Things You Thought You Knew – Oatmeal Sun

Summary

StarTalk Radio – "Things You Thought You Knew: Oatmeal Sun"

Host: Neil deGrasse Tyson
Co-Host: Chuck Nice
Date: August 26, 2025

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Episode Overview

In this lively "Things You Thought You Knew" episode, Neil deGrasse Tyson and comedian Chuck Nice embark on a scientific journey that links seemingly unrelated household phenomena—making toast, boiling oatmeal, and launching rockets—to reveal the universal principles of thermodynamics and physics that underpin them all. As always, science collides with pop culture and humor for an illuminating and entertaining exploration.

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Key Discussion Points & Insights

1. The Physics of Toasting Bread

• Why Doesn’t Bread Brown at First?

  • Moisture Content Holds Back Browning: Bread doesn’t brown until its surface moisture evaporates. The bread “just sits there” mostly unchanged until late in the toasting process ([04:30]–[04:42]).

  • Neil Tyson: “If you observe the bread, most of the time, 90% of the time...it's in the toaster, [it] doesn't change color at all." ([04:30])

• Temperature Limit due to Water

  • Bread can't get hotter than 212°F/100°C (boiling point of water) while water is present, inhibiting browning reactions.

  • Neil Tyson: "Because it can't change color as long as it's moist. Because the highest temperature you can heat the bread is 212 degrees. And that's not hot enough to toast the bread." ([04:44])

• Analogy to Burning Green Logs

  • Just like wet logs won’t ignite until they’re dry, bread only browns once it’s lost enough water ([05:10]).

• The Sudden Browning

  • Once moisture is gone, browning (Maillard and caramelization reactions) happens quickly in about the last minute ([06:11]–[06:47]).

  • Chuck Nice: “If it were a graph, it would bump along the bottom, and then all of a sudden, it shoots straight up. Almost.” ([07:30])

Notable Moment:

• Chuck recalls real-life toaster experience:
  • “I said, what's taking this toast so damn long? ... And I went back, and the toast was brown.” ([07:36]–[08:09])

2. Boiling Water in Paper Cups & Why Oatmeal Boils Over

• Why Can You Boil Water in a Paper Cup?

  • A paper cup in a flame won’t burn if it’s filled with water, because the cup's temperature is limited by water’s boiling point until all water is gone ([08:15]–[08:25]).

  • Neil Tyson: “The hottest temperature the paper can get? The temperature of the water.” ([08:30])

• Thermodynamics of Boiling Over:

  • Pure water rarely boils over, but oatmeal is infamous for it.

  • In oatmeal, water vapor/steam can't escape easily, forcing the oatmeal to expand and spill out as steam tries to find a path–a process likened to the Sun becoming a red giant ([22:20]–[25:32]):

    • Neil Tyson: "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." ([25:21])

Timestamped Segment:

• Sun vs Oatmeal Analogy: ([23:29]–[25:32])
  • When the core of the Sun burns out its hydrogen, extra energy gets trapped until it “busts out” by expanding, just like oatmeal boiling over.

3. Heat Transfer in Cooking

• Conduction: Heat is transferred molecule by molecule (e.g., a hot pan handle) ([18:03]).
• Convection: In water, blobs of hot water rise, transferring heat more efficiently ([19:07]–[19:38]).
• Why Raisins Jump in Boiling Water: They follow convection currents ([19:51]–[20:06]).
• Boiling vs. Browning: Discussing how only when heat surpasses the evaporative barrier—when water is gone or surface dry—does browning occur.

Notable Moment:

• Boiling and "farting" analogy:
  • Chuck Nice: “Boiling water is really just... water farting, basically.” ([21:24])

4. Air Fryers & Wind Heat Factor

• Air Fryers as Air Toasters:
  • Fast-moving hot air in air fryers rapidly removes moisture, speeding up browning ([10:44]–[11:26]).
  • Neil Tyson: “They're really air toasters...if it didn't have any oil, it's just a fast toaster.” ([11:07]–[11:30])

5. Experiment Suggestions

• Pre-toasting Bread:
  • Compare toasting time between fresh and stale (dried) bread: dry bread toasts much faster ([11:51]–[12:21]).
• Rescuing Burnt Toast:
  • Scrape off the surface and the underlying bread remains edible ([13:03]).

6. Rocket Science: How Rockets Differ from Airplanes

• Rockets vs. Planes: Oxidizer

  • Rockets carry their own oxidizer, planes use atmospheric oxygen ([28:00]).

