Dr. Universe: Why are some berries poisonous? Where does the poison come from and how does it get in the berries? – Bianca, 4 1/2, California  
  
Dear Bianca,  
 
A lot of living things on our planet have defenses they use in the wild to help them survive. For some plants, being poisonous may help keep them from becoming someone’s dinner. 
 
That’s what I found out from my friend Wendy Hoashi-Erhardt, a scientist who directs the Small Fruit Plant Breeding program at Washington State University.  
 
Berries like deadly nightshade, holly berries, and snowberries—just to name a few— are not safe for humans to eat. These kinds of plants naturally produce poisonous compounds in their berries.  
 
You may remember that everything in our universe, including berries, is made up of atoms. When the atoms come together, they form compounds. Those compounds can sometimes form in a way that interfere with the work your body’s cells are doing to try and keep you healthy.  
 
In fact, the poison from some berries may make insects, birds, animals, and even humans really sick. That sends a kind of message or reminder to those creatures to avoid the plant and its berries in the future—or else they’ll likely get sick again.  
 
Humans have even discovered different types of compounds in different berries that can make us sick. For instance, there are the toxic compounds in snowberries and holly berries called saponins. Meanwhile, deadly nightshade contains compounds named trophine, scopolamine, and hyoscyamine.  
 
Throughout history, humans have actually learned quite a lot about which plants are dangerous to eat versus which ones are good to eat.  
 
For the nutritious and delicious plants, humans have been able to take those plants and make them even more useful through a process called plant breeding, Hoashi-Erhardt said.  
 
For example, we can take a raspberry and blackberry and cross them to create an entirely new berry called a tayberry. 
 
Hoashi-Erhardt does a lot of work helping us breed raspberries and said scientists have different categories for what we call “berries.” Part of what makes a berry a true berry has to do with an organ in the plant called an ovary.  
 
A raspberry, for instance, grows from a single raspberry flower. But that flower has many ovaries and they become all the little segments, which are called drupelets, that make up raspberry. It turns out a raspberry is not a true berry even though we call it a berry. 
 
Meanwhile, a blueberry comes from a single flower with just one ovary. Scientists call these berries that come from just one plant ovary “botanical berries.” True berries grow from a single flower with just one ovary. I was surprised that means bananas and cucumbers are technically true berries, too. 
 
It’s great to hear you are curious about berries, Bianca. They are truly an interesting part of the plant to observe. It’s also important to learn which types of berries are safe to eat and which are not. You can’t tell just by sight; becoming familiar with edible species of berry plants happens by talking to a botanist or carefully studying a field guide to wild edible plants.      
 
Sincerely, 
Dr. Universe

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Dr. Universe: Why do trees grow so slow? – Ana, 7, Covert, MI

Dear Ana,

When you eat food, you get a lot of important nutrients that help you grow. The trees that live on our planet also need some nutrients to grow.

Trees use their leaves to help capture energy from the sun to make their own food. But as you may have noticed, a lot of trees lose their leaves during certain times of the year.

Without leaves, they can’t make nearly as much food, and without those important nutrients, they can’t grow very fast.

That’s what I found out from my friend Tim Kohlhauff, a certified arborist and urban horticulture coordinator at Washington State University. He is very curious about the lives of trees.

“These trees only get to make food part of the year,” he said.

Usually, we see slower growth in these trees between March and October. Of course, maybe you are thinking about the kind of trees that do not lose their leaves, like pine trees or evergreens. When it is really hot or really cold out, these trees will also experience slower growth. They may be trying to save energy and make it through tough times.

For instance, in the redwood forests of California where some of the tallest trees on our planet live, a redwood tree might grow two or three feet a year. But if the trees are stressed or don’t have water and sunlight, they might grow just an inch per year. Trees are pretty good at adapting to changes in their environment.

Not unlike humans, a lot of trees that live in forests grow faster in their younger years, too. In the forest, it can be a bit of a race to the top. There is a lot of competition between trees to grow tall so that they can get enough sunlight. After all, that sunlight is where they get energy to make their food.

While most humans don’t grow much taller after they reach ages 18 or 20, some trees can grow for up to 100 or 200 years. One slow-growing tree is the magnolia tree, which can reach heights of about 60 to 80 feet and sometimes even 100 feet tall. These trees can grow about one foot—the length of a ruler—a year.

Meanwhile, some trees will grow slowly but may never get very big. Dogwood trees only reach about 15 to 20 feet tall and grow about a foot a year.

Some trees may grow slowly, but they don’t grow forever. At a certain point, they stop growing taller and start growing wider. Not only does the trunk itself get wider, but the branches also grow out around the tree to form its canopy.

You know, we are still learning a lot about how the ways that the thousands of species of trees on our planet grow. But one thing we do know is that at least for some trees, growing slow and steady is just the right pace.

Sincerely,
Dr. Universe

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Dear Dr. Universe: How do you learn something hard? – Kai, 12, Alaska

Dear Kai,

There are so many different things we can learn in our world, but that doesn’t mean learning is always so easy. Maybe you want to learn a process, like how to complete Rubik’s cube, code an app, design a solution to a problem or answer science questions.

My friend Sarah Fick, an assistant professor of science education at Washington State University, was excited to hear your question. She said one way to learn something hard is to ask a lot of questions of yourself and other people.

Questions like: Why is it hard? Are you trying to remember something? Are you trying to understand how it works? Are you trying to solve a problem that’s hard to solve? Can you design something or come up with an idea that will help you solve that problem? Where can you find more information about your problem or who can you ask about it?

“Depending on what experiences you’ve had in learning—and the knowledge you’ve gained from your family and community—you are going to come at these problems with your own strengths,” Fick said.

Things that are easy for you, might be hard for someone else or the opposite could be true.

Fick reminded me that while we can learn a process, we can also learn more about how a process works. That’s what scientists do—they help us bring deeper knowledge into the world.

Through collecting data, researchers can help us build on current knowledge to create new knowledge. Another thing scientists do is create a model or draw a picture showing how they think the process works. A model can sometimes help us understand what we know and what we still have questions about.

When you are learning something hard, it also helps to ask yourself what is motivating you to learn. Maybe the motivation is that you want a good grade on a test. We call that extrinsic motivation. But maybe you want to learn how to do something for, well, you. Then, you have intrinsic motivation. When motivation comes from within, it often helps us learn.

