StarTalk Radio - Things You Thought You Knew – Oatmeal Sun

Episode Date: August 26, 2025

Why don’t rockets fly straight up? What’s really happening when you make toast? Neil deGrasse Tyson and comic co-host Chuck Nice break down the science of making toast, boiling water, and the Brachristochrone problem. NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free here: https://startalkmedia.com/show/things-you-thought-you-knew-oatmeal-sun/Thanks to our Patrons Mikey2Hearted, Katherine, Kate Donahue, rashi lutfi, Lennon Conson, Menno Baks, Lerby Exantus, Denver Finlaw, Salvador Bello, Mikimajkylu, Rebekah Miller, Anthony D'Amico, Micheal Nelson, Gene Strohl, Miloš Jovanović, Rashid Elliott, Hunter Jackson, Kristina Werden, Joe Monsanto, WideEyedWanderer, Henry Bein, T.MITTEN, zandro, David Abramowitz, Marco Baiocchi, Jordan Eames, Kecarson Singeo, Brandon Mullins, Ignacio Espinza, Jennifer, Marius Kristiansen, Ryan Plummer, Too Many Comics, David Geron, Francis Ganigan, RAYMOND MARTIN, Micheal Bartmess, Neo Pesonen, Cry 'Drew' Andrews, Average Joe, Micheal walker, Miguel, Karen Louise Roberts, Lopez125, Letitia Davis, Arvin Baccay, SNTV FAM, Joseph Zito, CaliNupe99, Stephen Roberts for supporting us this week. Subscribe to SiriusXM Podcasts+ to listen to new episodes of StarTalk Radio ad-free and a whole week early.Start a free trial now on Apple Podcasts or by visiting siriusxm.com/podcastsplus.

Hey, StarTalkians, we put together another things you thought you knew. This one mysteriously combines toast, boiling water, and launching rockets. Check it out. Welcome to StarTalk. Your place in the universe where science and pop culture collide. StarTalk begins right now. Chuck, I got another explainer for you. All right.

This has to do with making toast. Okay. I'm just saying. You know, sometimes when you bring these up, man, I feel like you just, like you're punking me. You know what I'm like, let me just see if I, what I can get Chuck to go along with. The astrophysics of making toast. You know, it's like, you know, it's like Neil deGrasse Tyson, right? World renowned scientists and science communicator.

Chuck, I'd love to talk. talk to you about something scientifically relevant. Oh, Neil, please, do tell. Let's talk toast. What? All right, so here's the deal. Okay. All right.

And I don't know if you ever paid attention to what's going on inside a toaster. Okay. All right. But it's fascinating. I have smoked a lot of weed. I have been high out of my mind. I have never looked at the toaster and went, I wonder what's going on in there. All right.

Here's a thing. Okay. Here's a thing. A toast, if you're going to toast fresh bread. Okay. Okay. It will spend most of its time in the toaster, most of the time, not browning. Okay.

And is this fresh white bread? Because that would make sense. Yes, it's easier to see the browning on white bread. So this is a white bread. example, okay? But can you blame it because, let's be honest, in bread society, you know, white bread has it the best. They got the bad.

Why would I want to give her? But the seven grain blended model is coming along. Okay. So here's the thing. And let me tell you something. Pumpernickel, there goes some property values in the bread box. I forgot all about pumpernickel. That's some dark ass bread right there.

Hey, right now. Okay. Go ahead. Never mind. I'm about to get us in trouble. I'm going to stop. All right. So if you observe the bread, most of the time, 90% of the time, I didn't know exactly,

but it's very high percent of the time it's in the toaster, it doesn't change color at all. Oh, my God. Okay. Because it can't change color as long as it's moist. Okay. Because the highest temperature you can hear. heat the bread is 212 degrees, and that's not hot enough to toast the bread. I gotcha.

I mean, that really does make sense. Think about this, right? It's like trying to start a fire with green kindling. You can't. You can't. In fact, if you put a green log on an already established fire, the log is not going to ignite. You know what's going to happen? It's going to hiss out all the moisture for the next hour, right?

Because the log can't get hotter than the highest. that water can get. And the water that's in the log tops out at 212 degrees. So you can have a 212 degree log until there's no water left. That's cool. And then it'll ignite.

That's right. Oh, wow. Okay. So your toast in the toaster, if you keep looking at it, it's going to be your white toast. It's going to be white and white and white. And what the heat is doing,

it's like, get out of there, you water molecules. Get out, get out. And it's only doing it to the top edge, not to the middle because the heat is only hitting the top edge, the outer edges, right? So, so. So the heat is like the black toast matters movement.

