The aliens are coming to dinner! In this episode we wonder what food aliens might eat and talk to real scientists who've thought long and hard about this question. Plus, our friends at America's Test Kitchen show us how to whip up a delicious beef and broccoli dish. We'll lay out the cooking instructions step by step throughout the podcast so you can cook along. When the episode is over, you'll be ready to chow down.

Beef and Broccoli Stir Fry
Beef and Broccoli Stir Fry
Courtesy of America's Test Kitchen


This recipe comes from America's Test Kitchen's upcoming The Complete Cookbook for Young Chefs.

Serves 4
Prep Time: 15 minutes
Cook Time: 35 minutes

Prepare Ingredients

1 tablespoon plus ¼ cup water, measured separately
2 tablespoons soy sauce
1½ teaspoons cornstarch
¼ teaspoon baking soda
1 pound flank steak (substitute tofu for vegetarian option)
¼ cup hoisin sauce
2 teaspoons Asian chili-garlic sauce
1 tablespoon vegetable oil
6 cups broccoli florets, cut into 1-inch pieces
4 garlic cloves, peeled and minced

Gather Cooking Equipment

2 medium bowls
Cutting board
Chef’s knife
Rubber spatula
12-inch nonstick

Cutting Beef for Stir Fry

1. Use chef’s knife to cut steak with grain (long lines running length of steak) into 3 or 4 strips (each about 2 inches wide).

2. Cut each strip across grain into thin slices, about ¼ inch thick

Start Cooking!

1. In medium bowl, whisk 1 tablespoon water, soy sauce, cornstarch, and baking soda until combined.

2. Use chef’s knife to cut steak into ¼-inch-thick slices. Add sliced beef to bowl with soy sauce mixture. Wash your hands. Use rubber spatula to stir to coat. Let beef sit for 15 minutes.

3. While beef sits, in second medium bowl, whisk hoisin sauce, chili-garlic sauce, and remaining ¼ cup water until combined.

4. When beef is ready, heat oil in 12-inch nonstick skillet over medium-high heat for 1 minute (oil should be hot but not smoking). Use rubber spatula to carefully add beef to skillet and spread it into even layer. Cook, stirring occasionally, until beef is lightly browned on both sides, 2 to 4 minutes. Turn off heat and use rubber spatula to transfer beef to large plate.

5. Add hoisin mixture, broccoli, and garlic to skillet and return to medium high-heat. Cook, stirring occasionally, until sauce is thickened and broccoli is tender, about 5 minutes.

6. Stir beef and juices on plate back into skillet and cook for 1 minute. Turn off heat. Serve.  

Audio Transcript

Download transcript (PDF)

- You're listening to Brains On!, where we're serious about being curious.

- Brains On! is supported in part by a grant from the National Science Foundation.

SANDEN TOTTEN: Hey, Molly. If octopuses dressed their tentacles, do you think they'd wear pants legs or like sleeves?

MOLLY BLOOM: I think they'd wear an octo-glove.

SANDEN TOTTEN: Oh, yeah, that makes sense.

MARC SANCHEZ: Hey, is anybody expecting a fax?

MOLLY BLOOM: It's 2018, Marc. No one is expecting a fax.

MARC SANCHEZ: Well, this old fax machine here is totally faxing up a fresh new fax.

SANDEN TOTTEN: What does it say?

MARC SANCHEZ: Dear Brains On!, we love your show. Thank you. Heard you ask people what they'd serve aliens for dinner. Sounds good. On our way over, signed the aliens?

MOLLY BLOOM: The aliens?

SANDEN TOTTEN: They're coming? When?

MARC SANCHEZ: Oh, hang on. There's a PS. We're coming in 30 targlosecs, 40 if there's space traffic.

SANDEN TOTTEN: Space traffic?

MOLLY BLOOM: How long is a targlosec?

MARC SANCHEZ: PPS-- it says a targlosec is about a minute.

SANDEN TOTTEN: OK, wait. Aliens are legit coming over for dinner?

