Secret of Snapping Spaghetti in SLOW MOTION - Smarter Every Day 127

(Destin) Looks good to me. Nice. Hey, it's me, Destin. Welcome back to Smarter Every Day. So, I'm gonna show you something today that's fascinating. If you take a normal piece of dry spaghetti, you can do this in your home, and you bend it right up until the point it breaks. It doesn't do what you think it should. It doesn't break into two pieces, it breaks into three. It happens almost every time. You see that? That broke out of the middle.

Today on Smarter Every Day, we're gonna wait till the kids finish their dinner, and then we're gonna break out the Phantom V1610 and record this at a quarter million frames per second. And we're gonna unravel the secret of why spaghetti shatters the way it does. You're getting Smarter Every Day.

If you haven't already, run to the kitchen; do that now. Grab some spaghetti and goggle up, 'cause science is about to happen. One at a time, grab a noodle on both ends and bend it until it breaks. You'll notice that the majority of the noodles break into more than two pieces. Now you might not think this is a big deal. But it's a really big deal.

You see, it's really easy to understand why bending a rod makes it break into two pieces. The bottom is in compression, and the top is in tension. When the tension on the top exceeds the maximum allowable tensile stress, it rips it in half, and you're left with only two pieces of the rod left. So why is spaghetti different? Something else is happening here.

The simple act of snapping spaghetti has stumped brilliant scientists for years, including Richard Feynman, who, as you might know, was on the theoretical physics team during the Manhattan Project and also won a Nobel Prize for Physics in 1965. Everyone accepts that Richard Feynman was a genius, so it's no surprise that his theory about why spaghetti snaps into multiple pieces makes a lot of sense.

If you tried it by now yourself, you know that when you snap it, you feel this little vibration in your fingers. He thought that this vibration, if it was significant enough, could excite the remaining spaghetti sufficiently so that it would cause a secondary fracture down the rod. To test this theory, Feynman and a friend decided to snap spaghetti underwater to dampen out this vibration. They were surprised to find out that when they snapped it underwater, it still seemed to break into multiple pieces.

So here we are. If a smart dude like Richard Feynman can't figure this out, what chance do we have? So we're gonna figure this out in my kitchen. This is what we're doing. My wife brought home all kinds of different pasta for me, at my request. I've got them taken out here, and we're running an experiment with this high-speed camera; it's a Phantom V1610. We have a lamp set up, and we're just gonna sit and break pasta and observe.

I looked all over the internet, and the fastest research imagery I could find was 4000 frames per second. So in order to further science, we're gonna start out at at least 18,000 frames per second, which surely should tell us something, right? [slowed snap] Woah. That was fast. OK, I couldn't even tell which fracture happened first. We'll zoom it back in and go frame by frame. [snap] Yeah, it's way too fast. Both fractures happen at what seems to be the same time.

Let's look at another piece that breaks up even more and see if it sheds some light into what's going on here. [snap] What?! It's like all the fracture points are happening at the exact same time, which is crazy because we're well below a millisecond time scale here. I'm not really sure what the researchers were seeing at 4000 frames per second, but I'm not seeing it.

So let's bump this thing up to 40,000 frames per second, which is ten times faster than any research paper I've read. [snap] Hmm. OK, so we're starting to learn something. I can at least tell that the right side broke first. But both still seemed to be happening within 100 microseconds of each other, which is really, really fast.

Also, let's start to watch the rotation direction of the broken pieces. Let's watch another one and see if vibration has anything to do with that second fracture. [snap] No. In fact, it appears that the longer rods aren't even vibrating on the same time scale. Here's something though. If you look, the smaller broken pieces, when they start to rotate, always seem to rotate away from the first fracture.

The back, however, appears to be breaking downwards. It's almost as if the spaghetti is trying to straighten itself out, but it can't overcome its own mass. Buckle your seatbelt, 'cause we're going to a quarter million frames per second. [snap] Man, we had to go way faster than I thought we would to get this answer, but there it is.

I mean, it's not vibration. It's the curvature of the spaghetti as it straightens out. Think about it this way: the entire spaghetti rod is under torque, right? Because of this torque, it bends in a curve. And when a break occurs, the side near the break is now free from torque. But there's still this counter-torque built up in the rod.

So it starts to straighten itself out from left to right, rotating up and straightening out along the way. Because the spaghetti on the left is already straightened out, and the spaghetti on the right is still curved, the point where they meet is now even more curved, which causes the spaghetti to bend beyond the minimum failure radius. This results in a fracture.

It's like one side doesn't get the message fast enough. If the whole rod were to release at one time, it'd be fine, but it doesn't. It breaks itself apart along the way. Every time you have a new break, the process starts all over again. This physical phenomenon is called a cascading fracture.

Until recently, the math behind this phenomenon wasn't very well understood. But I did find a really cool French research paper on the topic, as well as a neat simulation created by some Norwegian petroleum engineers. To my knowledge, though, the video that we just watched gives more insight into this physical phenomenon than anything else that's ever been done.

We just did it at a quarter of a million frames per second, which is amazing. So there you go. The secret of snapping spaghetti is not just a party trick. The next time you boil spaghetti, be careful, because you are about to explore the very edge of scientific knowledge.

So thank you very much for watching this episode of Smarter Every Day. If you would like to get a book that talks about all the things that Richard Feynman studied, I recommend an Audible book called Surely You're Joking, Mr. Feynman. I'm listening to it right now, and it's really good. If you would like to support Smarter Every Day, go to Audible.com/smarter and download Surely You're Joking, Mr. Feynman, and you would support Smarter Every Day, and I would greatly appreciate that.

So thank you very much. I'm Destin, you're getting Smarter Every Day, have a good one.

(kid) Woo!

(Destin) You ever heard of Richard Feynman?

(Kids) No. No idea. - No idea? - I have no idea who he is, but it sounds fine. - [laughs] Well he is. He's a little different than daddy, but he's a pretty smart awesome dude.

Three. At least four. I hope this video earned your subscription. If not, just enjoy this confused fish. Thanks.