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Why Is Soda Measured in Liters?

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Never a nation to fall in line, America is one of the few countries to resist the metric system. We stubbornly measure distance in miles and weight in pounds. So what’s with those two-liter bottles of soda?

First, a clarification: Soda is far from the only substance we measure in metric units. Heck, it’s not even the only beverage. Wine, liquor, and bottled water are sold by the milliliter. The healthcare field is all about metric units, too, from cholesterol levels to prescription, over-the-counter, and supplement dosages. We run 5-kilometer races, ride on 215-millimeter tires, and use 8-millimeter cameras, or at least we used to.

In most other things, we determinedly cling to our imperial measurements. Attempts to convince Americans to join the rest of the metric-measuring world have been met with great resistance.

Ken Butcher of the National Institute of Science and Technology has been working with the government’s tiny Metric Program for years. Speaking to Mental Floss back in 2013, Butcher explained that we’re so entrenched in our way of doing things that switching measurement systems now would be both chaotic and expensive.

"If we were going to start a new country all with the metric system, it would be easy," he said. "But when you have to go in and change almost everything that touches people’s everyday life and their physical and mental experience, their education, and then you take that away from them—it can be scary."

Here and there, though, when it’s convenient, we have been willing to budge. The soda bottle is a good example. Until 1970, all soft drinks in the U.S. were sold in fluid ounces and gallons, mostly in glass bottles. Then the plastic polyethylene terephthalate (PET) bottle came along, and soft drink makers decided it was time for a product redesign.

The redesign process coincided with two key factors: a short-lived wave of government interest in going metric, and the burgeoning environmental movement.

The folks at PepsiCo decided to meld all three into its exciting new vessel: a lightweight, cheap, recyclable, metric bottle, with built-in fins so it could stand up on supermarket shelves. Two liters: the soda size of the future.

The two-liter bottle took off. The rest of the soft drink world had no choice but to get on board. And voila: liters of cola for all.

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Where Did the Myth That Radiation Glows Green Come From?
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by C Stuart Hardwick

Probably from radium, which was widely used in self-luminous paint starting in 1908. When mixed with phosphorescent copper-doped zinc sulfide, radium emits a characteristic green glow:


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The use of radioluminescent paint was mostly phased out by the mid-1960s. Today, in applications where it is warranted (like spacecraft instrument dials and certain types of sensors, for example), the radiation source is tritium (radioactive hydrogen) or an isotope of promethium, either of which has a vastly shorter half life than radium.

In most consumer products, though, radioluminescence has been replaced by photoluminescence, phosphors that emit light of one frequency after absorbing photons of a difference frequency. Glow-in-the-dark items that recharge to full brightness after brief exposure to sunlight or a fluorescent light only to dim again over a couple of hours are photoluminescent, and contain no radiation.

An aside on aging radium: By now, most radium paint manufactured early in the 20th century has lost most of its glow, but it’s still radioactive. The isotope of radium used has a half life of 1200 years, but the chemical phosphor that makes it glow has broken down from the constant radiation—so if you have luminescent antiques that barely glow, you might want to have them tested with a Geiger counter and take appropriate precautions. The radiation emitted is completely harmless as long as you don’t ingest or inhale the radium—in which case it becomes a serious cancer risk. So as the tell-tale glow continues to fade, how will you prevent your ancient watch dial or whatever from deteriorating and contaminating your great, great grandchildren’s home, or ending up in a landfill and in the local water supply?

Even without the phosphor, pure radium emits enough alpha particles to excite nitrogen in the air, causing it to glow. The color isn’t green, through, but a pale blue similar to that of an electric arc.


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This glow (though not the color) entered the public consciousness through this early illustration of its appearance in Marie Curie’s lab, and became confused with the green glow of radium paints.

The myth is likely kept alive by the phenomenon of Cherenkov glow, which arises when a charged particle (such as an electron or proton) from submerged sources exceeds the local speed of light through the surrounding water.

So in reality, some radionuclides do glow (notably radium and actinium), but not as brightly or in the color people think. Plutonium doesn’t, no matter what Homer Simpson thinks, unless it’s Pu-238—which has such a short half life, it heats itself red hot.


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

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How Are Royal Babies Named?
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After much anticipation, England's royal family has finally received a tiny new addition. The birth of the Duke and Duchess of Cambridge's second son was confirmed by Kensington Palace on April 23, but the name of the royal newborn has yet to be announced. For the heir to the British throne and his wife, choosing a name for their third child—who is already fifth in line to the throne—likely won't be as easy as flipping through a baby name book; it's tradition for royals to select names that honor important figures from British history.

According to ABC WJLA, selecting three or four names is typical when naming a royal baby. Will and Kate followed this unwritten rule when naming their first child, George Alexander Louis, and their second, Charlotte Elizabeth Diana. Each name is an opportunity to pay homage to a different British royal who came before them. Some royal monikers have less savory connotations (Prince Harry's given name, Henry, is reminiscent of a certain wife-beheading monarch), but typically royal babies are named for people who held a significant and honorable spot in the family tree.

Because there's a limited pool of honorable monarchs from which to choose, placing bets on the royal baby name as the due date approaches has become a popular British pastime. One name that keeps cropping up this time around is James; the original King James ruled in the early 17th century, and it has been 330 years since a monarch named James wore the crown.

If the royal family does go with James for the first name of their youngest son, that still leaves at least a couple of slots to be filled. So far, the couple has stuck with three names each for their children, but there doesn't seem to be a limit; Edward VIII, who abdicated the throne to George VI in 1936, shouldered the full name of Edward Albert Christian George Andrew Patrick David.

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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