MARC SANCHEZ: Yeah, in 30 targlosecs. That's like a half hour.

SANDEN TOTTEN: This is big. This is real big. OK, we need to call NASA. We need to invite world leaders. We need to invite the United Nations, the media, Beyonce.

MARC SANCHEZ: We do not have enough plate settings for NASA and all the world leaders.

SANDEN TOTTEN: OK, just Beyonce then.

MOLLY BLOOM: Maybe we should keep this between us for now. We don't want to scare the aliens.

SANDEN TOTTEN: Or Beyonce could just have my plate, or we could share a plate. That's ridiculous. Or is it?

MOLLY BLOOM: OK, let's focus. We have 30 minutes to make a meal worthy of intergalactic guests. Marc, you set the table.

MARC SANCHEZ: I'm on it.

MOLLY BLOOM: Sanden, you clean up the dining room. Last I checked, it was still covered in spare robot parts.


MOLLY BLOOM: I am going to find a recipe. Time to get cooking.


Chill, chop, mix, heat. Reverse the order then repeat. Heat, mix, chop, chill, the recipe for every meal. Chill, chop, mix, heat. Reverse the order then repeat. Heat, mix, chop, chill, the recipe for every meal.

You're listening to Brains On! from American Public Media, and today we're talking aliens. Specifically, if aliens came to Earth, what food should we serve them? We've gotten a lot of great suggestions.

GABRIEL: If I fed aliens a dish, I would feed them Brussels sprouts because they might look like the same things as us.

ANA: I would feed the aliens a taco platter because they could have all sorts of things. Just think of it. There will be all the vegetables, like lettuce, onions, tomatoes, avocados, and peppers. Then you would have all that meat.

ABEL: I would feed an alien a banana because they're very healthy, and I think their radioactivity would give them extra strength.

NOAH: I would feed an alien zucchini because it is the color of most aliens and it is healthy.

TRISTAN: I would feed aliens green beans because they are green and aliens are green.

BELLA: I would serve them homemade minestrone because I think it's really delicious, and it has carbs and vegetables and everything to make you strong and healthy. And if you put in beans, it also adds protein.

BATSHEVA: I would give them Cheerios because they look like alien spaceships.

PRESTON: I would feed an alien pizza because every country has dough, tomato, cheese, and a heat source to bake the pizza.

MOLLY BLOOM: So many excellent ideas. That was Gabriel, Ana, Abel, Noah, Tristan, Bella, Batsheva, and Preston. Since this is part five in our team-up with America's Test Kitchen, I should check with them, too. They've helped us explain the science of heating, chilling, chopping, and mixing, and I bet they could help here, too.

- Hi, you've reached America's Test Kitchen.

- We test recipes in gear so you don't have to.

MOLLY BLOOM: Hey, is this Katy Laird and Molly Birnbaum? It's Molly Bloom from Brains On!.

KATY LAIRD: Yes, it's us.

MOLLY BIRNBAUM: Hey there, Molly. What's up?

MOLLY BLOOM: I need some help. I need a recipe for a guaranteed crowd pleaser of a meal. We've got some really important guests coming over.

KATY LAIRD: Is it Beyonce?

MOLLY BLOOM: Sadly, no.

MOLLY BIRNBAUM: Is it aliens?


MOLLY BIRNBAUM: Say no more. We've got you covered.

KATY LAIRD: We're going to search through our database of millions of five-star recipes and-- aha, perfect.

MOLLY BIRNBAUM: A killer beef and broccoli stir fry. This is a great recipe because it is super quick. It comes together in minutes, which is important because you want to be able to concentrate on your dinner guests, I'm guessing.

KATY LAIRD: Yeah. Plus it's great for skilled chefs and beginners alike. There's plenty to chop. There's plenty to mix together.

MOLLY BIRNBAUM: It also has really bright and fun flavors. So it's super delicious with hoisin and chili garlic sauce, and it's easy to prep. It's a perfect meal.

MOLLY BLOOM: This sounds really excellent. And, fortunately, there's beef and broccoli in Toby.


