Why Do We Knock on Wood?

iStock / cagan
iStock / cagan

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.”

What Is the Shelf Life of Donated Eyes?

iStock.com/Pedro_Turrini
iStock.com/Pedro_Turrini

Zoe-Anne Barcellos:

I can only answer for cornea and eye donation.

The FDA does all oversight (no pun intended) of organ disposition.

The main organs—heart, liver, pancreas, lungs, etc.—are transplanted within hours. They are just not viable if they are not being perfused constantly.

The other tissues—like bone, skin, tendons, etc.—do not need to be transplanted immediately. But I am not sure on the regulations of when they need to be transplanted.

With the eyes, there are four tissues that can be recovered.

We recover whole eyes for research and education purposes. These usually go much faster, but we can hold them up to a year.

Conjunctiva can also be recovered; conjunctiva is a clear covering over most of the eye (it is what gets irritated when you have pink eye). I have been working as a recovery tech for five years, and our office has not had a request for "conj" in all that time. I believe it is mostly used for research, but I could be wrong.

Sclera is the white area of your eye. It is fairly thick and flexible. If you have ever touched a reptile egg, that is what it reminds me of. We recover sclera for transplant. They use it for several things, but mainly to patch punctures. Similar to if you pop the inner tube of your bike and repair it. Sclera can also be used to repair ear drums. We can hold on to this for up to a year.

The main thing we recover is corneas. In the U.S., we must transplant these within seven days of recovery. (Recovery is usually within hours of death, but we can push it up to 20 hours after if needed.) Sometimes we have more corneas than we need, and then they are shipped overseas and transplanted up to 14 days after recovery. There is no real different outcome with the later transplant time, but the FDA in the U.S. made the rules. (You can sign up to be an organ, tissue, and eye donor here.)

This post originally appeared on Quora. Click here to view.

Why Are There No Snakes in Ireland?

iStock
iStock

Legend tells of St. Patrick using the power of his faith to drive all of Ireland’s snakes into the sea. It’s an impressive image, but there’s no way it could have happened.

There never were any snakes in Ireland, partly for the same reason that there are no snakes in Hawaii, Iceland, New Zealand, Greenland, or Antarctica: the Emerald Isle is, well, an island.

Eightofnine via Wikimedia Commons // Public Domain

Once upon a time, Ireland was connected to a larger landmass. But that time was an ice age that kept the land far too chilly for cold-blooded reptiles. As the ice age ended around 10,000 years ago, glaciers melted, pouring even more cold water into the now-impassable expanse between Ireland and its neighbors.

Other animals, like wild boars, lynx, and brown bears, managed to make it across—as did a single reptile: the common lizard. Snakes, however, missed their chance.

The country’s serpent-free reputation has, somewhat perversely, turned snake ownership into a status symbol. There have been numerous reports of large pet snakes escaping or being released. As of yet, no species has managed to take hold in the wild—a small miracle in itself.

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