Yeah. Chuck, you told you need race counseling, okay? I think you can. All right. So go ahead. All right. So once all of the moisture on that outer edge of the bread has evaporated, right?

It can now toast the bread. By breaking apart the, the bread molecules, the proteins, and the carbohydrates, revealing the carbon. The carbon is black, okay? If you leave the bread in too long, it's completely black. All right, but you have all this golden tip. That all happens in like the last minute that your toast is in there. Because it took all the rest of that time to heat up the water and evaporate it.

That is pretty doggone cool, to be honest. And I got a little excited when you said that. because I've never considered it. However, I don't have a toaster. I have a toaster oven. Okay, so in the oven, any oven, if you're going to use a broiler, the same thing. Same thing. You layer the bread and you check in it and you keep checking it and you say,

it's not making progress. Let me go away for five minutes. No, because the moment the moisture is gone, that's sucker browns in instance. Absolutely. So it's not a linear, it's not a linear phenomenon. No, it's kind of like if it were a graph, it would bump along the bottom. Correct. And then all of a sudden it shoots straight up almost.

Yeah, almost straight up. Almost straight up. So, and I know this because just the other day when you, it's so weird now, I can't believe that I'm recalling this. I said, what's taking this toes so damn low? You didn't say that? Okay. And then I turned, I went into the refrigerator, I pulled out some butter and, um, fig spread. And I went back and the toast was brown.

There it is. So that is so wild. You lived this experience. I lived this experience. It's also why you can boil water in a paper cup. Okay. Okay, and I've done this experiment many times. So, wait, yeah, I mean, yeah, you just drop the paper cup inside the pot of boiling water, okay?

No, no, no, that's not what it. No, so you can take a paper cup, and you have to be careful about this because some paper cups have rims on the bottom that are not actively touching the water on the inside. That will burn, okay? But if you have a wide enough bottom and you have like a Bunsen burner, remember these, and you put the flame on the paper cup in the bottom, if the paper cup has water in it, what is the hottest temperature the paper can get? The temperature of the water.

Okay, and so it'll sit there and boil the water. And it'll keep boiling the water until all the water evaporates, then your paper cup burns. This is why it's so hard to burn someone at the steak. You think, oh, let me just ignite you.

This is very medieval here. Let's put you on the steak and just ignite you. You can't just ignite, okay? Yeah, well, there's liquid in you. Right, the real, real reason why this is very difficult to do is because we have laws against that now. That's why. Okay. That's the actual reason. It's difficult. Thank you. Let me get out of my medieval. So what they would do, especially the Catholic Church, to make sure you would burn, that sometimes they would burn you upside down and that way will control the blood or the blood would drain.

And as the blood drains, then you have no liquid left in you and you burn things. Or you can burn in other directions where you retain the blood because if you don't want the blood come out, there's some other religious ritual where the whole person has to be burned, including their blood. But then the blood has to still evaporate before anything. You'll die before all that happens, of course. But in terms of igniting the body, it just doesn't simply happen that way. And this is sped up if you have fast moving air, hot air across the food. Yes.

This is like a wind heat factor. Mm-hmm. We have an explainer on wind chill factor and wind heat factors. Yes. Okay? Because if it's cold and the wind is blowing, you feel colder. Colder. If it's hot and the air that's blowing is hotter than your skin temperature, you'll feel hotter.

Right. Okay. So if you put food in, let's say, an air fryer. Yes. What does that mean? Okay. So they are going to brown your food. fast because they're moving hot air across

and they're evaporating any possible moisture on that surface. And the faster the wind goes, the faster you'll evaporate it, and the faster you can get to the browning. Can't live without an air fryer. I'm sorry. It's amazing. They're wonderful.

Yeah, they're really air toasters. Yes. Because, you know, unless the surface is sprinkled with oil, and then the oil will fry the, you know, you can heat the oil. So you're still oil-frying, but you're using air to heat the oil to fry the food. Right. But if it didn't have any oil, it's just a fast toaster.

Exactly. You mean I spent $400 on a toaster? Yes, you did. Yes, you did. You did indeed. So that's everything you wanted to know about toast and why it's not a linear process. Well, that was fun. Oh, don't you do?

Ooh, ooh, ooh, do this experiment. Okay. Take a slice of bread. Leave it out until it just gets hard. A little crusty. Just leave it out. Okay? We'll just get hard.