MOLLY BLOOM: That's our fridge. It's a long story, never mind.

KATY LAIRD: Cool. We'll fax you over the recipe.


KATY LAIRD: OK, it's on its way.

MOLLY BLOOM: Is faxing cool again?

MOLLY BIRNBAUM: You know, since this is such a straightforward recipe, I bet that your listeners could actually cook along. Just have them gather all the ingredients and then head to the kitchen with an adult. It should only take about 30 targlosecs.

MOLLY BLOOM: Wait, you know what a targlosec is? No, no time to get into that now. You guys are lifesavers. Thank you so much, Katy and Molly.

KATY LAIRD: Our pleasure.

MOLLY BIRNBAUM: Good luck with your meal, other Molly.

MOLLY BLOOM: As our friends at America's Test Kitchen mentioned, this celestial stir fry is perfect for chefs of all ages. We actually have the recipe on our website,, if you want to cook along. And we're going to start cooking. So if you want to join us, pause now. Get the recipe and gather the ingredients. Make sure an adult is helping out. Then unpause and follow along. Sanden, the recipe's here.


MOLLY BLOOM: I've got to host the show. Can you get the meal going?

SANDEN TOTTEN: Of course. This is perfect. I'll try out our new artificially intelligent voice assistant, HARVEY. [CLEARS THROAT] HARVEY, scan the recipe, please.

HARVEY: Scanning recipe.

SANDEN TOTTEN: HARVEY, will you please read the instructions to me as we go? I hate having to look at recipes while I cook. So I've taught HARVEY to read them to me and anticipate my every move, right, HARVEY?

HARVEY: Right, Sanden. I knew you were going to ask that. I anticipate everything.

SANDEN TOTTEN: So cool. How did people cook before--

HARVEY: People cook before, HARVEY? I anticipated that was what you were going to say.

SANDEN TOTTEN: This is awesome. Thanks, buddy.

MOLLY BLOOM: How did you come up with the name, HARVEY?

SANDEN TOTTEN: It's an acronym. It stands for hearing and reading virtually everything yo.

HARVEY: Step one, prepare your mise en place

SANDEN TOTTEN: Obviously I was going to do that, I mean, once I looked up what mise en place means.

HARVEY: I anticipated this. So here is a definition. Mise en place, French for putting in place. It means setting out all the ingredients before you start cooking.

MOLLY BLOOM: It helps you cook like the pros.

HARVEY: Peel and mince for cloves of garlic.


HARVEY: Mince? It means cut into very small pieces, like half a grain of rice.

SANDEN TOTTEN: Ah, yes. I knew that. On it. I love this thing. It's so cool.

MOLLY BLOOM: OK, while you're doing that, I'm going to do some more detective work on what aliens might eat. I've got the perfect person on the line. Her name is Allison Enright. She studies cool things like astrobiology and biogeochemistry at Rutgers University. Hey, Allison. Thanks for taking the call on short notice.

ALLISON ENRIGHT: No problem. What's up?

MOLLY BLOOM: Well, let's just say, hypothetically, aliens existed. And let's just also say, hypothetically, they were coming to your headquarters in like 20 minutes for dinner because they heard you talking about serving them food on your podcast. What kind of food should you be serving, hypothetically?

ALLISON ENRIGHT: Molly, are aliens coming over for dinner in 20 minutes?

MOLLY BLOOM: Maybe, a little. We just want to know if aliens did exist, would they even eat food at all? Does all life have to eat?

ALLISON ENRIGHT: Yes, everything needs an energy source to live.

MOLLY BLOOM: OK, so they probably eat. Maybe we should start there. How exactly does food give us energy?

ALLISON ENRIGHT: So when we eat food, we put it into our mouth, and it goes into our stomach where we secrete digestive juices that break that food down into its chemical components. Then as it travels through our small intestine and into our bloodstream, those chemical components are delivered to individual cells.

MOLLY BLOOM: OK, so our cells get energy from chemicals in our food. What specific chemical is it that we eat to get energy?

