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.]

19 Common Things Science Hasn’t Figured Out

YouTube
YouTube

Whether we want to admit it or not, everyone cries. And while experience has taught us that it's a seemingly natural reaction to being either incredibly sad or incredibly happy, scientists have yet to figure out exactly why that salty discharge pours from our eye sockets when we're feeling emotional. It could be a way to bond with our fellow humans, or a way to alert someone else that something is amiss. But these are all just guesses, as weeping is just one of many everyday behaviors the world's smartest brains still haven't quite cracked the code on yet.

Join editor-in-chief Erin McCarthy as she digs into the science—or lack thereof—of 19 seemingly normal things we do that are a mystery to scientists (you can add sleeping, laughing, and hiccuping to that list, too) with the first edition of our all-new Mental Floss List Show. There's a fancy new set, a fancy new host, and plenty of mind-boggling topics we'll be discussing. So put on your smartypants and check out the full episode below.

For more episodes like this one, be sure to subscribe here!

A Clue on the Ceiling of Grand Central Terminal Shows How Dirty It Was 30 Years Ago

iStock.com/undercrimson
iStock.com/undercrimson

The mural above the concourse at Grand Central Terminal is one of the most gawked-at ceilings in New York City, but even daily commuters may have missed a peculiar feature. Tucked at the edge of the green and gold constellations is a rectangular black mark. The apparent blemish didn't get there by mistake: As Gothamist explains in its new series WHY?, it was left there by restorers when the ceiling was cleaned more than 20 years ago.

Prior to the Metropolitan Transportation Authority's renovation of Grand Central in the 1990s, the concourse was a lot dirtier. The station itself was constructed in Manhattan in the early 1900s, and the celestial scene that's on the ceiling today was painted there in the 1940s. It took only a few decades for tobacco smoke and other pollutants to stain the mural so badly that it needed to be restored.

Using Simple Green-brand cleaning solution and cotton rags, conservators spent two years scrubbing nearly every inch of the ceiling back to its former glory; the one part they skipped was a 9-inch-by-18-inch patch in the northwest corner. Sometimes, when doing a major cleaning project, preservationists will leave a small sample of the art or artifact untouched. If the cleaning products did any damage to the paint, the patch gives future preservationists something to compare it to. It also acts as a snapshot of what the mural looked like in its old condition.

To hear more about the mural and its dirty secret, watch the video from Gothamist below.

[h/t Gothamist]

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