It's no longer squishy. And then you have another one that's squishy that you just took out of the bag. Okay. They're both at the same temperature. Right. Okay. Now put them both in your, in your toaster oven. We're both in the toaster.

and the one that had the lost moisture will toast 10 times faster. Okay. Oh, yeah. Oh, there you go. So, yeah, and it's already on its way to being toast. That's right. You leave it out. Well, why do you keep leaving a bread out?

I'm toasting a bread, man. Pre-toasting. Pre-toaster. It's a pre-toast. And one other thing, a reminder of how surface deep the color is. Okay. Because it's only what that. sort of radio of energy can touch.

And anything's behind anything else. It's not seeing your toaster thing, all right? So a reminder of that is, if you happen to burn the toast, you just take a bread knife or a knife, you know, a knife and scrape off the black. Right. And then there's like, listen, and you can salvage many of burnt toast that way.

Or you could just accept the fact that it is black and enjoy it for its beautiful blackness. You could do that as, Well, okay. Yeah, Chuck totally, definitely needs race therapy. We're going to work on this. I know. I can't help it.

So, so maybe that's more than you ever care to know about making toast. But I just thought I put that. The thermodynamics of toasting. That is awesome. We got a title is just that. The thermal dynamics of toasting. Okay. And so, and the, and the takeaway here is how.

However long you're staring at the unbrowned toast, let that not be the measure of how much longer you have to wait. Yes. I'm Brian Futterman, and I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson. So, Chuck, I'm going to tell you how to boil water. So for this explainer, I am going to go and get a sandwich. You fill a pot with water. Now you put it on the stove, then you turn on the heat, be it electric, coil, or gas.

This is groundbreaking stuff. So you're heating the pan. Right. And then the bottom of the pot is heating the bottom of the water. That makes sense so far. So you'd expect the water at the bottom of the pot to be hotter than the water at the top of the pot. Yeah. So as it gets hot, the water molecules vibrate faster and faster.

Right. If you're a molecule sitting next to me and you're not vibrating as fast as I am. I'm like, calm down, man. What is your problem? But you will ultimately succumb and my vibrations will send you into vibrating. You will send the adjacent molecules next to you. It's called conduction.

It's how, if you have a fireplace poker or the handle of an iron pan on the stove, the pan gets hot, eventually the handle gets caught. Lord, have I learned that the hard way. Okay. So the iron molecules start vibrating, and they tickle the molecules next to it, set them vibrating, and that is heat energy going out of the pan, up the handle to your hand to burn you, unless you get a pot holder. Right.

So the liquid will conduct heat until that's not fast enough. Conducting is slow. You can hold the handle of an iron pan for at least five minutes. A long time. Meanwhile, you're frying an egg, right? Yeah, exactly. So there's a point where the heat is vibrating the molecules faster than the molecules can communicate that fact to molecules above it.

Uh-huh. So the solution to this is blobs of water rise up from the bottom. You don't see the early bits of this, okay? Because the water is completely transparent and there aren't any bubbles yet. Right. But the hot water rises. Right. Physically moves.

That can't happen in your iron pan because it's solid. The iron can only move heat through conduction. Right. But the moment the heat becomes significant, whole pockets of water will rise up, replaced with cool pockets of water that were above that come in below. If I rise up, something's got to take its place. Right. If you want to test this next time, put in a few raisins at the bottom.

Sounds like an awful dish. So you'll see the raisin bob up and down inside the liquid. And it's doing that because it's following the pockets of water. There you go. So convection is a way to get heat from one place to the other by physically moving blobs of the stuff. And so convection can't happen in solids, but it can happen in liquids and in air. Air, gas, okay. But it's not boiling yet.

What happens when it boils? I'll tell you when it's boiling. It's boiling when at the bottom of the stove, it is so hot. The water at the base of the pot turns into steam. Wait, inside. Inside. Wow. So you have a ball of steam there, and plus it's gas.

Gas underwater is going to rise fast. Exactly. Now, the early bubbles of steam, these are cool. The early bubbles, you'll see them start, and as they move their way up, they get smaller and smaller and they disappear. Right. Because the water above that layer is not at boiling. temperature yet. It's cool. It's cooler. So it's cooling down this steam bubble, turning it back into water. Interesting. So when the bubble is formed and keeps the same size, the entire route to the

top, then you have 212 degrees boiling water. So boiling water is really just, it's just water They're farting, basically. That's exactly what I was thinking, Chuck. If you fart in a swimming pool, that bubble will not disappear. That'll just stay a bubble all the way up. That's the easiest way to get kicked out of a group party. Why are there bubbles coming from your suit? Coming from your rear end.