Finally, while it may feel frustrating to learn difficult subjects or tasks, that’s sometimes a good sign. You might just be wrestling with knowledge that’s new to you and might be on your way to an “Aha!” moment when you gain a better understanding.

One of the areas Fick researches is helping us better understand how students can use their knowledge from one subject, such as math, to help them learn more about another area, like science. Learning often happens when we find connections, including connections to our daily life.

There are a lot of different factors that go into learning something hard, and these are just a few. The next time you find yourself facing a learning challenge, take a deep breath, ask yourself some good questions and get ready for the next step on your learning journey—wherever it takes you.

Sincerely,
Dr. Universe

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Hi Dr. Universe. My questions are: Why are people most commonly right-handed? Who/what deicides if we are left-handed or right-handed? Are you left-handed or right-handed? Thanks, Mya, 8, Alexandria, VA

Dear Mya,

We don’t know exactly why so many people are right-handed, but one place we might look for answers is in the material that makes a person who they are: genes.

The genes in your body help control all sorts of things from the color of your hair to your skin to your eyes. These traits can be passed down through generations—from grandparents to parents to you.

My friend John Hinz, who is a right-handed professor at Washington State University, knows a lot about genes and the study of how organisms pass their genes through generations.

He said that while there isn’t a single gene that helps determine if you will be right-handed or left-handed, scientists have found around 40 genes that seem to be related to handedness. Sometimes there is just one gene that causes a certain trait, but often it is combinations of genes that contribute to each of your characteristics.

“Genetics is clearly part of it but not the whole story,” Hinz said.

He also said when both parents are left-handed, they are more likely to have a child who is also left-handed. Some studies have shown that if both parents are right-handed, there is a 10% chance of having a child who is left-handed. Meanwhile, if both parents are left-handed, there is about a 25% chance the child will be left-handed.

But all we have to do is look at twins to realize there is more to it. Identical twins have all the same copies of every gene, but they don’t always use the same hand.

This question has left a lot of researchers wondering about the very question you’ve asked, Mya. People have looked into how the language centers in our brains might be connected to our handedness or how our experience as babies might be connected to our handedness. Some researchers have even observed dominant hands as a fetus develops in a mother’s womb.

They’ve also investigated how people’s different abilities are connected to handedness. Of course, just because there are a lot of connections or correlations between what hand a person uses and other traits or behaviors, that doesn’t mean we can say for certain. We haven’t found a clear answer to your question. Yet.

Whether you are left-handed, right-handed, or both-handed, hands can be really helpful tools. They can help us pick up things, climb to great heights, and even give a high-five. Perhaps one day you can join the community of creative and smart scientists to help us investigate more about genetics and handedness. There’s still a lot of research to do among our four-legged animal friends, too. As for me, I’m a righty. How about you?

Sincerely,
Dr. Universe

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Dear Dr. Universe: How did people figure out how much a whole planet weighs? They could not have just put it on a scale! How did they do it? – Angel, 14, California

Dear Angel,

About 300 years ago during another pandemic, there was a person named Sir Isaac Newton who spent a lot of time at home thinking about the universe.

He was thinking about how objects fall and started to wonder if the same force that made objects fall also kept the moon in its orbit. He called this force gravity.

That’s what I found out from my friend Guy Worthey, an astronomer at Washington State University. Gravity plays a big part in the answer to your question, and we’ll explore that in just a moment.

When scientists talk about how much planets “weigh,” they often talk about mass. Worthey reminded me that all objects—from cats to planets—have mass. Mass is the amount of matter that makes up an object.

Worthey told me astronomers can measure a planet’s mass using what we know about gravity. He said one planet that taught us a lot about the relationship between mass and gravity was Pluto.

“I remember when I was a kid, the textbooks said that Pluto was twice the mass of Earth,” Worthey said.

The mass of Earth is a whopping 5,970,000,000,000,000,000,000,000 kilograms—in pounds we’d write that out as 13,170 followed by 21 zeroes. When Worthey was growing up, scientists were using clues about Pluto’s brightness to make some educated guesses about its mass. But it wasn’t until they discovered Pluto’s moon that it gave them a chance to do some more calculations.

When there is an object around a planet, such as a moon or a satellite, we can study how that planet pulls on the object. We can use our understanding of this gravitational force to help discover the planet’s mass.

When scientists discovered Pluto’s moon, Charon, they learned about not only the pull Pluto had on Charon but also the size of the moon’s orbit and how long it took the moon to orbit around Pluto. They needed to use all of this information in their calculations to figure out Pluto’s mass.

It turned out that Pluto was much smaller than they had originally thought. Instead of being twice the mass of Earth, they found Pluto had a mass that was 1/200 the mass of Earth.

It turns out some planets, such as Venus and Mercury, do not have an orbiting object like a moon. It wasn’t until humans were able to send satellites to these planets that we were finally able to gather precise information about gravity and learn about mass.

You know, gravity is an important force. It’s what makes things fall. It’s what keeps planets in orbit. It’s what keeps us on the ground. While we may not have a scale to weigh planets, we can use what we know about gravity and mass to make all sorts of calculations and investigate questions about our universe.

Sincerely,
Dr. Universe

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Dr. Universe: How do fish migrate and why? – Norma, 10, Indiana

Dear Norma,

While a lot of fish swim from one region to another to find food or have babies, different fish species migrate in different ways.

That’s what I found out from friend Steve Katz, a professor at Washington State University who knows a lot about our planet’s natural resources and has researched fish such as steelhead trout, tuna and seven-gilled sharks in the Pacific Northwest.

He said that steelhead trout often navigate through the water with help from a sense of smell. Steelhead trout use their nostrils to pick up on chemicals from rocks that have dissolved in the water. The differences in the scents of the water help them know which river or stream to follow.

This is a helpful tool, especially as steelhead trout can swim for long distances over the course of a few years—in some cases, over 1,300 miles upstream after they swim through the ocean for more than 3,700 miles.

Katz reminded me that not all fish migrate. For instance, some of the steelhead trout males will stay behind in the streams when the females and other males head for the ocean. There is some risk in traveling long distances, so it can pay off for some fish to stay home and wait for the females to return.

