The Color Of A Fire Hydrant Means Something To Firefighters
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Despite popular belief, not all fire hydrants are red. In fact, to a firefighter, red is the last thing they should be. That's because in parts of the U.S. and Canada, the color of a fire hydrant—or, specifically, its top and nozzle cap—is usually a sign of its flow rate and water pressure. This lets firefighters know whether a particular hydrant will provide them with the amount of water they'll need to put out the fire they're facing. It also tells them what size hose to use, how best to pump the water, and a variety of other essential information. A blue top means that the hydrant will produce a great flow—at least 1,500 gallons per minute. Green means the hydrant will produce slightly less, orange less than that, and red means the hydrant will produce less than 500 gallons per minute, which is probably not enough to get the job done. These colors are laid out in a National Fire Protection Association standard known as NFPA 291. But this is just a recommendation, and as a result, not all municipalities or fire departments follow it. In fact, individual state and city regulations sometimes piggyback or contradict the regulation, leading to problems. For example, a Texas law requires all "nonfunctioning" fire hydrants—that is, ones that pump less than 250 gallons per minute—to be painted black. Many rural areas can't necessarily guarantee a dependable flow rate, so they end up painting all of their hydrants black to avoid liability, leaving firefighters unable to tell them apart. Learn more about fighting fires with the videos below.
What Stuntmen Go Through Before Being Set On Fire
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Being a stuntman is not just as simple as being brave. Professional stunt people must have very athletic backgrounds (usually with a history of gymnastics practice)-and that's even before taking all the steps to become one. It's an extremely demanding and dangerous gig that usually runs in the family, so it's already hard to break into. There are stunt schools you can attend, and you must also join the Screen Actor's Guild (which is notoriously tough). One of the most popular stunts is one of the most dangerous as well: getting set on fire. To do this, the stunt person must wear several layers of protective clothing (gloves included), a hood with an oxygen tank, and must be doused in two types of gel that contain the fire and prevent the flames from burning your skin.
How Does Lighting A Match Work?
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There's a lot going on when you strike a match. A match head is made of a number of ingredients, including potassium chlorate, sulfur and powdered glass. The striking surface is made up of sand, powdered glass and red phosphorus. When the match head is dragged along the striking surface, the sand and powdered glass cause friction and heat, which is enough to convert some of the red phosphorous to white phosphorus-a chemical so volatile that it ignites in the air. The heat also breaks down the potassium chlorate in the match head, thereby releasing oxygen that serves as fuel for the fire. The oxygen combines with sulfur and keeps the flame burning. As for the gelatin, it acts as glue to hold everything together in the match head, and also provides extra fuel.
from APS Physics
Key Facts to Know
When you strike a match, chemicals produce hot gases that jet out of the match head. 0:13
Schlieren imaging captures changes in fluid density. 0:35
Watch how human breath creates a turbulent structure as it blows out a match: 1:19
Salem "Witches" Weren't Burned At The Stake
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The story of the Salem witch trials of 1692-3 is often synonymous with the burning of accused witches at the stake. During the trials, it is estimated that 200 people were accused of practicing witchcraft, and 20 were executed. Hanging was the preferred method of execution, although one man accused of witchcraft was pressed to death by heavy stones. Eventually, the colony admitted the trials were a mistake and compensated the families of those convicted.
from Today I Found Out
Key Facts to Know
Burning people alive was forbade by English law at the time of the Salem witch trials, so no "witches" actually burned at the stake. 0:10
About 200 people were accused of witchcraft during the Salem witch trials, but only 20 were executed. 3:00
Authorities commonly burned the remains of "witches" during the Salem witch trials after they died. 4:16
Can Fire Burn in Space?
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Could fire exist in zero gravity? Yes, but it would burn a lot differently than it does on Earth. A candle flame would burn equally in all directions in space.