ALLISON ENRIGHT: We eat carbon in the form of sugar.

MOLLY BLOOM: Sounds delicious. So once that carbon is in our cells, how do our cells turn that into energy?

ALLISON ENRIGHT: They fix the carbon in place. They rip the electrons off.

MOLLY BLOOM: OK, pause. So Allison just mentioned electrons. What are those? Well, carbon is made of tiny building blocks called atoms. So am I. So are you. So are trees, rocks, and pretty much everything. These atoms are made of even tinier particles called protons, neutrons, and electrons. Electrons are super cool and a big part of how electricity works. As we know, electricity is a form of energy. So, Allison, you're telling me that our cells actually take the tiny electrons from carbon to get energy?

ALLISON ENRIGHT: Exactly. Transferring electrons releases energy. And the cells harness some of the energy released from that electron transfer to provide a power source. At a cellular level, that's pretty much what's happening.

MOLLY BLOOM: OK, so as long as something has electrons to spare, it could potentially power cells? But just because something can be food for one life form doesn't mean all life forms can eat it, right?


MOLLY BLOOM: So is there anything that simply just can't be eaten at all by any life form?

ALLISON ENRIGHT: Pretty much anything that doesn't have available electrons. They wouldn't make very good food sources. An example of that would be like argon gas or helium because they just don't have any electrons to donate, and they can't accept any.

MOLLY BLOOM: OK, so aliens could potentially eat lots of stuff, but no helium or argon gas. We'll keep those off the menu. Now, here on Earth, there are tiny lifeforms called microbes, and they eat some pretty crazy stuff. I heard scientists are studying these microbes because they could help us understand what aliens might eat, right?

ALLISON ENRIGHT: Yes. We're finding organisms deep within the Earth's crust. We're finding organisms at extremely high temperature and pressure conditions, and they're thriving. I think an example of one of the most extreme microbes on Earth is Deinococcus radiodurans, and it can tolerate dehydration. It can tolerate extremely low pHs, so very acidic conditions, as well as cold. And it actually eats radiation.

MOLLY BLOOM: Hold the phone. Radiation? How is that even possible?

ALLISON ENRIGHT: Well, there are electrons that can be released during the decay of radioactive substances, and they can be used by some bacteria as an energy source.

MOLLY BLOOM: You are blowing my mind. So, basically, life can eat all kinds of things. There's no way to know what an alien might eat.

ALLISON ENRIGHT: Well, an alien who managed to make it to Earth is going to be pretty smart and pretty evolved because they would have had to develop better technology than we have to even get here. So that alien probably has a pretty good idea of what it needs. If it was friendly, I would get out of its way and let it find what it needs.

MOLLY BLOOM: That makes sense. Well, we can still offer them a good meal. And if they can't eat it, at least they'll know we tried. Thanks for the science, Allison Enright.

ALLISON ENRIGHT: No problem. Good luck with your dinner party.

HARVEY: Cut the broccoli into small bite-sized pieces. Use the floret or the top part of the broccoli.


MOLLY BLOOM: Hey, by the way, if you want more recipes like this one for beef and broccoli stir fry, head to There you can sign up for the ATK kids newsletter. You'll also get hands-on activities and information on their upcoming cookbooks and straight to your inbox. And speaking of inboxes, ours is full of excellent questions like this one from Rosalia.

ROSALIA: My question is, how does gum stay chewy, and why doesn't it dissolve in your mouth like food?

MOLLY BLOOM: We'll answer that at the end of the show in our Moment of Um. Plus we've got a special shout out for all the kids who send us their drawings, mystery sounds, questions, and cool ideas. It's the Brain's Honor Roll. You can join, too. Just send us something by going to You know, we would love a drawing of this epic alien dinner party. What will the aliens look like? Did Marc put out fresh flowers? Is Beyonce there? It's your imagination. You can draw it however you want.

HARVEY: Cut the steak. First, cut with the grain into long strips.