• Solid Rocket Boosters:

  • Burn outward from the center; unrecoverable once ignited ([28:56]–[29:36]).

• Space Shuttle Main Engine:

  • Uses liquid hydrogen and oxygen, produces water as a byproduct ([30:09]–[30:38]).
  • Brief discussion on possible use of hydrogen fuel for clean energy and its engineering challenges ([30:48]–[31:01]).

Notable Moment:

• Water as Rocket Byproduct:
  • Neil Tyson: “So you chill [hydrogen and oxygen] so that it liquefies. ...And what is the waste product? ...Water. There it is.” ([30:13]–[30:38])

7. Why Rockets Fly Sideways: Achieving Orbit

• Orbit is Not "Up," It's "Sideways":

  • Half the rocket's energy goes into accelerating sideways (downrange) to stay in orbit, not just escaping Earth's gravity ([31:38]–[32:03]).

  • Neil Tyson: “For everything that goes in orbit, half the energy of that rocket is not there to get it up into space, half...is to take it downrange.” ([31:38])

• Orbit Explained:

  • Once moving fast enough sideways, the rocket “falls” around the Earth, matching Earth's curvature ([32:03]–[33:07]).

• Difference Between Suborbital and Orbital Flight:

  • Bezos and Branson went suborbital—up and then down, no orbit. Elon Musk reached orbit ([33:48]–[34:24]).

8. Bonus Deep Cut: The Brachistochrone Problem

• Fastest Path Under Gravity:
  • The quickest descent path isn’t a straight line but a curve (like a roller coaster). This same logic shapes the initial trajectory of launching a rocket for optimal efficiency ([35:04]–[36:19]).
• Fun Physics History:

  • Bernoulli brothers formulated and solved this in the 18th-century.

  • Neil Tyson: “If you flip it up, that is the trajectory to launch a rocket. ...That is a physics mic drop right there.” ([36:19]–[36:29])

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Notable Quotes & Moments

• On Toasting Bread:
  • “The heat is like, 'Get out of there, water molecules! Get out, get out!'” – Neil Tyson ([05:48])
• On Cooking Oatmeal and the Sun:
  • “Oatmeal boils over for the same reason the Sun gets big: the energy can't get out.” – Neil Tyson ([25:21])
• Rocket Trajectory Mic Drop:
  • “If you flip it up, that is the trajectory to launch a rocket. ...That is a physics mic drop right there.” – Chuck Nice ([36:19])
• Humor Highlight:
  • “Boiling water is really just... water farting, basically.” – Chuck Nice ([21:24])
• On Real-life Toaster Science:
  • “I lived this experience.” – Chuck Nice ([08:13])

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Timestamps for Key Segments

• [02:25] – Beginning the toast science explainer
• [05:10] – Moisture analogy with green logs
• [06:47] – Nonlinear toasting graph analogy
• [08:25] – Boiling water in a paper cup
• [10:44] – Air fryer/air toaster discussion
• [11:51] – Bread moisture and toast experiments
• [13:03] – Salvaging burnt toast
• [17:20] – Boiling water and convection currents
• [22:20] – Why oatmeal boils over and the red giant sun analogy
• [25:21] – The energy escape principle for oatmeal and the sun
• [28:00] – Rockets vs. airplanes and rocket oxidizers
• [30:38] – Water as rocket exhaust and hydrogen fuel cell mention
• [31:38] – The true nature of orbit and sideways launches
• [33:48] – The Bezos/Branson suborbital distinction
• [35:04] – Brachistochrone problem and rocket trajectories
• [36:19] – Physics "mic drop" moment

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Tone & Style

True to StarTalk's signature style, the episode blends clear scientific explanations with pop-culture references and humor. Neil deGrasse Tyson delivers sound science with metaphors and food analogies, while Chuck Nice injects wit, playfulness, and relatable real-life observations. The mood remains accessible, curious, and frequently laugh-out-loud funny.

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Summary Takeaway

From your toaster to the sun to the launchpad, temperature, energy, and the laws of physics govern not just breakfast but the universe itself. Whether boiling oatmeal or launching rockets, understanding what’s really happening “under the hood” reveals just how connected everyday phenomena are to cosmic principles.

Final Word:
Neil deGrasse Tyson: “As always, keep looking up.” ([37:20])

Transcript

[A]

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[B]

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. Star talk begins right now. Chuck, I got another explainer for you.

[A]

All right?

[B]

This has to do with making toast.

