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.


The Most Popular Viral Video in Each State


Viral videos have been around long enough for some to be considered classics. For the map below, the internet service provider GetCenturyLink rounded up the most iconic YouTube videos from the platform's 13-year history and broke them down by state.

After making a list of the most popular viral videos from the classic YouTube era through today, analysts looked at Google Trends’s YouTube search data to see which videos were being watched the most in which parts of the country. The "Wedding Entrance Dance" video is the viral content with the most widespread appeal, dominating searches in 11 states. "Charlie Bit My Finger", the video on the map with the most overall views at 860 million, topped the list of favorite bits in Illinois, Indiana, Iowa, North Carolina, and Texas. Meanwhile "Potter Puppet Pals" is the most beloved viral video in Utah, the state with highest percentage of Harry Potter fans based on how many residents like the Harry Potter Facebook page.

Many of the videos on this map were uploaded prior to 2010, but that doesn't mean the viral video is a fading art form. The YouTube landscape just looks slightly different than it did a decade ago, with ASMR and unboxing videos often topping the trending lists.

Before embarking on a nostalgia-field YouTube binge, check out the map below to find your state's favorite video.

Map of viral videos.

Key for map of viral videos.

What's the Difference Between a Break and a Fracture?

A lot of people tend to think that breaking a bone is worse than fracturing it—or perhaps they believe it's the other way around. Others may think of a fracture as a specific kind of break called a hairline crack. However, as Arkansas-based orthopedic surgeon Dr. C. Noel Henley points out in the YouTube video below, these are all common misconceptions. A fracture and a break are actually one and the same.

“There’s no difference between these two things,” he says. “A fracture means the cracking or breaking of a hard object. One is not worse than the other when it comes to breaking bones.”

Some of the confusion might stem from the fact that the word fracture is often used to describe specific kinds of breaks, as in compound fractures, oblique fractures, and comminuted fractures. In all cases, though, both break and fracture refer to any instance where “the normal structure of the bone has been disrupted and damaged,”  Henley notes.

This isn’t the only common misconception when it comes to cracked bones. The idea that a “clean break” is a good thing when compared to the alternative is a myth. Using the scaphoid bone in the wrist as an example, Dr. Henley says a clean break in the “wrong” bone can still be very, very bad. In some cases, surgery might be necessary.

According to the BBC, other bone myths include the belief that you’ll be unable to move a certain body part if your bone is broken, or that you’ll instantly know if you have a fracture because it will hurt. This isn’t always the case, and some people remain mobile—and oblivious to their injury—for some time after it occurs. Even if you think you have a minor sprain or something seemingly small like a broken toe, it’s still a good idea to see a doctor. It could be more serious than you realize.

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