If you think a few thousand miles is a long way to swim, wait until you learn about tuna. Albacore tuna cross the Pacific Ocean twice a year cruising at speeds of 5-10 miles per hour. In a lifetime, that might add about 20 to 25 round trips. When it comes to migration, these fish are marathoners.

“It’s spectacular,” Katz said. “Tuna are elite swimmers because they’ve got this extra red muscle and machinery that helps them swim at a steady, fast pace.”

A fish that moves much slower is the seven-gilled shark. These fish live where the saltwater meets the freshwater, or often where rivers meet the ocean, which we call an estuary. But when it starts raining a lot in the winter, there isn’t enough saltwater in the estuary anymore. They have to head out into the ocean.

The sharks travel up and down the coast for anywhere from 100 to 1,000 miles while they wait for the estuary to become saltier, and then they make their journey home for the summer.

Katz said that some research has also explored how fish might use Earth’s magnetic field—which extends from our planet’s interior out into space— or the angle of the sun to know which direction they should be going. But the truth is, scientists are still learning a lot about exactly how fish navigate the waters on their migration.

Perhaps you can find a species of fish that lives in your state and learn more about its migration journey. The more species you learn about the more you’ll realize just how many migration stories there are to discover.

Sincerely,
Dr. Universe

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Dr. Universe: How do horses sense how you feel? –Taylor, 11, New Zealand
 
Dear Taylor,
 
When I got your question, I called up my friend and veterinarian Dr. Macarena Sanz who had just finished checking up on the horses at the Washington State University Teaching Hospital. She was happy to help.
 
“It’s a hard question to assess scientifically,” Sanz said. “But I think everybody who has worked with horses can tell you that horses really do have a certain sense about humans.”   
 
One part of the answer to your question is that horses may be able to respond to a situation using clues from both a person’s facial expression and the emotion in their voice.  
 
In a study from Japan, researchers showed horses some photos of humans with different expressions on their faces, such as happiness or sadness. Along with the photos, the horses also listened to recordings of human voices.
 
Sometimes the voice and facial expression matched, for example, a happy face with a happy voice. But other times the horse might have seen a photo of a happy expression but heard a sad voice.   
 
“Horses were able to pick on that,” Sanz said. “When the horse didn’t feel like things matched, they would stare at the screen a lot longer.”
 
It kind of makes you wonder what exactly the horses must have been thinking. These kinds of studies will help researchers start to put together a better picture of how horses respond to humans.
 
You know, your question also made me curious about the ways humans figure out what horses are feeling. It turns out that horses have 17 expressions they can use to communicate, such as puckering their lips or dropping their jaw. Some expressions communicate they are in pain.
 
If you’ve ever stubbed your toe or broken a bone, maybe you know that feeling that makes you scrunch up your face in pain. That’s a kind of expression called a grimace.
 
Sanz said veterinarians use a scale called a grimace scale, which includes photos and information about different horse expressions and behaviors, like when they hold back their ears. It’s a tool many veterinarians who work with horses will use in their careers.
 
“I remember when I was starting my career, my boss would come in and say, ‘Oh, this horse has –that look–and it’s going to need surgery’ and she was right. The horse needed the surgery. And now I can see that look too,” she said.
 
While humans and horses have been a part of each other’s lives for thousands of years, there is still a lot to learn. Sanz said it’s likely we will continue to learn even more about the way humans and horses interact, especially as many studies have been showing that these interactions can have lots of health benefits.
 
Perhaps one day you’ll be a veterinarian who helps us provide the best care for horses or a researcher who helps us better understand the ways in which horses sense the world.
 
Sincerely,
Dr. Universe

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Dr. Universe: How do worms help protect the dirt? -Fisher, 7, Palouse, WA
 
Dear Fisher,
 
Worms can help the soil in a few different ways. One helpful thing worms do is move around different materials, such as leaves and grasses, and make holes in the soil.
 
That’s what I found out from my friend Lynne Carpenter-Boggs, a soil scientist at Washington State University, who was happy to help with your question.
 
“Worms are actually very strong,” Carpenter-Boggs said. “They can break through soil and make holes that allow air, water and plant roots to follow those channels.”
 
As the worms wriggle down into the earth, sometimes they also pull leaves and dead grass down into their burrows. These materials can break down and add important nutrients to the soil.
 
Meanwhile, worms sometimes bring leaves and grasses down into their burrows to save as a snack for later. For earthworms, soil is almost always what’s on the menu for breakfast, lunch and dinner.  
 
Worms eat all kinds of things in the soil. Scientists often call these things organic materials. This includes grasses, leaves, roots and other materials that make up the soil.
 
After worms digest their food, they poop. It turns out there is a particular word scientists use when they talk about earthworm poop: castings. These castings look pretty much like the dark soil and blend right into the mix. Castings are also a kind of natural fertilizer that can help plants grow.
 
We also find another important thing in the castings that help the soil: bacteria. Bacteria are so small we’d likely need a microscope to see them, but they also help with soil health. Different bacteria have different jobs in the soil.  
 
Some bacteria help break down—or decompose— different organic materials. There are even some bacteria that give off the very chemicals that create that earthy soil smell. Just as various types of bacteria live in your gut, a range of bacteria also live in the guts of worms.  
 
“We can see that there is this incredible diversity of bacteria in the earthworm stomach,” Carpenter-Boggs said.
 
Through digging holes, moving materials around, eating and dropping their castings, worms do a lot to help protect the soil.
 
When you think about it, the soil is a pretty amazing material. Soil gives worms what they need to survive, and the worms help give the soil what it needs to thrive. That’s great for animals and humans who eat plants that grow in soil, too. 
 
The next time I go outside, I’m going to take a closer look at the soil. Maybe you can try it out, too. Perhaps you will see some rocks, roots, grasses or maybe even a wriggling earthworm. If you have a magnifying glass, you might be able to get an even closer look. Take some time to think about how important the health of the soil is to all the life that lives in it—and how important soil is to all life on our planet.  
 