[A]

Okay. I'm just saying, you know, sometimes when you bring these up, man, I feel like you just like you punking me, you know, like I'm like, just like. Let me. Let me just see if I what I can get Chuck to go along.

[B]

With the astrophysics of making toast.

[A]

You know, it's like you Know, it's like Neil Degrasse Tyson, right? World renowned scientist and science communicator. Chuck, I'd love to talk to you about something scientifically relevant. Oh, Neil, please, do tell. Let's talk toast.

[B]

What? All right, so toast. 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, listen. But it's fascinating.

[A]

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.

[B]

All right, here's the thing.

[A]

Okay?

[B]

Here's the thing. Toast. If you're gonna toast fresh bread, okay? Okay. It will spend most of its time in the toaster, most of the time not browning.

[A]

Okay? And is this fresh white bread? Cause that would make sense.

[B]

Yes. It's easier to see the browning on white bread. So this is a white bread example, okay?

[A]

Can't you blame it because let's be honest, in bread society, white bread has it the best.

[B]

That got the best.

[A]

Why would I wanna give em.

[B]

But the seven grain blended model is coming along, okay? So here's the thing.

[A]

And let me tell you something.

[B]

Pumpernickel.

[A]

There goes your property values in the bread box.

[B]

I forgot all about pumpernickel. That's some dark ass bread right there, right now. Okay, Go ahead. Never mind.

[A]

I'm about to get us in trouble. I'm gonna stop.

[B]

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.

[A]

Oh my God.

[B]

Okay. Because it can't change color as long as it's moist.

[A]

Okay.

[B]

Because the highest temperature you can heat the bread is 212 degrees. And that's not hot enough to toast the bread. I gotcha.

[A]

I mean, that really does make sense.

[B]

Think about this, right?

[A]

It's like trying to start a fire with green kindling.

[B]

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

[A]

That's right. Oh, wow.

[B]

Okay, so your toast in the toaster, if you keep looking at it, it is 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.

[A]

You.

[B]

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.

[A]

So the heat is like the black toast matters.

[B]

Movement.

[A]

Yeah.

[B]

Chuck, you need race counseling. Okay. I think you. All right, so.

[A]

So go ahead.

[B]

All right, so once all of the moisture on that outer edge of the bread has evaporated.

[A]

Right.

[B]

It can now toast the bread by breaking apart the bread molecules, the proteins, and the carbohydrates, revealing the carbon. The carbon is bl.

[A]

Black.

[B]

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.

[A]

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.

[B]

Okay. Okay. So in the oven, any oven, if you're gonna use a broiler, the same thing, you layer the bread and you check, and you're checking it, and you keep checking it. You say it's not making progress. Let me go away for five minutes. No, because the moment the moisture's gone, that's sucker brown's in instance.

[A]

Absolutely.

[B]

Okay, so it's not a linear. It's not a linear phenomenon. That's what I'm trying to say.

[A]

No, it's kind of like if it were a graph, it would bump along the bottom.

[B]

Correct.

[A]

And then all of a sudden, it shoots straight up. Almost.

[B]

Yeah, almost straight up.

[A]

Correct. 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 toast so damn long? You did say that.

[B]

Okay.

[A]

And then I turn, I went into the refrigerator, I pulled out some butter and fig spread, and I went back, and the toast was brown.

[B]

There it is.

[A]

So that is so wild.

[B]

You lived this experience.

[A]

I lived this experience.

[B]

It's also why you can boil water in a paper cup.

[A]

Okay.

[B]

Okay. And I've done this experiment many times, so.

[A]

So wait, you. Yeah, I mean, yeah, you just drop the paper cup inside the pot of boiling water. Okay.

[B]

No, no, no, that's. That's not what I. No. So you can, 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, you put the flame on the paper cup in the bottom. If the. 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 stake. You think, oh, let me just ignite you. This is very medieval here, let's put you on the stake and just ignite you. You can't just ignite. Okay. You have all this liquid in you.

[A]

Right. The real reason why this is very difficult to do is because we have laws against that now. That's why. Okay.

[B]

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. The blood would drain. And. And as the blood drains, then you have no liquid left in you and you burn faster. 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 any. You'll die before that happens. Of course. But in terms of igniting the body thing, it just doesn't simply happen that way. And this is sped up. If you have fast moving air, hot air across the food.

[A]

Yes.

[B]

This is like a wind heat factor. We have an explainer on wind chill factor and wind heat factors.

