Watch Richard Feynman Explain Fire

United States Army // Public Domain
United States Army // Public Domain

Physicist Richard Feynman was a master explainer. His physics lectures are a model of clarity. His specialty is explaining one concept in the context of another concept the listener already understands.

In the video below, Feynman tackles the seemingly simple question: What is fire? This is a hard question for many of us to answer without referencing fire itself. Fire is burning. Fire is what happens when you light a match. Fire is a reaction. But aside from our existing knowledge of its effects (like flame), what is it and how does it happen? What else is fire like that we understand already?

In 1983, Feynman answered this question (among others) for the BBC on its Fun to Imagine series. He starts like so:

The atoms like each other to different degrees. Oxygen, for instance in the air, would like to be next to carbon, and if they're getting near each other, they snap together. If they're not too close though, they repel and they go apart, so they don't know that they could snap together.

It's just as if you have a ball that was [rolling and] trying to climb a hill and there was a hole it could go into. Like a volcano hole, a deep one. It's rolling along, and it doesn't go down in the deep [volcano] hole, because it starts to climb the hill and it rolls away again. But if you make it go fast enough, it'll fall into the hole.

So if you set something like wood in oxygen...there's carbon in the wood from a tree. And the oxygen comes and hits the carbon, but not hard enough. It just goes away again. The air is always [moving but] nothing's happening. If you can get it fast enough, by heating it up somehow...a few of [the atoms] come past, a few of them go over the top, so to speak.

So there you have it. If you understand what a volcano looks like and how a ball rolls under normal earth gravity, you have the start of this mental image for how fire works. Feynman's explanation manages to convey chemical behaviors in terms humans intuitively understand—the way a ball rolls—because that's the world we live in. Watch this for a delightful explanation:

The BBC has more clips (in better quality) at this slightly vintage website. You can also download the entire hour-long lecture from the Internet Archive.

[h/t: Kottke.org.]

Watch 32,000 Dominos Fall in an Extremely Satisfying Way

iStock/Khongtham
iStock/Khongtham

Lily Hevesh, known as Hevesh5 on YouTube, has achieved viral fame many times over with her ambitious domino videos. She's shown us dominos falling up a flight of stairs, dominoes toppling in a three-part spiral, and dominos collapsing in a continuous chain of record-breaking length. To make the video below, she collaborated with six fellow domino artists and set up an elaborate, freestyle design that leads to a domino fall that's incredibly satisfying to watch.

According to the video's description, this was the biggest project Hevesh and her collaborators built during a domino event she hosted earlier in 2019. The artists—which in addition to Hevesh5, included YouTube creators NC Domino, StickTrickDominoDude, Chris Wright, Jaytar42, jackofallspades98, and SmileyPeaceFun—gave themselves three-and-a-half days to set up 32,000 dominos using the most oddly satisfying domino tricks they knew.

Hevesh writes in the video description: "Everything in this setup (besides one field) was freestyled so we did not draw out a detailed floor plan. All we had was a list of satisfying domino project ideas that we built and connected on the spot."

In less than four minutes, the video showcases pyramids, spirals, and artistic patterns, all made from toppling plastic bricks. Whether or not you can name all the domino tricks that are featured, seeing them in action is mesmerizing. You can watch the full video below, and then subscribe to Hevesh5 for more domino creations.

Watch What Happens When Mannequins Misuse Fireworks

martaland/iStock via Getty Images
martaland/iStock via Getty Images

With the Fourth of July comes all the requisite warnings about fireworks safety. These sometimes-legal (check your local laws) explosives can provide a rapturous end to holiday festivities and events. They can also end in emergency room bills and tragedy.

This week, the U.S. Consumer Product Safety Commission (CPSC) set up a demonstration to illustrate how quickly the mishandling of fireworks can go wrong, and it looks like something out of the opening sequence in Saving Private Ryan:

These mannequins violate a number of safe practices for fireworks, including pointing them directly at the heads of friends and peering into the mouth of a mortar tube. There’s also a caution about trying to make fireworks at home, which can have roof-blasting consequences.

While the dummies in the video exhibit poor judgment, their sacrifice might help humans avoid a similar fate. According to the CPSC, 280 people end up in the emergency room per day in the month around July 4 as a result of fireworks-related mishaps. Hands and fingers make up most of the injuries (28 percent), with legs (24 percent) and eyes (19 percent) also being vulnerable. Nearly half (44 percent) of injuries are burns. All told, 12,900 people were treated for fireworks wounds in 2017 [PDF].

To avoid injury, it’s best to avoid fireworks that come wrapped in brown paper, since those are typically made for professional use only. It’s also a good idea to keep children away from sparklers, which can burn in excess of 2000 degrees Fahrenheit. (If you would not hand your child a blowtorch, it’s probably not a good idea to hand them a sparkler.) If you must light a firework, do it and then get as far away from it as possible.

The CPSC has capped consumer fireworks so that they contain no more than 50 milligrams of powder. More formidable explosives, like cherry bombs and M-80s, have been banned by the federal government. Most states allow at least some fireworks to be sold and used.

If the mannequins really wanted protection from accidents, they should have moved to Massachusetts; it’s the only state where all consumer fireworks are banned.

[h/t CBS Denver]

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