the planet—even high-resolution images—aren't single rings, per se, but are in fact comprised of thousands of smaller ringlets and can differ a lot in appearance, showing irregular ripples, kinks, and spokes. The chunky particles of ice that make up Saturn's rings vary in size from as small as a speck of dust to as large as a mountain.

While the gaps between Saturn's rings are small, the 26-mile-wide Keeler Gap is large enough to contain multiple moons, albeit very small ones. The largest ring system—the one discovered in 2009—starts 3.7 million miles away from Saturn itself and its material extends another 7.4 million miles out, though it's nearly invisible without the help of an infrared camera.

Researchers are still discovering new rings as well as new insights into the features of Saturn's already-known ring systems. In the early 1980s, NASA's Voyager missions took the first high-resolution images of Saturn and its rings, revealing previously unknown kinks in one of the narrower rings, known as the F ring. In 1997, NASA sent the Cassini orbiter to continue the space agency's study of the ringed planet, leading to the discovery of new rings, so faint that they remained unknown until Cassini's arrival in 2006. Before Cassini is sent to burn up in Saturn's atmosphere in September 2017, it's taking 22 dives through the space between the planet and its rings, bringing back new, up-close revelations about the ring system before the spacecraft dives to its death.

Though it's certainly possible to see Saturn's rings without any fancy equipment, using a low-end telescope at your house, that doesn't mean you always can. It depends on the way the planet is tilted; if you're looking at the rings edge-on, they may look like a flat line or, depending on the magnification, you might not be able to see them at all. However, 2017 happens to be a good year to see the sixth planet, so you're in luck.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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