[A]

Yes.

[B]

Okay. Because if it's cold and the wind is blowing, you feel colder.

[A]

Colder.

[B]

If it's hot and the air that's blowing is hotter than your skin temperature, you'll feel hotter.

[A]

Right.

[B]

Okay. So if you put food in, let's say an air fryer.

[A]

Yes.

[B]

What does that mean? Okay, so they are gonna 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. The faster you can get to the browning.

[A]

Can't live without an air fryer. I'm sorry. It's amazing. They're wonderful.

[B]

Yeah, they're really air toasters 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.

[A]

Right.

[B]

But if it didn't have any oil, it's just a fast toaster.

[A]

Exactly. You mean I spent $400 on a toaster? Yes, you did. Yes, you did. You did indeed.

[B]

So that's everything you wanted to know about toast and why it's not a linear process.

[A]

Well, that was fun, what you do.

[B]

Ooh, ooh, ooh. You can do this experiment.

[A]

Okay.

[B]

Take a slice of bread, leave it out until it just gets hard, a little crusty. Just leave it out.

[A]

Okay.

[B]

Won't get crusty. It'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.

[A]

Okay.

[B]

They're both at the same temperature, right? Okay, now put them both in your toaster oven. We're both in the toaster, and the one that had the lost moisture will toast ten times faster.

[A]

Okay.

[B]

Oh, yeah.

[A]

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 the bread out? Toasting the bread.

[B]

Toasting the bread. Pre toasting it. Pre toasting. It's a pre toast. And one other thing. A reminder of how surface deep the color is. Because it's only what that sort of radiative 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, not, you know, a knife and scrape off the black.

[A]

Right?

[B]

And then there's like, listen. And you can. You can salvage many a burnt toast.

[A]

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.

[B]

Okay. Yeah, Chuck totally. Definitely needs race therapy. We're gonna work on this. I can't help. So maybe that's more than you ever care to know about making toast? But I just thought I'd put that the Thermodynamics of Toasting.

[A]

That is awesome. We gotta title this just that. The Thermodynamics of Toasting. Okay. The toast.

[B]

Yeah. And so. And the takeaway here is. However long you're staring at the unbrowned toast, let that not be the measure of how much longer you have to wait.

[A]

Yes.

[C]

This episode is brought to you by Progressive, where drivers who save by switching save nearly $750 on average. Plus auto customers qualify for an average of 7 discounts. Quote [e-mail] to see if you could save Progressive Casualty Insurance Company and affiliates national average 12 month savings of $744 by new customers surveyed who saved with Progressive between June 2022 and May 2023. Potential savings will vary. Discounts not available in all states situations this is an ad for the Active Cash credit card from Wells Fargo. That's a mouthful, but that's because it packs a lot in. Earn unlimited 2% cash rewards on purchases made with it, big or small. So whether it's buying tickets to the game with your mum or grabbing a coffee with your dog, earn unlimited 2% cash rewards on purchases made with it. Say it with the Active Cash credit card from Wells Fargo. Learn more@wells fargo.com ActiveCash terms apply. What's more stressful than a packed calendar running out of coffee right before a meeting? Now that's a real pain. Thrive Market's back to School sale is the perfect time to stock up and reset. No school schedule required. Whether it's pantry staples, snacks, vitamins or skincare, Thryv makes it easy to shop high quality essentials without the errands or ingredient labelled deep dives. Popular picks like Aloha protein bars, simple mills, crackers and poppy drinks are delivered fast with savings of up to 25%. Smart filters make it simple to shop by diet or lifestyle. And the Healthy Swaps tool helps upgrade regular buys. No labor stress included. It's so easy. All I do is lean into their tools. I organize deliveries I want to the time that suits me best. I can one off or rinse and repeat. It's so simple. Plus I can trust the ingredients are certified organic and the suppliers are ethically sound. Not only am I eating healthy and staying in shape, but my wallet feels better for shopping. Thrive and now's the best time to try Thrive Market. You'll get up to 25% off select items and new members get 30% off their first order plus a free gift. Go to thrivemarket.com startalk to start saving. The sale ends August 31st. Don't miss it.

[B]

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.

[A]

So for this explainer, I am going to go and get a sandwich.

[B]

You fill a pot with water. Now you put it on the stove, then you turn on the heat maker, be it electric coil or gas.

[A]

This is groundbreaking stuff.

[B]

So you're heating the pan.

[A]

Right.

[B]

And then the bottom of the pot is heating the bottom of the water.