SANDEN TOTTEN: What? HARVEY, please explain what you mean by--

HARVEY: Grain? The steak will have little lines in it. Cut the same direction as those lines. The strips should be about 2 inches thick.

SANDEN TOTTEN: Ah, I see. I don't really eat meat. But for the aliens, I'm willing to prepare anything.

HARVEY: Then cut those strips across the grain, cutting them into pieces about the width of your pinky finger.

SANDEN TOTTEN: Got it. Hey, HARVEY, what if the aliens don't eat meat?

HARVEY: You could use tofu.

SANDEN TOTTEN: What if they don't eat tofu? Either way, I'll eat it. Keep going. OK, I'm on it

MOLLY BLOOM: This is Brains On!. I'm Molly Bloom.

MARC SANCHEZ: And I'm Mark Sanchez. I got the table all set for the aliens. What's next?

MOLLY BLOOM: Well, Sanden's working on the stir fry. Everything's coming together. Maybe we should kick back with a little mystery sound action.

MARC SANCHEZ: Oh, man. I am so into this idea. Hit me, Molly.

MOLLY BLOOM: Here it is.


MOLLY BLOOM: Any guesses, Marc?

MARC SANCHEZ: Well, I'm going to say, since we're talking about food, that this might be food related.


MARC SANCHEZ: And the thing that comes to mind that is squeaky like that is, for me, is celery.


MARC SANCHEZ: Does it have to do with celery, maybe?

MOLLY BLOOM: That's a really excellent guess. Well, stick around. We're going to be back with the answer in just a bit. I'm getting hungry.

HARVEY: Prepare the sauce in a medium bowl. Add 1 tablespoon water, 2 tablespoons soy sauce. Put down your tablespoon. Now grab your half teaspoon and measure 1 and 1/2 teaspoons cornstarch.

SANDEN TOTTEN: 1 and 1/2? OK, that means three of these half teaspoons. Got it.

HARVEY: Now take your 1/4 teaspoon and measure out 1/4 teaspoon of baking soda. Now whisk it together.

SANDEN TOTTEN: Ha, I know the best way to whisk, HARVEY. Learned it from my friends at America's Test Kitchen. Side to side, not round around. Here we go.

HARVEY: Now add sliced beef into the bowl and mix it around so it's coated.


HARVEY: Let the steak sit. And now make the rest of the sauce in a different bowl.

SANDEN TOTTEN: OK, let me just grab a bowl.

HARVEY: Pour in 1/4 cup hoisin sauce, 2 teaspoons chili garlic sauce, and 1/4 cup water. Whisk it up.

SANDEN TOTTEN: I love whisking.

HARVEY: Ready to start the stir fry. Get a 12-inch non-stick skillet.

SANDEN TOTTEN: Got one. Mine's purple.

HARVEY: Pour in 1 tablespoon of oil and let it heat up over medium-high heat. This should take about 1 minute.

SANDEN TOTTEN: Why is there cornstarch and baking soda in the sauce anyway, HARVEY?

HARVEY: Cornstarch helps thicken the sauce, and the baking soda gives the beef a very smooth texture.

SANDEN TOTTEN: Ha, that's really cool.

HARVEY: Add beef to skillet. Cook, stirring occasionally for a few minutes until beef is lightly browned.

SANDEN TOTTEN: You know, I actually know why beef turns brown. I learned it in the heat episode of this series. It's thanks to the Maillard reaction.

HARVEY: You are very smart, Sanden.


MOLLY BLOOM: OK, so while we're busy finishing up our extraterrestrial eats, let's hear more ideas from you about what to serve aliens.

- I would feed an alien pizza because pizza is hot. And if he was from Venus, Venus is hot. So he would probably like it.

- What I would feed aliens that came to Earth would be pizza. You could put a lot of food on it, so it would give them a chance to taste a lot of different foods. And a lot of people like pizza, which means that they could kind of get a grip on what humans like in food.

- I would feed aliens cooked spinach because it's slimy, and I think they eat slimy stuff.

- And I would feed aliens soup because it's sloppy, and I think they would like it.