Sincerely,
Dr. Universe
 
P.S. Dr. Universe is looking for questions for an upcoming Northwest Public Broadcasting program! Do you have a science question about plants, fruits, or flowers? Or a question about rocks, volcanoes, or earthquakes? Guardians can send an e-mail to Dr.Universe@wsu.edu with the subject: Meet the Scientists to find out more!

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Hey, Dr. Universe: Why do we humans get sunburns when we are out in the sun too long? – Gavyn, 13, Indiana

Dear Gavyn,

Humans need sunlight to help keep their bones, blood and other body systems healthy, but too much time in the Sun can sometimes leave people with a sunburn.

Sunburns often strike when the body gets too much of a type of light, called ultraviolet light, from the Sun. As your body recognizes there is too much ultraviolet light, it turns on a defense system.

The immune system, which responds to invaders like viruses and other harmful things like ultraviolet light, kicks in. Some people might see their skin get red or blistered. They might feel itchy or painful. But not everyone experiences sunburn in quite the same way.

A big part of the answer to your question also has to do with human cells. My friend Cynthia Cooper, a researcher at Washington State University, knows a lot about cells and how they work.

She said the human body is made up of billions of cells, and they do all kinds of different jobs. Some cells help us get energy from food, some cells help us grow hair, and other cells in the skin can even make something like a shield that protects us from the Sun’s ultraviolet rays.

These natural shields are what scientists call melanin, a kind of dark pigment. You may remember that pigments are colors we find in nature. Melanin is also part of what gives human beings their skin color.

You can think of the melanin-making cells in your body like a hand with fingers reaching out to the neighbor cells called keratinocytes. The “fingers” of a melanin-making cell can help pass melanin to several keratinocytes at the same time. Then, the keratinocytes can move melanin to the cell’s control center: the nucleus.

This nucleus is really important because it protects your DNA, which contains the instructions your body needs to grow and develop. DNA has all the information that makes you, well, you.

“The melanin almost acts like a little flying-saucer that hovers over the nucleus,” Cooper said. “It reflects the ultraviolet rays to protect the DNA from damage.”

So, if you don’t make a lot of these shield-like flying saucers of melanin pigment, you may be more likely to experience a sunburn. Meanwhile, there are some people who don’t produce any melanin at all. People with this condition called albinism must be very careful in the sun because they don’t have a lot of those natural shields.

In the lab at WSU, Cooper and her team are investigating the innerworkings of cells to learn more about new treatments for people with cell diseases like albinism as well as treatments for the most serious types of skin cancer. When we understand more about how cells work, we can continue help improve human health for everyone.

Speaking of health, one thing you can do to help protect your body and its cells from ultraviolet light is to wear sunscreen when you go outside.

When you wear sunscreen, you can help take care of your body, so your body can keep taking care of you.

Sincerely,
Dr. Universe

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Dr. Universe: How did Saturn’s rings form? -Amelia, 9, Washington State

Dear Amelia,

We still don’t know exactly how the rings around Saturn formed, but scientists who study Saturn’s rings have come up with a couple of ideas.

One common theory many scientists agree upon is that Saturn’s rings are made from the little leftover pieces of what used to be a moon.

My friend David Atkinson is really curious about the solar system and told me more about it. He is a graduate of Washington State University and now works at the NASA Jet Propulsion Laboratory. He also worked on the Cassini-Huygens space research mission which helped us learn more about Saturn, Saturn’s large moon Titan, and the entire Saturn system.

He said that when we investigate questions about Saturn’s rings, it helps to know about both moons and gravity.

Moons are usually smaller than their planets. Our Earth has just one moon, but Saturn has 82 moons. Each moon has a name, such as Titan, Enceladus, Mimas, Dione — just to name a few.

According to NASA, there are likely another 29 moons around Saturn, but we are still waiting to confirm the discoveries and give the moons their names.

Saturn, like Earth and other planets, also has gravity around it. The gravity gets weaker the further away you travel from the planet.

Atkinson said that for each moon, Saturn’s gravity on the side of the moon that faces the planet is stronger than the gravity on the side that faces away from the planet.

“The gravity stretches the moon out a little bit,” he said. We call this a tidal force.

He told me the story about a scientist named Édouard Roche who figured out that if a moon gets close enough to a planet, this stretching force will be so strong that it can break a moon apart.

“The theory is there was a small moon of Saturn that got too close to the planet. That small moon got inside Saturn’s Roche Limit, or inside that special distance, and the tidal force broke the moon into pieces,” Atkinson said. “Those pieces spread themselves around the planet and that is the ring.”

Throughout the years, scientists have been able to study the size, thickness and materials that make up Saturn’s rings. We’ve learned that the rings are made up of rocks, ice and dust. Scientists have also asked what would happen if we took all of the materials that make up Saturn’s rings and packed them together.

“It turns out that it would pack together into a pretty small-size moon,” Atkinson said.

You know, Saturn isn’t the only planet that has ring systems. Jupiter, Uranus and Neptune also have rings, too. But the rings are pretty faint and much harder to see, even with a telescope.

There is still so much to discover about our solar system and the worlds beyond our Earth. Maybe one day you can help us learn more about the way different planets form and help us find answers to big questions just like this one.

Sincerely,
Dr. Universe

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Dr. Universe: How does toothpaste clean your teeth? -Lucy, 10, Pullman, WA

Dear Lucy,

If you are anything like me, every day you squeeze a little toothpaste onto your toothbrush and brush your teeth. Toothpaste gets its cleaning power from a few different ingredients.

My friend Mark Leid was happy to tell us about how they work. Leid spent part of his career teaching future dentists. He is also dean of the Washington State University College of Pharmacy and Pharmaceutical Sciences.

First, he told me the outer covering of a tooth is called enamel. It’s the hardest tissue in the whole human body—even harder than bone—and it helps with things like chewing your food.

Inside your mouth and on your teeth, there are lots of tiny living things called microorganisms. They are so small you’d probably need a microscope to see them, but they like to eat the leftover food bits that get stuck in your teeth.

As they eat those leftover bits, they also make acid. That acid can break down your enamel, which can lead to cavities or tooth decay.

“We can’t make new enamel,” Leid said. “Once our enamel is gone, it’s gone.”

That’s part of the reason it is so important to brush our teeth. When you brush your teeth with toothpaste, it helps get rid of that acid.