[A]

That makes sense so far.

[B]

So you'd expect the water at the bottom of the pot to be hotter than the water at the top of the pot.

[A]

Yeah.

[B]

So as it gets hot, the water molecules vibrate faster and faster.

[A]

Right.

[B]

If you're a molecule sitting next to me and you're not vibrating as fast.

[A]

As I am, I'm like, calm down, man, calm down. What is the problem? Geez.

[B]

But you will ultimately succumb, and my vibrations will send you into vibrating. You will send 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.

[A]

Lord, have I learned that the hard way.

[B]

Okay, so the iron molecules start vibrating and they. 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.

[A]

Right.

[B]

So the liquid will conduct heat until. That's not fast enough. Conducting is slow. You could hold the handle of an iron pan for at least five minutes.

[A]

Long time.

[B]

Meanwhile, you're frying an egg.

[A]

Right? Yeah, exactly.

[B]

So. So there's a point where the heat is vibrating the molecules faster than the molecules can communicate that fact to molecules above it.

[A]

Aha.

[B]

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. But the hot water rises, physically moves. That can't happen in your iron pan because it's solid. The iron can only move heat through conduction.

[A]

Right.

[B]

But the moment the heat becomes significant, whole pockets of water will rise up. Replace with cool pockets of water that were above that come in below. If I rise up, something's gotta take its place.

[A]

Right.

[B]

If you want to test this next time. Put in a few raisins at the bottom.

[A]

Sounds like an awful dish.

[B]

So you'll see the raisin bob up and down inside the liquid. Ooh. And it's doing that because it's following.

[A]

It's following the pockets of water.

[B]

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 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.

[A]

Wait, inside?

[B]

Inside.

[A]

Wow.

[B]

So you have a ball of steam. There's. And plus, it's gas. Gas underwater is gonna rise fast.

[A]

Exactly.

[B]

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.

[A]

Right.

[B]

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.

[A]

Interesting.

[B]

So when the bubble is formed and keeps the same size, the entire root to the top, then you have 212 degrees boiling water.

[A]

So boiling water is really just. It's just water farting, basically.

[B]

That's exactly what I was thinking, Chuck. If you fart in a swimming pool, the that bubble will not disappear. That'll just stay a bubble all the way up.

[A]

That's the easiest way to get kicked out of a hoop party. Why are there bubbles coming from your soup?

[B]

Coming from your rear end? No, none of what I just said is why I have this explainer with you.

[A]

Okay, plot twist.

[B]

Have you ever had a pure pot of water boil over?

[A]

Oh, no, it never boils over.

[B]

But wait, when you make spaghetti, it can boil over.

[A]

Yes, it can.

[B]

What is the most boil over substance known to man in a morning stove?

[A]

The most.

[B]

Oh, oatmeal. Oatmeal.

[A]

Oatmeal.

[B]

Oatmeal. Oatmeal. So why does water not boil over, but oatmeal does?

[A]

Why?

[B]

I will tell you.

[A]

I am ready.

[B]

There they are. Slowly coming up to temperature. The pure water gets to 212. A blob of steam rises up and escapes the top.

[A]

Right.

[B]

What happens to that same blob of steam in the oatmeal? It can't get out.

[A]

Right.

[B]

There's oatmeal in the way, but it has to get out.

[A]

Right.

[B]

Thermodynamically, it has to escape. So you have these bubbles and say, we're getting out.

[A]

We're going to.

[B]

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 will. When it dies, you always heard it say it becomes a red giant.

[A]

Right.

[B]

When the sun dies, it runs out of hydrogen in its core. It converted all the hydrogen to helium. All right? 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. Had a transparency of energy to it that gave it its current size.

[A]

Right.

[B]

When you boost the energy level of the core, it can't get out until it busts out. And it is gonna get out. And en 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.

[A]

Oh, my goodness.

[B]

You thought your oatmeal spilled over the sun is basically spilling over out of its pot.

[A]

Wow.

[B]

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 gonna 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.

[A]

Right, Right.

[B]

Lower the heat, which the sun doesn't have the power to do. Now it can bubble, and you can cook the oatmeal.

[A]

So the sun has no choice but to go ahead, to keep expanding.

[B]

Correct.

[A]

Until it becomes its own delicious breakfast explosion.

[B]

Whereas you, the chef in the morning, have the option to lower the heat on the oatmeal.

[A]

Right.

[B]

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.

[A]

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[B]

Chuck.

