Why are carrots orange? – Caden, 11, NC

Dear Caden,

When you picture the carrot section at a grocery store in the United States, you probably imagine rows of orange. But carrots can come in a rainbow of other colors: purple, yellow, red, and more.

And the first carrots weren’t orange at all. They were stark white.

That’s what I learned from Tim Waters, a Vegetable Specialist at Washington State University-Extension. He studies how to grow different kinds of vegetables, and helps others learn how to grow them too.

Carrots you eat today are domesticated. Domestication happens when humans tame wild plants or animals for many generations. Over a long period of time, people bred the carrot ancestors for traits such as sweet taste and attractive color.

Domestication helps explain how wolves became dogs, and how teosinte became maize. It’s also how a wild white root became sweet and orange.

“Before carrots were domesticated, they were believed to be white and very bitter and woody,” Waters said. “When people began domesticating them, the first types that were bred and fed upon by humans were purple and yellowish in color.”

Scientists think people first domesticated carrots in Central Asia around 1100 years ago.

Even though the first carrots weren’t as sweet as the ones you eat today, people probably weren’t eating the roots.

“It’s known that carrots were first grown primarily for seed and the uses of leaves,” Waters said. But as more colors emerged, the roots became tastier and became the more valuable part of the carrot.

We don’t know exactly when the first orange carrots appeared. But we have a good idea of why that color stuck around—simply because humans liked it.

“Orange wasn’t a naturally occurring color. It was kind of a genetic flaw, and then it was selected for,” Waters said.

One story says orange carrots became popular in the Netherlands in the 1600s. Orange became the national color, so orange carrots were supposedly associated with the royal family and William of Orange. But orange carrots probably weren’t bred by the Dutch. They just became more popular there.

Over time, orange carrots became the most common variety in some parts of the world. “That’s really why, in Western society, everybody perceives carrots to be orange,” Waters said.

But that orange color isn’t just for looks.

Orange carrots are packed with chemicals called carotenoids—specifically, beta-carotene. Your body turns beta-carotene into vitamin A, which helps you grow and protects you from getting sick.

Beta-carotene isn’t just nutritious. It’s also loaded with orange pigment. That’s why vegetables with lots of beta-carotene—like sweet potatoes, squash, and pumpkins—share the same color.

But what about that rainbow of other carrot colors? They have their own special qualities, too. Purple carrots get their color from loads of anthocyanin, a chemical that is healthy for your heart.

Carrot breeders have even created carrots with multiple colors. You can get the best of both worlds: a carrot that is orange on the inside, purple on the outside!

Sincerely,
Dr. Universe

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How was popcorn discovered? – Jalen, 12, Benson, N.C.

Dear Jalen,

There’s nothing like popcorn in progress: the snapping kernels, the warm buttery smell, and the knowledge that a delicious snack will be ready in minutes. It gives you some good time to think and wonder: how did humans first start doing this?

To find out where popcorn came from, I visited my friend Erin Thornton, an archaeologist at Washington State University. Archaeologists study how humans lived in the past—including the things they ate.

To learn the story of popcorn, we have to trace the history of maize.

Maize is another word for what you think of as corn. Humans grow it all over the world today, but it all started in Mexico.

Long before maize, there was a plant called teosinte (tay-oh seen-tay). If you saw teosinte in person, you probably wouldn’t guess it’s the grandparent of your popcorn. “It doesn’t really look like modern maize at all because it lacks large cobs—instead it looks more like a weedy grass,” Thornton said.

But over time, ancient people selected teosinte plants with softer and larger numbers of kernels. Over many generations, this resulted in the plant we know as maize.

Many scientists think all the first corn was popping corn. It was very important to the people who made it. The Aztecs used popcorn for both decoration and for eating. They also had a word, “totopoca,” for the sound of popcorn popping.

The Maya even tell stories about humans being created from maize. “It speaks volumes about how important this crop was to people who lived at that time,” Thornton said.

Popcorn is easily destroyed, so it can be hard for archaeologists to find it after hundreds or thousands of years. But the oldest popcorn ever found comes from a cave in New Mexico, estimated to be 5,600 years old. (Not quite as fresh as your popcorn, straight out of the microwave.)

We don’t know exactly who first discovered that popcorn can pop. But it’s a process that would have happened when people first started mixing dried kernels and heat.

Popcorn pops through interaction with heat. If you’ve ever looked at popcorn kernels before popping, you know they have a very hard outer shell. The insides are very hard too—until heat touches them.

When heat meets the natural moisture in the kernel, it creates pressurized steam within the shell. This steam softens the kernel’s insides. That heat and pressure increases, until the kernel can’t hold it anymore. And then pop! It explodes.

With that pop, the pressure in the kernel suddenly drops. The steam expands. All that inner goodness puffs out. That’s why popcorn looks like a little cloud.

We don’t know if the first popcorn-makers used flavorings. But when European colonists first learned about popcorn, they enjoyed eating it with milk and sugar like cereal!

