How Do Fireworks Get Their Colors?

deymos, iStock / Getty Images Plus
deymos, iStock / Getty Images Plus

Want to impress your friends while you wait for this year’s fireworks display to begin? Wow them with your knowledge of basic chemistry and let them in on the secrets to the rainbow beauty of the night sky on the Fourth of July.

Small pellets, charmingly named "stars," are the key to the fireworks's colors, EarthSky reports. The stars are filled with different combinations of metal salts that each add a bright color to the firework when it explodes.

Different chemical elements correspond with different colors: strontium carbonate for red, calcium chloride for orange, sodium nitrate for yellow, barium chloride for green, and copper chloride for blue. Purple fireworks are created much like you might create purple paint—by mixing red and blue.

According to LiveScience, when you light the fuse on the outside of the fireworks's thick tube, the flame ignites a pouch of black powder inside known as the lift charge, which causes the shell containing the stars to catapult into the air. As it rises, a time-delay fuse begins to burn within it and, by the time it reaches its maximum height, the shell bursts, causing the stars inside to color each strand of the explosion.

Paul Nicholas Worsey, fireworks expert and professor of mining and nuclear engineering at the University of Missouri at Rolla, told LiveScience that red and green are the easiest colors to create, while blue is more difficult. Worsey says gold is best if you want your firework to keep its color for a long time, maybe even until it hits the ground.

The trick behind those especially crowd-pleasing fireworks that change color after they explode is simple: The stars are simply coated in multiple metal salts. Once you see the firework’s second color, that means the stars burned through their outer layer and reached a different metal salt—kind of like licking a Gobstopper.

For another way to impress your friends this fireworks season, learn the names of these 10 fireworks effects so you can call them out as they burst.

[h/t EarthSky]

Why You Should Never Charge Your Phone in Public USB Ports Without a USB Data Blocker

Creative-Family/iStock via Getty Images
Creative-Family/iStock via Getty Images

The USB charging ports that have popped up at airports, coffee shops, and even outdoor stations around cities in recent years are definitely a lifesaver when your smartphone is down to its last bit of juice. A dead phone is annoying at best and downright dangerous at worst, so it’s totally understandable why you’d jump at the chance to revive it at your earliest opportunity.

However, those public ports might not be as benevolent as they seem. According to Afar, hackers can load malware onto those stations—or on the cables left plugged into the stations—which can then deliver passwords and other data right from your device to the hacker’s. If you have used a public port recently, don’t panic; TechCrunch reports that these cases are fairly rare. Having said that, it’s definitely better not to risk it, especially considering what a nightmare it would be to have your identity stolen.

The Los Angeles County District Attorney’s Office explains that the easiest way to prevent becoming a victim of this type of scam, often referred to as juice-jacking, is simply to abstain from using public USB charging ports. Instead, invest in a portable charger, or plug your own charger into an actual AC power outlet.

But unoccupied power outlets are notoriously hard to come by in public places, and portable chargers themselves can also run out of battery life. Luckily, there’s a small, inexpensive device called a data blocker that will enable you to use public USB charging ports without worrying about juice-jacking. It looks a little like a flash drive with an extra slot, but it lacks the two wires usually found in USB chargers that can download and upload data. That way, your device will charge without transferring any information.

You can get two of them for $11 from Amazon here.

[h/t Afar]

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The Ingenious Reason Medieval Castle Staircases Were Built Clockwise

Shaiith/iStock via Getty Images
Shaiith/iStock via Getty Images

If you’re a fan of Game of Thrones or medieval programs in general, you’re probably familiar with action-packed battle scenes during which soldiers storm castles, dodge arrows, and dash up spiral staircases. And, while those spiral staircases might not necessarily ascend clockwise in every television show or movie you’ve watched, they usually did in real life.

According to Nerdist, medieval architects built staircases to wrap around in a clockwise direction in order to disadvantage any enemies who might climb them. Since most soldiers wielded swords in their right hands, this meant that their swings would be inhibited by the inner wall, and they’d have to round each curve before striking—fully exposing themselves in the process.

Just as the clockwise spiral hindered attackers, so, too, did it favor the castle’s defenders. As they descended, they could swing their swords in arcs that matched the curve of the outer wall, and use the inner wall as a partial shield. And, because the outer wall runs along the wider edge of the stairs, there was also more room for defenders to swing. So, if you’re planning on storming a medieval castle any time soon, you should try to recruit as many left-handed soldiers as possible. And if you’re defending one, it’s best to station your lefties on crossbow duty and leave the tower-defending to the righties.

On his blog All Things Medieval, Will Kalif explains that the individual stairs themselves provided another useful advantage to protectors of the realm. Because the individual steps weren’t all designed with the same specifications, it made for much more uneven staircases than what we see today. This wouldn’t impede the defenders, having grown accustomed to the inconsistencies of the staircases in their home castle, but it could definitely trip up the attackers. Plus, going down a set of stairs is always less labor-intensive than going up.

Staircase construction and battle tactics are far from the only things that have changed since the Middle Ages. Back then, people even walked differently than we do—find out how (and why) here.

[h/t Nerdist]

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