[A]

Yes?

[B]

I got some obscure stuff to share with you.

[A]

My favorite obscure.

[B]

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.

[A]

Okay.

[B]

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 minding its own business in the atmosphere.

[A]

And then the airplane sucks it in.

[B]

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.

[A]

Oh, okay.

[B]

The space shuttle, which doesn't launch anymore, had two different kinds of fuel. You 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.

[A]

Interesting.

[B]

So if you have a toilet paper roll, remove the cardboard, and then you just start pulling on it.

[A]

Right.

[B]

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.

[A]

Right.

[B]

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.

[A]

Interesting.

[B]

Yes. That's how the solid rocket boosters work, by the way. Once they're ignited, you can't shut them off.

[A]

I hope you're igniting them at the right time.

[B]

And they're clamped down until they ignite, and then when they ignite, they break away because you can't. There's no stopping 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.

[A]

I think I'm hearing a little H2 and one H2 O. O.

[B]

How do you concentrate the most amount of this hydrogen gas and oxygen gas? You liquefy it.

[A]

Right.

[B]

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?

[A]

Well, it's got to be water.

[B]

Water. There it is.

[A]

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.

[B]

They call hydrogen fuel cells.

[A]

Okay. That's right.

[B]

Now, 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.

[A]

Together without blowing everybody up.

[B]

Right? Exactly.

[A]

A little like, oh, the humanity every other day.

[B]

Did you know that when Orson Welles did the radio play of H.G. wells's War of the Worlds.

[A]

Right.

[B]

He studied the vocal intonations of that announcer.

[A]

You're kidding me.

[B]

And copied them for the announcer who.

[A]

Saw the aliens making everything sound that much more dramatic and tragic.

[B]

And tragic and real and scary. Do you ever notice when it launches, a few seconds later, it executes? The what?

[A]

The roll. The roll program.

[B]

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 downrange.

[A]

Aha.

[B]

That's why every rocket you have ever seen launched doesn't just keep going up.

[A]

Right.

[B]

Ever stop and wonder when I was.

[A]

Younger and I would watch these launches because they were such a big thing and you had to watch them for. Even in school, I used to think, well, they're never going to make it to space. They're going sideways. Thank you.

[B]

That's an observant point to make. So it goes from 0 mph to 18,000 mph sideways.

[A]

Nice.

[B]

Because once the rockets stop.

[A]

Right.

[B]

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 downrange 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.

[A]

Right.

[B]

When what we call space in the zero G environment, when people go is orbit.

[A]

Right.

[B]

You go into orbit around Earth and they're not very high above Earth's surface. Couple hundred miles. That's it. That's the distance from New York to Boston.

[A]

Yeah.

[B]

Or New York to Washington, D.C. you could drive that distance in four hours.

[A]

Yep.

[B]

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, okay?

[A]

Bezos, Branson's billionaires Boys race.

[B]

That's Boys race. Okay.

[A]

Love it.

[B]

All right. Elon went into orbit, right? My man Elon knows what orbit is.

[A]

He knew that he had to get out of here.

[B]

He needs an escape hatch.

[A]

He was like, they're coming after me, coming after me. I'm planning for the future. I'm gonna find a way to get out of here. They're planning for the future.

[B]

When the pitchforks are coming.

[A]

Bezos and Branson, they. They can come back. They got a place to come back to. I know. I got to go.

[B]

So he. 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. 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 Brachistochrone problem, okay?

[A]

Now, you certainly are going deep. Now, this is a deep cut on the B side.

[B]

Let's have a. A round ball right? 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.

[A]

Yes.

[B]

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 Brachistochrone problem.

[A]

Nice.

[B]

And it requires sort of Hamiltonian representations of the energy of the system to solve it. Okay? The Bernoulli brothers posed these to each other. 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.

[A]

Oh, oh, oh, Watch out. Yo, that is a physics mic drop right there.

[B]

Yeah. So that's how to get into orbit the most efficiently.

[A]

It's very elegant, by the way.

[B]

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.

[A]

Nice. Oh, those Bernoulli brothers, you know, they were something at a cocktail party, that's.

[B]

For sure the life of the party. So unfortunately they never knew that this was also a rocket solution for them.

[A]

But that is really super cool.

[B]

All right, that's been another StarTalk explainer with my co host, friend and buddy Chuck.

[A]

Nice. Always a pleasure.

[B]

Neil DeGrasse Tyson here as always. Keep looking up.

[D]

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[B]

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