- I would feed aliens sundubu-jjigae, which is a Korean soft tofu stew. I love this stew a lot. This stew has a lot of textures. It is soft, the tofu, soupy, the broth, and chewy, the meat. I think aliens would think it is interesting.

- What I would give the aliens is fruit so they can taste and know all the fruits that grow in Earth.

- And what I would give the aliens to eat is Indian food because they have many different spices and it's yummy to eat.

- We think that the best food to share with guests on our planet is bread. It represents how humankind was able to grow into civilizations. When we learned to farm grains, our species went from hunter gatherers to agricultural people, allowing us to spend less time trying to find and catch food and more time for other things, like listening to podcasts, eventually.

MOLLY BLOOM: Thanks to Eli, Dorothy, Kaylin, Norah, Mia, Mathias, and Benjamin for those yummy-sounding ideas. Speaking of yummy--

HARVEY: Turn off heat and transfer beef onto a plate.

SANDEN TOTTEN: Roger that.

HARVEY: Now return skillet to stove. Add broccoli, garlic, and hoisin mixture. Turn the heat back on and stir occasionally for about five minutes.

MOLLY BLOOM: That is starting to smell delicious. You know, one way to think about feeding aliens is to try and imagine where they're from. Scientists have actually found distant planets that might be capable of supporting life. But what kind of life? And most important to us, what would that life eat? To help us think this through, we've got Diana Dragomir on the line. She's an astronomer with MIT. Hi, Diana.

DIANA DRAGOMIR: Hey, Molly. I would love to think about what aliens might eat.

MOLLY BLOOM: Great. So besides a random fact sent to a podcast show, do we have any actual evidence that aliens exist?

DIANA DRAGOMIR: Yeah. So just to be clear, we haven't yet found any aliens on other planets. But we do think they're out there just because life forms so easily on Earth. So we think-- astronomers think that life would form pretty easily on other planets as well.

MOLLY BLOOM: Gotcha. So you study far-off planets that orbit around other stars. How does that work?

DIANA DRAGOMIR: So we use very big telescopes, also very small telescope sometimes, to look for planets around other stars. Some of those telescopes are in space. Some of them are on top of mountains. Most of them are probably as big or bigger than your house, and that's how we detect those planets.

Now, when we look for planets that might host life, we started from the idea of, what is life here on Earth, because that's all we know. So we look for planets that are the size of the Earth and that have the same temperature as the Earth. And if possible, they have a star that's similar to our sun.

And we have found a few planets that seem to be similar to the Earth. But we have also found hundreds of planets that are very different from the Earth. So then we got really excited about that because maybe not all life in the universe is like life on Earth. And maybe you could have life on those crazy, crazy planets.

MOLLY BLOOM: What kind of planets are we talking about here?

DIANA DRAGOMIR: So, for example, some planets that we found are very, very hot lava planets. Other planets that we found are planets around two stars. And if you watch Star Wars, then that's kind of like the Tattoine planets. So those planets have two sunsets, two sunrises, sometimes like a 1 and 1/2 sunrise, all kinds of weird stuff going on in the sky.

We also have planets around very, very small stars compared to our star, planets that could be ocean planets, so just water all over the surface, a variety of planets, and among all of those, a few that are like the Earth.

MOLLY BLOOM: These planets around distant stars, they have a special name, right?

DIANA DRAGOMIR: Right. So planets around other stars are called exoplanets. Exo- means outside of something. So those are planets outside our solar system. We've started finding exoplanets 20 years ago. And since then, we found about 5,000 exoplanets, a lot of them.

MOLLY BLOOM: OK, so given what we know about these exoplanets, how should we be thinking about what to serve aliens?

DIANA DRAGOMIR: So I would think a little bit about where they're coming from. Where do they live now? And if they're coming to Earth, how might that be different from the place where they live now? So, for example, if you had a really, really hot planet that was like molten lava all over the place-- we found lots of those-- everything would be vapor.

So aliens would actually have to suck their food out of the air because nothing would be solid. They wouldn't be able to eat with knife and fork. So I may want to find a balloon for them and maybe put some vaporized food in it for them to suck out.