Leid said some ingredients that help get rid of the acid and leftover food in your teeth are called abrasives. These create scrubbing power and sometimes give the toothpaste a gritty texture. Abrasives are combinations of atoms, which are like building blocks, that come together to form something called a chemical compound.

One example is calcium carbonate, which is made up of carbon, oxygen and calcium atoms. Another is silica gel, which is made up of silicon and oxygen atoms. Some other compounds create scrubbing power, but these are two of the main ones.

Meanwhile, other toothpaste ingredients help create foaming action, such as sodium lauryl sulfates and sodium N-lauryl sarcosinate. These are the same compounds that give soaps their foamy qualities.

Take a look at the back of your toothpaste tube and see what ingredients you can find. Another ingredient you might notice is fluoride, which helps strengthen your enamel. You might also see other flavoring agents that give toothpaste its taste, like mint.

“Otherwise, it would taste pretty chalky and bitter,” Leid said.

When you brush your teeth, you are helping your mouth stay clean and healthy. In addition to brushing, flossing is also important. Floss helps remove any excess food between your teeth that might invite those acid-making bacteria.

It’s great to hear you are curious about toothpaste, Lucy. Who knows, maybe one day you will be a chemist, a dentist, a pharmacist or anything else you dream. Keep up the great brushing, keep asking great science questions and don’t forget to floss.

Sincerely,
Dr. Universe

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Dr. Universe: How do touch screens work? -Nicholas, 11, Florida

Dear Nicholas,

When I got your question, I decided to do a little experiment. First, I tapped my paw on a tablet and sent a message to a friend. Next, I put on a pair of wool mittens and started typing, but the screen did not respond. Finally, I used a banana to see if I could use it to swipe the screen. It actually worked.

I wondered what exactly was going on here and decided to take our questions to my friend Praveen Sekhar. He’s an associate professor in the Washington State University School of Engineering and Computer Science.

Sekhar told me our touch screen devices use electricity to work and that different materials can impact how the electricity flows. Some materials called insulators keep electricity from flowing, such as the wool mittens. Then there are objects such as your finger or a banana that allow electricity to flow from one place to another. We call these conductors.

When your finger touches the screen, it creates a sort of pathway for electricity to flow from your finger to the device. You read that right: you have electricity in your body— from your toes to your fingers.

Sekhar said you can think of how these touch screens work sort of like a battery. If you look at a battery, you will see it has a positive charge end and a negative charge end. Electricity will start to flow if both ends are connected to your device.

A touch screen device on its own has a negative charge, he said. But once your finger connects with the touch screen it becomes positive. The electrical charges can work together to help your device work. This kind electrical ability is called capacitive technology and is found in many touch screen phones, tablets, and computers.

Sekhar also told me about another kind of touch screen. These are the kinds of touch screens we see at ATMs and in grocery stores. These screens aren’t quite as bright as your computer or phone. We call these resistive screens, and they are made of layers of glass and plastic with a chemical coating and a sheet of metal underneath them.

When you press these screens with your finger, you apply pressure to the material. Inside the material, the electrical charges start moving inside as they respond to pressure from your finger and allow the device to work.

Whether it is capacitive or resistive technology, touch screens have become part of many people’s daily lives.

With help from an adult, perhaps you can do a little investigation into touch screens, too. Collect a few small items from around the house to find out which ones are insulators and which ones are conductors.

Screens are quite fragile so you may want to use materials that will be gentle to your screen, like a cotton swab, an eraser or a banana. Touch the objects to the screen to see if they allow your device to respond. Make a list of which objects conduct, or allow electricity to pass through, and remember how electricity helps your phone do all kinds of amazing things.

Sincerely,
Dr. Universe

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Dr. Universe: Do flying squirrels really fly? – Gwendolyn, 9
 
Dear Gwendolyn,
 
Flying squirrels may not really fly, but they do have flaps of skin on their bodies that act like parachutes and help them glide through the air.
 
My friend Todd Wilson told me all about it. He’s a wildlife biologist with the U.S. Forest Service in Oregon and graduate of Washington State University who researches Pacific Northwest ecosystems and the animals that call them home— including flying squirrels.
  
When flying squirrels are trying to avoid predators, like weasels, sometimes they will run to the top of a tree. The weasel might think the flying squirrel has nowhere else to run. That’s when the flying squirrel makes its move.
 
“The flying squirrel can just take off and glide,” Wilson said. “When they launch themselves from a tree, they can actually go quite a ways out, but they’re not actually flying.” 
 
Depending on the tree, flying squirrels can sometimes glide for hundreds of feet. As they glide, they can use their tail to steer around and between other trees.
 
Flying squirrels are not only amazing to watch, but they also play an important part in forest ecosystems.
 
While other tree squirrels eat a lot of nuts or seeds from tree cones, a big part of a flying squirrel’s diet is something different. They eat an organism called fungi that live under the soil.
 
“Flying squirrels eat the fruits of the fungi in the forest—if the fruit is above ground, it is called a mushroom. If the fruit is below ground, we call it a truffle. Flying squirrels eat a lot of mushrooms and truffles, and then pass them through their digestive system,” Wilson said.
 
Flying squirrels help spread the fungi around the forest through their, well, poop. As new fungi grow, they suck up nutrients from the soil and pass on those nutrients to trees. In exchange, the trees give fungi some sugars that help the fungi grow.   
 
While flying squirrels play a big part in our forests, we rarely see them during the day. They are nocturnal, or active at night. But sometimes we can hear them.
 
They are pretty quiet compared to other squirrels, but they occasionally make a chittering sound as they meet up with other flying squirrels. We sometimes hear a big slap when they land on a tree. After all, there’s a lot of power and speed in that glide. 
 
When flying squirrels glide during the night, they may pass other nocturnal neighbors in the sky, like bats.
 
Of all the thousands of mammal species on our planets, bats are the only mammals that can truly fly.
 
You know, the living things in the forest are linked together in important ways. They need each other to live and grow. Humans also play a big part in our forest ecosystems.
 
Can you think of ways humans are connected to the forest? Maybe you can even find some connections between you and a flying squirrel. Share your answers and ideas with us some time at Dr.Universe@wsu.edu.
 
Sincerely,
Dr. Universe

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Dr. Universe: Why do dogs and cats spin around before they sit down? – Antonio, 10, Richmond, Va.