Thornton told me white cheddar is her favorite popcorn flavor. Which kind do you like best?

Sincerely,
Dr. Universe

Dr. Universe: What is inside a blade of grass and why is it green? Green is my favorite color. We really like reading your articles in our newspaper. – Luke, 5, Ogden, Utah

Dear Luke,

I’ve been wondering the same thing lately.  Every time I go on walks, I notice new splashes of color. Watching bugs in the grass, I pretend they’re crawling through a jungle. Everything is bright and bursting with green.

When I saw your question, I knew Michael Neff would know the answer. Green is his favorite color, too. (In fact, when we talked over video, he wore a green Hawaiian shirt.) Neff researches plants at Washington State University, and he is especially curious about grasses.

If you chopped a piece of grass and looked at it with your eyes alone, you might not see much. But if you looked at it under a microscope, you’d see tiny structures containing even tinier parts.

All living things—you and grass included—are made of cells. Cells are like little building blocks with different jobs. Every blade of grass is made of millions of them.

Plant cells contain a smaller part called a chloroplast. “Chloroplasts look like fat sausage-shaped balloons,” Neff said.

Chloroplasts have a special job: making food. Grasses can’t search for food like animals can. So instead they make it themselves, taking in sunlight and carbon dioxide.

“Food for a plant is a combination of sunlight and carbon dioxide together,” Neff explained. “And the chloroplast is the factory that turns those two pieces into energy.”

But where does the green color come from? Something else inside the chloroplast is responsible: a special pigment called chlorophyll.

Your eyes see color based on light. Many different colors make up sunlight, and objects either absorb or reflect them. When light gets absorbed, you don’t see its color. But when light reflects off objects, including grass, the color reaches your eyes so that’s what you see. That’s why the sky often looks blue. It’s absorbing all the other colors of light, except blue.

The same thing happens with chlorophyll. “Chlorophyll does a very good job of absorbing all colors of light except for green. When we look at the blade of grass, we’re seeing green light being reflected off the blade of grass,” Neff said.

But maybe you’ve noticed grass isn’t always green. Depending on the time of year and where you live, different grass grows at different speeds. Here in Washington, most grass grows in the cool spring and fall weather.

Spring grass looks especially green because it contains new cells. New cells have tons of chlorophyll, reflecting green light.

In the summer and winter, grass might turn brown or yellow. It’s still alive. It just doesn’t have as much chlorophyll. It isn’t putting as much energy into new growth.

But when spring returns, so do the ingredients for growth—lots of water, light, and carbon dioxide. The grass takes it all in, making new cells full of chlorophyll. The cycle begins again.

Tiny blades sprout. Patches of color creep in. And before you know it, green surrounds you everywhere you look.

Sincerely,
Dr. Universe

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What is a sinkhole? What causes one? – Kathrine, 12, Calgary, Canada

Dear Kathrine,

Sinkholes can be scary to think about. They don’t happen too often, but when they do, they can take people by surprise. The solid ground disappears, and a hole suddenly appears.

It might seem like sinkholes appear out of nowhere. But they actually need specific conditions to form.

To have a sinkhole, you first must have a cave.

“You can think of a sinkhole as the end of the life cycle of a cave,” Kurtis Wilkie explained. He teaches Geology at Washington State University. He is very interested in how Earth’s features form over long periods of time.

A lot happens underground that we can’t see. Dirt and rock layers lie beneath our feet. Water flows around them, shifting and moving these layers.

With the right type of rock, enough water, and a lot of time, a cave can form.

Wilkie said caves often occur in rock called limestone. Limestone is made mostly of calcium carbonate (the same substance that makes up seashells!).

Limestone isn’t a very strong type of rock. It’s full of tiny cracks. They’re hard to see, but big enough for water to run through. Lots of contact with water can make those gaps get bigger. Over time, the limestone dissolves and breaks apart. This process is called erosion.

As the rock dissolves, empty space gets left behind. Eventually, that space gets bigger and bigger until a cave forms. This happens extremely slowly, much longer than any human’s lifetime.

“We’re talking not just thousands of years, maybe millions of years. It’s not as if you start the process now and then 10 years or 100 years from now you have a cave. It takes a very long time,” Wilkie said.

Most caves remain caves. But if water continues to interact with limestone, it can keep slowly eroding. The cave’s roof can become too weak to hold the heavy ground above it. If the roof collapses, the ground above it falls through. That’s how a sinkhole happens, and part of the cave comes to an end.

A sinkhole is the end of a cave’s life—but not every cave’s life. Most caves don’t ever collapse or turn into sinkholes. A sinkhole only happens if the cave’s roof becomes too thin and unsupported. Humans can cause sinkholes to happen more than they would naturally by pumping water from underground, reducing support for the ground above.

Sinkholes happen more in some places than others. You might hear about sinkholes in Florida, an area with lots of limestone. But here in Washington State, where I live, other types of rock abound. So sinkholes are very rare.