MOLLY BLOOM: Very interesting. So what about if they came from a planet covered in water?

DIANA DRAGOMIR: So you could think about that a little similar to the lava planet. And we may actually be more likely to find aliens on an ocean planet because it's a little-- we think it's a little easier to live there than in extremely hot temperatures. And there, aliens may take all of their food as smoothies or kind of like whales do. They always take in a lot of water with their food.

So that would be a little easier for me. I probably would just want to blend whatever food they like into a smoothie. There are planets that we're finding that are very, very cold. And, probably, a lot of things on those planets are solid and even frozen. So my guess is those aliens are eating a lot of frozen dinners. So they better have good microwaves.

MOLLY BLOOM: Do you think we could visit one of these planets in our lifetime to see if they have life?

DIANA DRAGOMIR: I don't think so. Even the closest planets to us are still several light years away. And what that means is that if you were able to travel at the speed of light, it would still take at least a few years to get there. And we don't yet have the technology to travel at the speed of light. Even if we did, you would have to worry about what's happening to your body and all kinds of weird things when you're traveling at the speed of light.

But there's a lot to do from the Earth and from our space telescopes, and I think that's going to keep us pretty busy.

MOLLY BLOOM: Well, thank you so much, Diana, for helping us think this through.

DIANA DRAGOMIR: Thank you guys for having me on the show.


MOLLY BLOOM: Let's see how that stir fry is coming along.

SANDEN TOTTEN: We're almost ready for the finishing touches.

HARVEY: Is the sauce thickened and the broccoli tender, Sanden?


HARVEY: Then add steak and juices from the plate back into pan and give a stir. Cook for 1 minute.

SANDEN TOTTEN: That smells so good.

MOLLY BLOOM: Should we have made noodles or rice to go with it?

SANDEN TOTTEN: Maybe next time. We don't have a lot of time, Molly. And besides, who knows? The aliens might be on like a low-carb diet or something. OK, they should be here soon.

HARVEY: I think it is ready, Sanden.

SANDEN TOTTEN: I think so, too. Thanks, HARVEY.

HARVEY: You're welcome, Sanden.

SANDEN TOTTEN: You know, HARVEY, I really--

HARVEY: Love you? I love you too, Sanden.

SANDEN TOTTEN: Uh, I was going to say I really learned a lot.


SANDEN TOTTEN: I mean, I love you too, HARVEY.

HARVEY: This is awkward. Powering down now.

MOLLY BLOOM: OK, food is ready.

MARC SANCHEZ: Table is set.

SANDEN TOTTEN: Robot parts are in the robot parts bin.

MOLLY BLOOM: Only one thing left to do. Let's revisit that mystery sound. Here it is again. OK, Marc, any new guesses?

MARC SANCHEZ: I'm kind of stumped. I don't know. I guess I'll stick with celery. But, Sanden, do you have any guesses?

SANDEN TOTTEN: Well, I have two guesses. I think it's either someone pulling Saran wrap out of a Saran wrap container. Or maybe-- have you ever drawn a face on a balloon? It kind of sounds like somebody drawing on a balloon with a marker. I don't know why.

MARC SANCHEZ: Yeah, it's like a twisting of a balloon, kind of a balloon animal thing, too.

SANDEN TOTTEN: Yeah, maybe it's a balloon animal.

MOLLY BLOOM: Oh, those are all very, very good guesses. Here is the answer.

- Hi, my name is [INAUDIBLE] from Columbus, Ohio. And that sound was the sound of me shucking corn. Shucking corn is when you pull off the husks plus the silk that's around the corn.

MOLLY BLOOM: Shucking corn.

MARC SANCHEZ: Oh, shucks.

MOLLY BLOOM: Wow. It makes a really good sound.


MOLLY BLOOM: Have you guys shucked corn before?

MARC SANCHEZ: Yeah, I love it. You know, we just got some guinea, pigs and they love to eat the corn husks.