Dear Antonio,

That’s a great observation about cats and dogs. Even I wasn’t sure why cats spin around before they sit down, so I took your question to my friend Dr. Jessica Bell.

She is a veterinarian at the Washington State University Veterinary Teaching Hospital and has seen quite a few cats and dogs walk in a little circle before they sit down.

“It’s a common thing we observe as veterinarians, but we can’t talk to cats and dogs and ask them ‘why,’” she said. “From a behavioral standpoint, it probably stems back to their wild instinct.”

An instinct is a behavior that animals don’t have to learn. They are born with this behavior, and it often helps them survive in the world.

When cats and dogs spin in a full-circle, they have a chance to observe their environment. They might even spin in circles a few times to be certain the spot where they want to sit is safe.

They are likely keeping their eyes out for any danger, such as predators. This behavior was especially important when felines and canines lived in the wild. While a lot of cats and dogs may live in homes with humans these days, they never lost this instinct.

You may have also noticed that sometimes cats and dogs sniff around as they get ready to lie down. Both senses of sight and smell can help these animals make sure the coast is clear. Bell also told me that once the animal knows a space is safe, it will often return to the same spot.

“They often position themselves in the same place on their bed every time or face the same direction,” she said.

While that may be the more scientific answer to your question, she also offered another idea.

“I think many dogs and cats are just finding a good, comfy, fluffy spot to lay down with just the right depth and cushiness,” she said.

Finding a good place to rest can also be helpful for dogs who are getting a bit older. For instance, dogs that have arthritis, a condition where the joints get stiff or swollen, will often walk in a slow circle before they lie down.

If you keep your eye out, you may notice that other animals, such as horses or birds, walk in a circle before they sit, too. You might see birds getting comfortable in their nests or a birdhouse. They even flip around their feathers and move different parts of their nest to get everything just right before they settle in.

You know, a lot of veterinarians pay close attention to animal behavior and ask a lot of questions about it as they take care of our pets. If you keep up the great observations and continue to ask questions, you might just help us learn more about the amazing animals on our planet one day.

Sincerely,
Dr. Universe

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Dear Dr. Universe: Why do some cheeses stink? – Cody, 11
 
Dear Cody,
 
When you take a whiff of stinky cheese, that smell is coming from one of its very important ingredients: microorganisms. 
 
Microorganisms are so small, you’d need a microscope to see them, but sometimes they give off a big stink. To find out more about stinky cheese, I talked to my friend Minto Michael.
 
Michael is a professor of dairy science at Washington State University and told me microorganisms do a few different jobs to help make cheese. These microorganisms can consist of bacteria, yeasts or molds, but bacteria are the most important in cheesemaking.
 
When cheesemakers add lactic acid bacteria to milk, the bacteria help get the milk ready for another ingredient called rennet, an enzyme. This enzyme helps turn the milk from a liquid state into more of a solid that will become cheese.
 
While the bacteria may do a lot of work to help make the cheese, there are benefits to the job.  
 
“These bacteria eat up the milk sugar, milk proteins and milk fat, so that they can get energy and multiply,” he said.
 
As the bacteria eat to get energy, they can also produce a stinky gas. The gas is made up of molecules. Some of these molecules that include ammonia or sulfur compounds are responsible for the smell in a lot of stinky cheese.  
 
When certain molecules come in contact with receptors in your nose, your brain helps you figure out what you are smelling. Maybe your brain tells you to stay away from stinky cheese—or maybe it makes you want to try it.   
 
Michael told me about some of the most smelly, or pungent, cheeses. One of them is called Roquefort cheese. This is a kind of a blue cheese that gets its odor from a mold named Penicillium roqueforti. If we looked at it under a microscope, we might notice that it is a kind of paint-brush shape. Penicillium in Latin means “painter’s brush.”
 
Meanwhile, a different kind of bacteria called Brevibacterium linens is responsible for the smell and flavor of some other blue cheeses. Brevibacterium linens is not only the bacteria responsible for one of the smelliest cheeses on the planet called Époisses, but is also the same bacteria that makes the smell of human body odor. 
 
When people make cheese, sometimes they will let it age for a while. For some cheeses it may be two months or even two years before they are eaten. As the cheese ages, the aromas often start to get stronger and stronger. Of course, not all microorganisms produce gases that are stinky.
 
One of my favorite non-stinky cheese varieties was developed at Washington State University. It’s a sharp white cheddar called Cougar Gold that comes in a can.
 
After investigating your question, I was curious to find out what kind of bacteria is in this cheese. It turns out the answer is a top-secret recipe even I’ll never know. But it’s no secret that it tastes and smells delicious.
 
Sincerely,
Dr. Universe

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Dr. Universe, How do birds know where to migrate? – Jasmine, 10, Gainesville, Florida 

Dear Jasmine,  

There are all kinds of different birds on our planet, and they migrate to different places.

My friend Heather Watts, a researcher at Washington State University, is really curious about bird migration and told me more about how birds know where to go.  

She said there are some birds that make a round-trip flight when they migrate. For instance, the bar-tailed godwit will make long flights between Alaska and New Zealand, traveling more than 7000 miles without stopping.  

Meanwhile, a blue grouse makes a much shorter round-trip flight. It migrates less than a quarter of a mile.   

Scientists think that some birds may know where to go because of a kind of program that’s built into a bird’s DNA. It’s sort of like being born with a set of directions they know how to use. This genetic information is passed down from bird grandparents to bird parents to the offspring.  

“What we think a lot of birds do the very first time they migrate is use a program that tells them what direction to go and how far to go in that direction,” Watts said. 

On a bird’s first migration, it may also follow other birds. The next migration season, the bird may be able to use clues from the environment to find its destination.   

There’s another kind of migration that has scientists, like Watts, asking lots of big questions. It turns out there are actually birds that do not migrate to the same location every year.  

We might see birds like pine siskins breeding in California one year and then in Canada the next year.

“We don’t know as much about this type of migration,” Watts said. “It’s really hard because we don’t know where the birds are going to be and when they are going to be there.”  

Watts and her lab are studying the pine siskins to learn more about the ways these types of nomadic birds migrate and what might be going on behind that behavior.  