No, none of what I just said is why I have this explainer with you. Okay, plot twist. Have you ever? had a pure pot of water boil over. Oh, no, it never boils over. But wait, when you make spaghetti, it can boil over. Yes, it can. What is it the most boil over substance known to man in a morning stove?

The most, oh, oatmeal. Oatmeal. Oatmeal. Oatmeal. So why does water not boil over, but oatmeal does? Why? I will tell you. I'm ready. There they are, slowly coming up to temperature.

The pure water gets to 212, a blob of steam rises up and escapes the top. Right. What happens to that same blob of steam in the oatmeal? It can't get out. Right. There's oatmeal in the way. But it has to get out. Thermodynamically, it has to escape.

So you have these bubbles and they say, we're getting out no matter what. We're busting loose out of this pot. And the only way to do that is to expand the layers of oatmeal so that it has pockets of water that it can come out through. If you start out with a pot of oatmeal, that's one third full, that puppy will expand to the complete height of the pan so that the steam can get out. The sun, when it dies, you always heard it say, it becomes. a red giant. Right. When the sun dies, it runs out of hydrogen in its core. It converted all the hydrogen to helium. There's a certain luminosity associated with that. Fine. Now I just have

helium. What's next? The sun collapses, then it starts fusing helium into carbon. That happens at a higher luminosity. The sun gets brighter. More energy is coming in from the core of the sun. But wait, that energy can't get out of the previous sun. It has the same problem with the oatmeal. Okay? The previous sun had a transparency of energy to it that gave it its current size. Right. When you boost the energy level of the core, it can't get out until it busts out.

And it is going to get out. And on route, it takes the sun and swells it into the size. of a red giant star. Now the energy can get out. And it goes from its current size to hundreds of times bigger. Oh my goodness. You thought your oatmeal spilled over. The sun is basically spilling over out of its pot. Wow. Which is why if you want to tame the oatmeal, you have to lower the heat. Lower the heat as much as you can. We can't do that to the sun. The sun is stuck with the high energy. It's going to puff up and become a huge red giant star. So under high heat, the Oatmeal wants to become a big giant star, basically, trying to get the energy out.

Right, right. Lower the heat, which the sun doesn't have the power to do. Now it can bubble and you can cook the oatmeal. So the sun has no choice, but to go ahead to keep expanding. Correct. Until it becomes its own delicious breakfast explosion. Whereas you, the chef in the morning, have the option to lower the heat on the oatmeal. Right.

So the oatmeal boils over for the same reason the sun gets big. The energy can't get out, and it has to thin things up above it so that the energy can find its way out. And it does. That's super cool. Jack, I get some obscure stuff to share with you. My favorite, obscure. I don't know if it'll be worth it, but let me test it out on you. What distinguishes a rocket from an airplane, among many things, is that a rocket has to work as it ascends the atmosphere where there's less and less oxygen.

Okay. So it can't depend on oxygen in the air for the combustion in the rocket. Whereas an airplane, it doesn't have to carry its oxygen. because the oxygen is sitting there mining its own business in the atmosphere. And then the airplane sucks it in and... Sucks it in and mix it with the fuel and ignites it. And there you have it. So the way they say that in rocket lingo is the rocket carries its own oxidizer.

Oh, okay. The space shuttle, which doesn't launch anymore, had two different kinds of fuel. You've heard of the solid rocket boosters on the side. We still use those today. You know how they burn? They burn from the middle outward. as though you're unraveling a toilet paper roll from the center. Interesting.

So if you have a toilet paper roll, remove the cardboard, and then you just start pulling on it. Right. It slowly unravels from the center. So in a solid rocket booster, it's a cylindrical core of fuel, and as it burns, it only has one exit hole, and that's the bottom.

Right. And that exit hole gets wider and wider and wider, as it continues to burn. It ablates that inner surface until it runs out completely and then you're done and then you drop them off and you keep going.

Interesting. Yeah, so that's how the solid rocket boosters work. By the way, once they're ignited, you can't shut them off. I hope you're igniting them at the right time.

And they're clamped down until they ignite. And then when they ignite, they break away because you can't, there's no stop in them. Once they're lit, the shuttle's off.

Okay? It's like, there it is. You can't do anything until they're done. Whereas the main engine, you can throttle that. You can go high or low. The main engine was that big orange segment. And that has two tanks in it, hydrogen and oxygen. The hydrogen tank is twice as big as the oxygen tank. I think I'm hearing a little H2 and 1.H2. Oh, H2. Oh. How do you concentrate the most amount of this hydrogen gas and oxygen gas? You liquefy it. So you chill it so that it liquefies, and then you have a rather extensive set of valves and nozzles that recombine the hydrogen and the oxygen, and that is highly exothermic, which means it releases energy, and what is the waste product? Well, it's got to be water. Water, there it is. So that begs the question, why isn't all of our fuel done this way? I mean, the planet is dying. We actually have this technology? Some car, they call hydrogen fuel cells.

