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Why Do Flocks of Geese Fly in a “V” Shape?

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In large swaths of the U.S. this time of year, it seems you can’t get more than a few feet without tripping over a Canada Goose; they come down here from the Great White North for the winter months (or, in some places, hang out year-round). When they’re not lounging about in field and stream, you might see them flying overhead, usually in a large "V" formation, with one bird in the lead and the others trailing behind it in two diverging lines.

Why do they fly in a “V”? Not just because a “Q” would be too hard. Scientists have found that the “V” formation serves two functions that make group travel easier.

Give Me A Lift

One reason—first proposed by aerospace engineers Peter Lissaman and Carl Shollenberger in 1970—is that the shape of the formation makes the birds more energetically efficient flyers than they would be flying alone. As a goose flies, air rushes around its wings, creating circular, rotating patterns of air at the ends of the wings called wingtip vortices. The vortices push air downward and upward in different spots (you can see a pretty clear illustration of this here), and if another goose is flying in one of the spots where the air is getting pushed up, it gets some free lift (the air force that directly opposes the goose’s weight) from the efforts of the first goose.

If geese fly in a group and arrange themselves correctly, then every one behind the leader gets a little extra lift and doesn’t have to flap as much to maintain altitude and forward momentum. The less they flap, the more energy they conserve, and the farther they can fly.

For a long time, scientists only had mathematical models, photos and distant observations of live geese to support this idea. The aerodynamics made sense, and observed birds were almost always in positioned in the formation to gain some advantage, but no one was able to directly measure the energetic benefit, if any, to free-flying birds.

Then, in 2001, French scientists had a unique opportunity to do just that when they crossed paths with a film company that had trained great white pelicans to fly in formation behind motorboats and ultralight planes for movie scenes. Researchers from the Centre d'Etudes Biologiques de Chizé, led by ecologist Henri Weimerskirch, fitted the birds with heart rate monitors and then filmed them in flight. Their data showed that the heart rates of pelicans flying in “V” formation were 11.4–14.5 percent lower than that of any one bird flying alone, and that the birds in formation could afford to flap less and glide more, for energy savings of 11.4–14.0 percent.

Given this, why don’t all birds fly in the “V”? It seems the advantages of the formation only apply to larger birds, like geese and pelicans, and aren’t as pronounced for smaller, lighter birds. But other formations may have their benefits, too. While the “cluster” formations that pigeons fly in, for example, actually cost them energy versus flying alone, they might allow large groups to fly close together and maneuver and turn without mid-air collisions.

An Eye On You

Researchers have noticed something funny with some bird flocks: While the birds usually fly in positions that give them some energy benefit, not every bird is always in the expected optimal position, and therefore they get lower energy savings. Some birds just aren’t making the most of the “V,” which got people thinking that there might be another reason for the formation.

That reason might be that the formation allows the birds to maintain visual contact with each other and to communicate, making it easier to keep the group together and navigate. Taking the angles of the formation and what they know about geese’s field of vision and “blind spots” into account, researchers from the University of Rhode Island hypothesize that a “V” angle of 29 degrees or more would allow every bird in the group to see every other bird. There don't appear to be any studies that directly test this idea.

Just like with the energy conservation idea, though, the birds don’t always take up the optimal spot for clear visual contact. Most fly, instead, in positions that give them some benefit in terms of both energy and flock contact, or in one or the other. Those close-but-no-cigar situations beg the question of whether there's another "V" advantage we're not seeing, or if it's just really hard for birds to find and maintain the best spot in the formation.

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Big Questions
How Long Could a Person Survive With an Unlimited Supply of Water, But No Food at All?
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How long could a person survive if he had unlimited supply of water, but no food at all?

Richard Lee Fulgham:

I happen to know the answer because I have studied starvation, its course, and its utility in committing a painless suicide. (No, I’m not suicidal.)

A healthy human being can live approximately 45 to 65 days without food of any kind, so long as he or she keeps hydrated.

You could survive without any severe symptoms [for] about 30 to 35 days, but after that you would probably experience skin rashes, diarrhea, and of course substantial weight loss.

The body—as you must know—begins eating itself, beginning with adipose tissue (i.e. fat) and next the muscle tissue.

Google Mahatma Gandhi, who starved himself almost to death during 14 voluntary hunger strikes to bring attention to India’s independence movement.