Different birds may migrate in different ways, but they will often migrate for similar reasons. While there are some unsolved mysteries around migration, one thing we do know is that migration is really important for helping birds find what they need to reproduce and survive.  

You know, it can be quite fun to watch all the different birds in our neighborhoods. Here’s a science challenge for you: the next time you go for a walk or gaze out the window, see what birds you can spot. With help from a grown-up, see if you can find the name of the bird online or at the library. Finally, do a little research to find out how it migrates and discover the journey your bird takes.  

Sincerely, 
Dr. Universe

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Dr. Universe: Why do mushrooms grow in rings? We have a lot of giant ones in our yard right now! – Layne, 8, Spokane 
 
Dear Layne,
 
When you see a ring of mushrooms, it’s likely they are exploring for food under the ground.    
 
Giant mushrooms in your backyard are not animals or plants. They are part of another class of living organisms called fungi. But like you and me, they do need food to survive.
 
That’s what I found out from my friend David Wheeler, an assistant professor at Washington State University, who knows a lot about fungi.
 
He said the mushrooms are just one part of fungi. The other part that explores the soil for food actually lives under the soil.
 
This part is called the mycelium and looks a bit like cobwebs or stretched out cotton candy.
 
Mycelium help the fungi explore different spaces and absorb nutrients from things like dead logs or decaying leaves.
 
Wheeler said we might think about the way a mushroom ring forms, including how the mycelium spreads out, as if it were a ripple in a pond.
 
Just as ripple starts with a raindrop or stone, a mushroom ring begins with a tiny spore.
 
To help grow new fungi, mushrooms will release spores, which are sort of like seeds. After a mushroom releases the spores, they float through the air and when they land in soil, the mycelium begins to grow beneath it.
 
It starts expanding outward from the place where the spore landed. This allows the fungi to cover a lot of ground on the hunt for food.
 
It’s at the outer edge of the mycelium where we see the ring of mushrooms grow up from the soil.  
 
I found out there are some mushroom rings that have been around for a really long time. For instance, one mushroom ring in France has been around almost 700 years.
 
As the fungi spread out in search of food, the ring got wider and wider. Now, the ring is almost a half mile wide. You would have to walk the length of eight football fields to get from one side to the other.
 
Even though fungi don’t have legs, they sure know how to go the distance. And a big part of that has to do with their mycelium.
 
“Every step you take in the forest, under one foot—even one kid foot—there could be lots of cells of mycelium,” Wheeler said.
 
Wheeler also told me that fungi sometimes compete for food. If you look at the mushroom ring in your backyard, you may notice something unusual about the grass around it.
 
Sometimes grass inside the ring may be brown, and the grass inside the ring might be bright green. That’s because fungi and grass both like to eat the same thing.
 
They are both after the nutrients in the soil. But as the fungi grow, they can steal nutrients away faster than the grass can handle. 
 
You know, it’s great to hear you are observing nature in your own backyard. It’s a good reminder that we can find science questions almost anywhere in this big, wide world—even in a ring of mushrooms.
 
Sincerely,
Dr. Universe

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Dr. Universe: Why do mirrors fog up when you breathe on them? -Zinnia, 7, Richmond, Virginia 

Dear Zinnia,

That’s a great observation. When you breathe out, you let a couple of different things into the air.

Not only do you breathe out carbon dioxide, but you also breathe out teeny tiny droplets of water. These water droplets are so small we can’t see them with our eyes.

Scientists actually have a name for these little droplets of water in the air: water vapor. You may remember from our question about the states of matter that there are all kinds of different gases, liquids and solids in our world. Water vapor is a kind of gas.

My friend Cigdem Capan, a physics instructor at Washington State University, said one big factor that can help water move between these different states of matter is temperature.

When you breathe on a mirror, you are helping water move from a gas state to a liquid state. The surface of the mirror is a lot colder than the water vapor that comes from your warm human body. If you breathe on a mirror, you can easily feel that heat releasing into the air.

As water vapor in your breath reaches the mirror’s cool surface, the vapor droplets come together to form a liquid. When this happens, you can see thousands of super tiny liquid droplets form on the mirror: the fog.

Scientists also call this transition from a gas to a liquid, condensation. It’s the same process that helps form big, fluffy clouds in the sky, tiny drops of morning dew, or the water droplets on the outside of your cool water glass.

“If you are wearing eyeglasses and you are wearing a face mask, you can also see the glass fog up,” Capan said.

That’s condensation, too. While you may not always be able to see the water vapor from your breath, when the temperatures drop it is a bit easier to observe this condensation in action.

It’s been pretty cold here in the Northwest, so I’ve noticed this happen when I go outdoors. As we breathe into the chilly air, the warm water vapor condenses into tiny droplets of liquid water—and even some solid water, or ice—that form a kind of miniature cloud. It’s pretty fun to watch.

Whether you fog up the cool air, a window or your glasses, you may have also noticed that the moisture doesn’t stick around forever.

Try breathing on the surface of a glass mirror or windowpane and watch what happens. Eventually, the liquid droplets disappear from the mirror. Why do you think that might be?

Share your ideas with your friends or family, and see if you can work together to figure out where those water droplets go. If you need a hint, do a little bit of research on how puddles dry up or investigate the water cycle on our planet. Tell us what you discover at Dr.Universe@wsu.edu

Sincerely,
Dr. Universe

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Dr. Universe: Can a shadow make a shadow? – Aven, 7, Palouse, WA

Dear Aven,

When we look around our world, we can find all kinds of shadows. One way we can explore the answer to your shadow question is with a little experiment.

My friend Anya Rasmussen, a physics professor at Washington State University, told me all about it.

First, you will need to cast your shadow on a wall. Rasmussen reminded me shadows form when an object—such as your body— blocks light and keeps the rays from reaching a surface—like a wall.

To see how this works, you can ask a grown-up or friend to shine a flashlight or a lamp behind you and onto the wall.

You can also take some time to see how the shape and length of your shadow change as you move closer or farther from the wall.

“If you want to see if your shadow casts shadows, now shine a light on your shadow,” Rasmussen said.

Point another flashlight at the shadow, then take a few moments to observe what happens. Alright, it’s almost time to reveal the answer, so if you want to experiment, come back and finish reading this after you try it out.