The odds of the ground collapsing beneath you are very small. You’re much more likely to get to visit a cave someday.

And if you do, you can look up at its walls and remember the forces that shaped it. All it takes is a special rock, a lot of water, and plenty of time.

Sincerely,
Dr. Universe

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Where does the universe end? – Oriah, 8, Pullman, Wash.

Dear Oriah,

When you look up at the night sky, it can feel like the universe is a big blanket of stars above you. But unlike a blanket, the universe doesn’t have corners and edges. Far beyond what humans can see, the universe keeps going. As far as humans know, it never stops.

When I saw your question, I went straight to my friend Michael Allen to learn more. He is a Senior Instructor of Physics and Astronomy at Washington State University.

The universe is bigger than the biggest thing you’ve ever seen. It’s bigger than the biggest thing this cat can imagine. It’s so big that even your question has more than one very big answer.

Allen explained that you can think of the universe kind of like a rubber band. If you look at a rubber band’s flat surface, you can see it has no beginning and no end. It keeps going around and around in a loop.

Imagine you drew dots on that rubber band. If you pull on the rubber band, what happens? The rubber band stretches, and the dots move further apart. The universe is like that. The distance between all its galaxies, planets, and stars is stretching all the time, like dots on a rubber band. It never ends, but it’s also constantly expanding.

Scientists don’t think there is a true edge of the universe. But there’s an end to what humans can see of the universe. This is called the edge of the observable universe. It’s the farthest we can see, based on how we get information from light.

Everything you see depends on light bouncing off objects. Light reflects off the things around you and your eye absorbs it. When you look at your hand, you see your hand in that exact moment.

But when you look at a star, you’re actually seeing that star in the past. That’s because the light has to travel a very long time to reach your eyes. The farther away the star, the longer it takes. It takes light from the nearest star, the Sun, eight minutes to get to our eyes. Light from the next nearest star, Proxima Centauri, takes about four years to get to us!

Light moves very fast — about 186,000 miles per second — but the universe is very big. So the farthest edge of the observable universe is the oldest light we can see: about 13.8 billion years in the past.

But that edge is just what we can see from Earth. But that’s just what we can see from Earth. Earth isn’t the center of the universe. It’s just one location. The edge of the observable universe depends on where you are. If we were somewhere else in the universe, we would have a different view.

No matter where you are, you can think of yourself as a time traveler of sorts. When you gaze up at the stars, you’re looking up at the past.

Sincerely,
Dr. Universe

Why do I like buffalo wings and not broccoli? – Joe, 10, New York City, NY

Dear Joe,

You’re not alone—cats don’t like broccoli much either. As a carnivore, I think a nice, meaty buffalo wing sounds great.

But humans are omnivores, meaning they eat both plants and meat. They’ve developed a taste for all kinds of things growing and living all over the world. So where do individual people’s preferences come from?

To find out, I visited Carolyn Ross, a professor of Food Science at Washington State University. Like you, she is very curious about why people like the foods they like.

You probably got part of your preferences from your human ancestors. Humans tend to seek the taste of fat, sugar, and salt. These ingredients are more scarce in nature, but abundant in foods we cook today. (That’s why it can be hard to stop at just one buffalo wing.)

Your individual experiences shape your tastes in a big way. If you’re familiar with a food and have good memories of it, you’re more likely to keep eating it.

But your genes also have an impact. Genes are like instructions written inside the body, which you get from your parents. They affect all kinds of things about you, including the way some foods taste. That’s why some people think cilantro makes a great addition to tacos, and some think it tastes like soap.

Your genes might even make you a “supertaster”—someone very sensitive to bitter tastes.

Your tongue is covered in little bumps called tastebuds. Tastebuds help you sense the flavor of what you’re eating. Humans’ tastebuds can detect five basic flavors: sweet, bitter, salty, sour, and umami (a savory, meaty taste.)

Supertasters have more tastebuds than most, making them more sensitive to different tastes. About 25% of people in the U.S. and Canada have a supertasting tongue. It’s possible you’re one of them.

Supertasting might seem like a superpower. “But being a supertaster is a gift and a curse because you’re very sensitive,” Ross said. Sweet things taste sweeter, but bitter things taste much more bitter.

Broccoli is one of the foods supertasters tend to dislike. “Supertasters find broccoli to be more bitter than people who are not supertasters and may eat less of it, at least when they’re younger. They also find cheddar or aged cheese to be exceptionally bitter. Their food choices are somewhat based on that,” Ross said.

If you’re a supertaster, you might always find broccoli to be too bitter. Even regular tasters find there are some foods they never love. To this day, Ross doesn’t like raw broccoli.

But your tastes might also change over time. It takes about six tries before your like or dislike for a food becomes a stable preference. So give it a few more tries. Check in with your tastes now and then. You might find a food you once hated eventually becomes enjoyable.

As a cat, though, my taste buds can’t sense sweet things. I’ll never know what you humans like so much about donuts.

Sincerely,
Dr. Universe

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