Strangely, there is much evidence that starvation is a painless way to die. In fact, you experience a wonderful euphoria when the body realizes it is about to die. Whether this is a divine gift or merely secretions of the brain is not known.

Of course, the picture is not so pretty for all reports. Some victims of starvation have experienced extreme irritability, unbearably itchy skin rashes, unceasing diarrhea, painful swallowing, and edema.

In most cases, death comes when the organs begin to shut down after six to nine weeks. Usually the heart simply stops.

(Here is a detailed medical report of the longest known fast: 382 days.)

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

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Big Questions
Why is Friday the 13th Considered Unlucky?
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Today, people around the globe will feel uneasy about getting out of bed, leaving their homes, or going about their normal daily routines, all because of a superstition. These unfortunate folks suffer from “paraskavedekatriaphobia,” a common neurosis familiar to us all: the fear of Friday the 13th. But just where did this superstitious association come from, and how did it catch on?

The truth is that no one is absolutely sure where the idea that Friday the 13th is unlucky originated. Donald Dossey, the founder of the Stress Management Center and Phobia Institute in Asheville, North Carolina, suspects the fear can be traced back to a Norse myth about 12 gods who had a dinner at Valhalla—the fabled hall where legendary Norse heroes feasted for eternity after they died—that was interrupted by a 13th guest, the evil and mischievous god Loki. According to legend, Loki tricked Höðr (the blind god of winter and son of Odin, the supreme god in Norse mythology) into shooting his brother Baldr (the benevolent god of summer who was also a son of Odin) with a magical spear tipped with mistletoe—the only substance that could defeat him. Thus the number 13 was branded as unlucky because of the ominous period of mourning following the loss of such powerful gods by this unwanted 13th guest.

For whatever reason, among many cultures, the number 12 emerged throughout history as a "complete" number: There are 12 months in a year, 12 signs of the zodiac, 12 Gods of Olympus, 12 sons of Odin, 12 labors of Hercules, 12 Jyotirlingas or Hindu shrines where Shiva is worshipped, 12 successors of Muhammad in Shia Islam, and 12 tribes of Israel. In Christianity, Jesus was betrayed by one of his 12 Apostles—Judas—who was the 13th guest to arrive for the Last Supper. Surpassing the number 12 ostensibly unbalances the ideal nature of things; because it is seen as irregular and disrespectful of a sense of perfection, the number 13 bears the stigma of misfortune and bad luck we know today.


Friday joins in the mix mostly because all of the early accounts of Jesus’s crucifixion agree that it took place on Friday—the standard day for crucifixions in Rome. As Chaucer noted in The Canterbury Tales, "And on a Friday fell all this mischance." Yet perpetuating Friday as an unlucky day in America came from the late 19th-century American tradition of holding all executions on Fridays; Friday the 13th became the unluckiest of days simply because it combined two distinct superstitions into one. According to the Oxford University Press Dictionary of Superstitions, the first reference to Friday the 13th itself wasn’t until 1913. (So despite actually occurring on Friday, October 13, 1307, the popular notion that the Friday the 13th stigma comes from the date on which the famed order of the Knights Templar were wiped out by King Philip of France is just a coincidence.)

The repercussions of these phobias reverberated through American culture, particularly in the 20th century. Most skyscrapers and hotels lack a 13th floor, which specifically comes from the tendency in the early 1900s for buildings in New York City to omit the unlucky number (though the Empire State Building has a 13th floor). Street addresses sometimes skip from 12 to 14, while airports may skip the 13th gate. Allegedly, the popular Friday the 13th films were so-named just to cash in on this menacing date recognition, not because the filmmakers actually believed the date to be unlucky.

So, is Friday the 13th actually unlucky? Despite centuries of superstitious behavior, it largely seems like psychological mumbo jumbo. (One 1993 study seemed to reveal that, statistically speaking, Friday the 13th is unlucky, but the study's authors told LiveScience that though the data was accurate, "the paper was just a bit of fun and not to be taken seriously." Other studies have shown no correlation between things like increased accidents or injuries and Friday the 13th.)

And Friday the 13th isn't a big deal in other cultures, which have their own unlucky days: Greeks and Spanish-speaking countries consider Tuesday the 13th to be the unluckiest day, while Italians steer clear of Friday the 17th. So today, try to rest a little easy—Friday the 13th may not be so unlucky after all.

Additional Source: 13: The Story of the World’s Most Popular Superstition.

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