How Do Glowsticks Glow?

istock.com/setsukon
istock.com/setsukon

Picture an atom. Now picture that atom getting excited. Maybe its birthday is coming up. Anyway, when an atom or a molecule gets excited, its electrons' energy levels go up. When the electrons fall back down to their normal state, they release energy in the form of photons, a basic unit of light.

For most of the lights we make and use, those excited atoms release heat as well as light when they’re coming back down. Sometimes you want the latter without the former, a “cold light” like the kind made by fireflies. In the early 1960s, U.S. military and industry scientists knew that the key to making cold light on their own was chemiluminescence, the emission of light from chemical reactions. They just weren’t sure which materials and reactions they were after (luminol had been around for a little while, but had limited applications).

Edwin Chandross, a chemist at Bell Labs in Murray Hill, N.J., was one of the researchers working on the problem.

He wondered if peroxides – chemical compounds with an oxygen-oxygen single bond that could potentially liberate a lot of energy in some reactions - might do the trick. He tried a few experiments and found that hydrogen peroxide combined with oxalyl chloride and a fluorescent dye produced the cold chemical light he was after. The reaction’s efficiency was only about 0.1% (far short of fireflies’ near 90%), but it was a start.

Chandross began corresponding with Michael Rauhut at American Cyanamid in Stamford, Connecticut, and Rauhut’s team expanded on Chandross’ research, searching for ways to make the light bright enough for practical use. They eventually came up a diphenyl oxalate ester that reacted with hydrogen peroxide to make a bright light, trademarked their creation as Cyalume, and rolled it out on the market.

The reaction that happens inside a glowstick goes a little something like this:

- The typical glowstick contains an oxalate ester and dye solution within a plastic stick, and hydrogen peroxide within a small, fragile vial in the middle of the stick.

- When you bend the stick, the vial breaks open, and all the chemicals come together. The oxalate ester and hydrogen peroxide react, sometimes with the help of a catalyst, to form a peroxyacid ester and phenol.

- The peroxyacid ester decomposes to form more phenol and carbon dioxide, producing energy that excites all the molecules floating around in this little party, which then release photons, making the stick glow.

Since the glowstick’s invention, researchers have been fiddling around with this reaction, searching for fluorescing dyes to make different colors (green and yellow are said to be easy to make, while a good purple is near impossible) and adjusting the concentrations of the chemicals to brighten the glow or prolong its life.

American Cyanamid eventually sold its chemical light division, Omniglow. The R&D department there has continued to expand the uses and capabilities of glowsticks, creating luminescent intubating scopes and researching more efficient reactions and glow sticks that work at below-freezing temperatures.

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.

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

If March 15 Is the Ides of March, What Does That Make March 16?

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iStock.com/bycostello

Everyone knows that the soothsayer in William Shakespeare's Julius Caesar was talking about March 15 when he warned the Roman emperor to "beware the Ides of March." We also all know Caesar's response: "Nah, I gotta head into the office that day." But if March 15 is the Ides of March, what does that make March 16?

At the time of Caesar's assassination, Romans were using the Julian calendar (introduced by Julius Caesar himself). This was a modified version of the original Roman calendar, and it is very similar to the one we use today (which is called the Gregorian calendar). A major difference, however, was how Romans talked about the days.

Each month had three important dates: the Kalends (first day of the month), the Ides (the middle of the month), and the Nones (ninth day before the Ides, which corresponded with the first phase of the Moon). Instead of counting up (i.e., March 10, March 11, March 12), Romans kept track by counting backwards and inclusively from the Kalends, Ides, or Nones. March 10 was the sixth day before the Ides of March, March 11 was the fifth day before the Ides of March, and so on.

Because it came after the Ides, March 16 would’ve been referred to in the context of April: "The 17th day before the Kalends of April." The abbreviated form of this was a.d. XVII Kal. Apr., with "a.d." standing for ante diem, meaning roughly "the day before."

So, had Julius Caesar been murdered on March 16, the soothsayer's ominous warning would have been, "Beware the 17th day before the Kalends of April." Doesn't have quite the same ring to it.

This story first ran in 2016.

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