Okay, that's right. Hydrogen is very flammable. So I don't know if they've worked out the engineering mechanics of how to make that practical. How to put that together without blowing everybody up. Right. Exactly. A little like, oh, the humanity every other day.

Stop. Stop. Stop. Did you know that when Orson Wells did the radio play of H.G. Wells's War of the World. Right. He studied the vocal intonations of that announcer. You're kidding. me. And copied them for the announcer who saw the aliens, making everything sound that much more

dramatic and tragic. And tragic and real and scary. Do you ever notice when it launches, a few seconds later, it executes the what? The roll. The role program. What I'm about to describe is you for everything that goes in orbit. Half the energy of that rocket is not there to get it up into space. Half. Half the energy is to take it down range. Uh-huh.

That's why every rocket you have ever seen launched doesn't just keep going up. Ever stop and wonder? When I was younger and I would watch these launches because they were such a big thing and you had to watch them

even in school. I used to think, well, they're never going to make it to space. They're going sideways. Thank you. That's an observant point. to make. So it goes from zero miles per hour to 18,000 miles per hour sideways. Nice. Because once the rockets stop, does it fall out of the sky now? No. Wait, it achieves orbit. So what is orbit? There's

that one magic speed where you are going so fast down range that you are falling to Earth at the same rate that Earth is curving away from you. And Isaac Newton first demonstrated that, and that is the definition of an orbit. You don't need rockets. You will stay in that configuration. So my only point is so many people look at rocket launchers and think they're going up into space.

Right. When what we call space in the zero-g environment, when people go, is orbit. Right. You go into orbit around Earth. they're not very high above Earth's surface, a couple hundred miles. That's it. That's the distance from New York to Boston. Yeah. New York to Washington, D.C. You could drive that distance in four hours. Yep. Obeying speed limits. It's just something that people might not have noticed. Now,

if you're not going into orbit, then all of your energy is going to just go up and then you just drop back to Earth. The Bezos Branson billionaire boys race. Bezos Branson's billionaire's boys race That's amazing I love it All right Elon went into orbit Right

My man Elon knows what orbit is He knew that he had to get out of here He knew He needs an escape hatch He was like Coming after me I'm planning for the future I'm gonna find the way to get out of here

I'm planning for the future When the pitchforks are coming Bezos and Branson They can come back. They got a place to come back to. I know. I got to go. So they, Bezos and Branson, what they're doing is they're going up and then shutting off their engines and just falling back to Earth. Right. They land in the same place they took off from. All right. So they didn't go downrange at all. They did not go into orbit.

So they go up and then they fall. And while you are falling where there's no air molecules, which is that famous Carmen line that they reach, you drop you from there, you are weightless. I'll tell you one last thing, which is completely obscure, is for physics geeks out there. Okay. There's something called the brachrystochrome problem. Okay. Now, you certainly are going deep.

Now, this is a deep cut on the B side. Let's have a round ball at some height. And it wants to get to the bottom of a hill. The question is, what shape should that hill take so that the ball gets to the bottom of the hill fastest? If you make the hill just a straight line from where it is to the bottom, okay, it'll roll down and it'll get there. Yes. But if you make the hill drop first and then curve out the bottom, you can get some serious speed here, and that stuff, that puppy will roll out fast, okay? This is called the brachrystochrome problem.

And it required sort of Hamiltonian representations of the energy of the system to solve it. Okay? The Brunuli brothers pose these to each other's. They were two math brainiacs. Anyhow, the solution to this problem is first a drop, a pretty steep drop, before it curls out to the bottom. And that will beat the straight line every time. Of course. That curve, if you flip it up,

That is the trajectory to launch a rocket. Oh. Oh, watch out. Yo, that is a physics mic drop right there. Oh. Yeah. So that's how to get into orbit the most efficiently. It's very elegant, by the way.

Yeah, and it's just an interesting question. When you're curious and you're mathematically literate and you know a little bit of physics, these questions come up in your life and you're compelled to solve them. as the Bernoulli brothers did. Nice. Oh, those Bernoulli brothers, you know, they were something at a cocktail party,

that's for sure. That's for sure. That's really super cool. All right. That's been another StarTalk Explaner. with my co-host, friend and buddy, Chuck Nice. Always a pleasure. Neil deGrasse Tyson here, as always, keep looking up.