MOLLY BLOOM: Well, that's great.

SANDEN TOTTEN: Whoa, that's like the best recycling you can imagine.

MARC SANCHEZ: I know. It's compost-- in-house composting.

MOLLY BLOOM: But, wait, guys, we are getting way off track. What time is it?

MARC SANCHEZ: Well, according to my watch, it's been 30 targlosecs.

SANDEN TOTTEN: The aliens should be here right about--


You think that's them? You think that's the aliens, guys?

- Yes, it's us, the aliens. Hello.

MOLLY BLOOM: All right, guys, ready to make contact?


MARC SANCHEZ: Yeah, I am so ready, Molly.

MOLLY BLOOM: All right, here we go. Dinner is served. All life as we know it needs a source of energy to survive.

MARC SANCHEZ: We get our energy by eating food and breaking it down into chemicals that help power our cells.

SANDEN TOTTEN: Some tiny lifeforms called microbes can even eat radiation.

MOLLY BLOOM: Scientists are using powerful telescopes to find planets in distant solar systems.

SANDEN TOTTEN: We call these exoplanets, and we found thousands of them.

MARC SANCHEZ: They are too distant to travel to, but scientists are finding other ways to search for signs of life.

MOLLY BLOOM: That's it for this episode, and we are going to sit down for dinner with the aliens. HARVEY, your turn.

HARVEY: Brains On! is produced by humans known as Marc Sanchez, Sanden Totten, and Molly Bloom, with help from Jacqueline Kim and Lauren Dee. They would like to thank Sam Choo, Caitlin Kelliher, and Denzel Beeland, plus extra special shout out to the solar system's finest food folks, America's Test Kitchen. To get out-of-this-world recipes and activities for young human chefs, head to Now, before we go, it's time for our Moment of Um.

ROSALIA: My name is Rosalia from San Diego, California. My question is, how does gum stay chewy, and why doesn't it dissolve in your mouth like food?

JULIE KORNFIELD: Hi, I'm Julie Kornfield. I'm a professor of chemical engineering at Caltech in Pasadena, California. So I study polymers, which are long molecules. They're the stuff that makes your skin elastic. It's the stuff that stores your genetic information. And chewing gum is made of polymers, and they make the gum very elastic.

It comes from the sap of certain trees. For example, chicle, in Latin America, comes from sapodilla tree. And the spruce tree makes spruce gum, which was used by the Wrigley family. So these long chain-like molecules can take different forms. They flow out of the plant as a liquid, but kind of a gooey one. And at that point, the molecules are still individuals. They can move past each other. They can take a new shape. And that's why if you swallow chewing gum, you'll be able to pass it through. But if you tried to swallow a rubber ball, it can't change shape. And so it'd be very hard to pass through.

So how does that happen? You start with these same very stretchy molecules. But in the case of the car tire of the rubber band, you link the molecules together. So if you could imagine a chain with 10,000 links in it, you end up creating something that would be like a spider web. So if you think about a car tire, it's essentially one really big molecule.

That's very different than the chewing gum, where you're just deforming the molecules, chewing, making them change shape when you press down with your teeth. But they are insoluble in your saliva. So you can chew gum all day, and it won't dissolve. The flavoring in it dissolves. Everybody complains about that. But the gum itself, it'll just stay elastic and chewy all day.

HARVEY: Molly, my battery is running low. Can you take over for a minute?

MOLLY BLOOM: Coming. Thanks, HARVEY. I'm going to chew through the latest group of fans to join the Brain's Honor Roll. These are the awesome people who power our show with ideas, drawings, mystery sounds, and questions. You can join them by going to Here they are. [LISTING HONOR ROLL]

HARVEY: Are the aliens nice?

MOLLY BLOOM: So nice, HARVEY. Come on. I'll plug you in to charge in the dining room so you can meet them.

HARVEY: Thank you, Molly.

MOLLY BLOOM: Thank you, HARVEY. And to all you listeners, we'll be back soon with more answers to your questions.

HARVEY: Thanks for listening.

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