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" References to Friday as an unlucky day first appeared in Western literature in the 17th Century\u2014any business conducted or jobs, journeys and harvests begun were ill-fated. And it is believed that the number came to represent bad luck because that&amp;#039;s how many people sat at the table of the Last Supper\u2014and the first to leave died soon afterward. Combine the two, say the superstitious, and something very bad is bound to happen. Today is Friday the 13th\u2014that irregular holiday of superstitions\u2014and, to celebrate, we&amp;#039;re taking a closer look at those everyday household happenings turned supernatural that the old wives blame for bad luck. It&amp;#039;s hardly 9/11 or Katrina, but this is Popular Mechanics, and we like to debunk things. Plus, it&amp;#039;s still Friday, and we like to have a little fun. So I asked some of PM&amp;#039;s expert editors\u2014and drew on my own experience\u2014to prove, once and for all, that the myths of Friday the 13th are pure poppycock.   Walking Under a Ladder Many believe that because ladders form the shape of a triangle, they are representative of the Holy Trinity\u2014and that walking through it, which is equal to breaking the Holy Trinity, puts you in league with Beelzebub. But according to Senior Home Editor Roy Berendsohn, walking under a ladder is nothing more than a physical danger. &amp;quot;If someone is high up on an extension ladder and you walk between it and the house, you might get a tool dropped on your head,&amp;quot; he says, &amp;quot;but you won&amp;#039;t be cursed for life.&amp;quot; And since people know there&amp;#039;s a risk of injury by falling wrench, it seems silly to blame fate, luck or lack thereof. Try stupidity instead. Crossing Paths with a Black Cat Cats may be aloof, snooty and bad-tempered, but they certainly aren&amp;#039;t evil. Long ago, cats were associated in Egypt with religion and elsewhere with witchcraft but why black cats in particular are assumed to be bad luck remains somewhat of a mystery. &amp;quot;It&amp;#039;s really just a genetic quirk,&amp;quot; says Senior Science Editor Jennifer Bogo. &amp;quot;Cats are black because they carry two recessive genes\u2014not because they&amp;#039;re from the dark side. In fact, black cats can actually be lucky, because by mapping the cat genome we can learn about human disease.&amp;quot; In my own experience, black cats are a joy to own, and while the felines themselves seem to have misfortune aplenty (They&amp;#039;re tough to see at night, and I grew up in a house next to a major road. Capeesh?), they haven&amp;#039;t brought me any. Not Leaving the Embers Burning It&amp;#039;s been said that if you completely put out a fire before you go to bed, you&amp;#039;ll hit an unfortunate streak. But Berendsohn begs to differ: &amp;quot;That comes from an era before matches and other means of rapidly re-lighting a fire.&amp;quot; While it&amp;#039;s okay to leave embers smoldering, he says, &amp;quot;You don&amp;#039;t want to have live embers in a fireplace and turn in for the night without thoroughly protecting the hearth area using a fire screen. That way, if an ember pops and shoots some sparks, it&amp;#039;s intercepted by the screen.&amp;quot; When camping, Berendsohn insists, even the superstitious need to take a walk on the wild side. &amp;quot;You never leave a[n outdoor] fire with live embers\u2014ever. The fire is doused, raked around to be sure there are no active glowing members. Ideally, the ashes and coals are covered with dirt before departing.&amp;quot; Ironically or not, Friday the 13th this year also falls in the middle of Fire Prevention Week. Breaking a Mirror The first mirror-makers were the ancient Romans, who believed that glass reflected a person&amp;#039;s soul. They also believed that life renewed itself every seven years, so breaking a mirror\u2014and, thus, your soul\u2014meant seven long years of misery. But a more likely culprit for any ill health following a shattering is mercury, which was used in mirrors until the 1800s. &amp;quot;Mercury is a neurotoxin\u2014it affects the nervous system,&amp;quot; Bogo says. &amp;quot;Mercury poisoning can lead to madness; that&amp;#039;s the big one. It can also damage the nerves and the kidneys, cause gingivitis and affect the development of infants and children.&amp;quot; Thankfully, the element is no longer used to make mirrors, rendering this myth moot. Spotting a Bat at Home While some might consider having a bat perched peacefully somewhere in your house bad luck in and of itself, superstition would have us believe that having the creepy creatures flying around brings on even more misfortune. It&amp;#039;s a good thing I didn&amp;#039;t know that when I was 13 and woke up to a bat winging its way around my room, disoriented because of the daylight but otherwise nonconfrontational. As I huddled under the covers with my (black) cat, Shadow, I might have been helplessly frightened, but I wasn&amp;#039;t unlucky\u2014then, or in the days following, or at all. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/science/environment/a951/4199622/>