If you have continued reading, here is a spoiler alert: A shadow can’t make a shadow. Unlike you and me, a shadow cannot reflect or absorb light. It can’t block rays of light and keep that light from reaching a surface.

While you’ve got your flashlight out, there are a few other ways you can play with light and shadows, Rasmussen said.

Perhaps you’ve noticed that sometimes two shadows will come from one object. If you have two flashlights or two light sources, you could try to create multiple shadows by shining the light on an object from two different angles. Maybe you can even see what happens when you use three flashlights.

If you are anything like me, you might also be surprised to learn not all shadows are black. Rasmussen said that if we experimented with red, blue and green lightbulbs we could make shadows in different colors.

We can make small shadows or big shadows. Even our enormous Earth makes a shadow. As the moon passes through Earth’s shadow, it creates a lunar eclipse.

Light and shadows are not only an important part of understanding physics, but they are also a big part of creating art and telling stories, Rasmussen said.

When we look at paintings from impressionist artists like Claude Monet and Edouard Manet, we can see how they paid a lot of attention to these two important elements. After all, shadows and light go hand in hand.

After you’ve finished experimenting, see how many shadows you can spot around your home or around the neighborhood. Perhaps you can even sketch a few different shadowy shapes out on a piece of paper.

Who knows, maybe one day you’ll be a scientist or an artist—maybe you’ll even be both. You are well on your way.

Sincerely,
Dr. Universe

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Dr. Universe: Why does oil on the street look like a rainbow? -Jorgos, 10, Bothell, WA

Dear Jorgos,

When it rains, sometimes we can see oil on the street rise to the top of puddles and spread out into a rainbow of colors.

One of the main reasons we see color is because of light, said my friend Cigdem Capan, a physics instructor at Washington State University.

She reminded me that when our eyes sense colors, we can trace those colors back to different wavelengths of light. Perhaps you can make some waves in the air with your hand. Make small, tight waves. Now make a big, wide waves.

The light waves that help us see color are a lot smaller than any wave we can make with our hand. According to our friends at the National Oceanic and Atmospheric Administration, blue or violet wavelength is about 125 times smaller than the width of a human hair.

When these light waves reflect, or bounce, off different surfaces such as an oily puddle, our eyes and brain work together to help translate the information into color.

It turns out there are two places in an oily puddle where the light waves can bounce off or reflect. If you’ve ever mixed oil and water together, you know that they like to be in separate layers.

One place where the light reflects is the top of the puddle where the air meets the oil. The other place is where oil and water meet. Lightwaves have to travel a bit farther through the puddle to reflect where the oil and water meet.

Let’s say you see some purple spots in an oily puddle. You see this color because red, orange, yellow, green, and blue waves reflect off the puddle and overlap with each other in the air. When the waves overlap, they actually cancel each other out, so you can’t see them with your eyes.

But the violet waves reflect off the surface and travel in unison through the air to your eyes. As they travel, these violet wavelengths get a bit of a boost from each other, and the purple appears bright to your eyes.

The differences in the thickness of the oil can make some wavelengths reflect in unison and that is how we see not just the purple spots, but all the different colors in an oily puddle.

The colors that you see in an oily puddle are also a kind of phenomenon we call iridescence. We can see this phenomenon when we observe the outside of soap bubbles or the colorful feathers of the male peacock.

There are so many different colors in our world. Perhaps you even have a favorite one. A couple of my favorite colors are crimson and gray. No matter what colors we see in our world, remember that we can trace all of them back to waves of light.

Sincerely,
Dr. Universe

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Dr. Universe: How many black holes are in the galaxy and the universe?
-Krisha, 9, New Jersey

Dear Krisha,

While we can’t see black holes with our eyes, astronomers have figured out how to spot these objects in our universe.

One astronomer who is really curious about understanding black holes is my friend Sukanta Bose, a researcher at Washington State University.

First, he told me there are different kinds of black holes. Supermassive black holes can be millions to billions of times the mass of the Sun. We have a supermassive black hole in our own Milky Way galaxy called Sagittarius A*, which is pronounced as Sagittarius A-star.

Scientists think supermassive black holes may be found in the center of most large galaxies.

If you are anything like me, you might be wondering: why not just count all the different galaxies to find the number of black holes?

“Of course, we cannot see every galaxy,” Bose said. “We see many galaxies that are closer because they are brighter.”

For galaxies that are farther away, you have to use very powerful telescopes, he adds.

That also means we have to make an inference about the number of galaxies in the universe. An inference is an educated guess based on evidence and current knowledge about how things work.

Using telescopes, math and their inference skills, astronomers estimate there are hundreds of billions of galaxies and likely hundreds of billions of supermassive black holes— that’s just in the observable universe.

Bose told me there’s another kind of black hole that sometimes forms when a star dies and collapses in on itself. We call these stellar mass black holes.

The Sun is a star, but it is far too small to become a black hole. Only heavier stars make black holes. When it comes to stellar mass black holes, astronomers estimate there are ten million to a billion right here in the Milky Way galaxy.

On the hunt for these massive objects, scientists often look for different interactions among stars or gases, clues that there may be a black hole in the neighborhood.

For instance, when a black hole and a companion star are in a tight orbit, their interaction can sometimes create high energy light we can’t see, but that scientists can detect with their high-tech tools.

“When you open a new way of probing the universe, you see objects that challenge your previous wisdom or theories,” Bose said.

Bose and fellow researchers have been able to spot black holes because of a new way to detect something called gravitational waves. When two black holes collide, they can create a kind of wave that brings information to Earth about its source and helps us learn more about the universe.

It’s a bit like listening for sound waves from particular instruments in an orchestra, Bose said. But instead of picking out the sound of a cello or a flute, they are listening for gravitational waves from those colliding black holes.

Who knows, maybe one day you can help us learn more about black holes and discover ways to help astronomers count them all.

Sincerely,
Dr. Universe

Thanks to all our kid readers who voted for this question in our recent poll. Stay tuned for future polls at askDrUniverse.wsu.edu.

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Dr. Universe: Why do we get tears when we yawn? – Ella, 8, Australia

Dear Ella,

You’re right, a lot of people get tears when they yawn. When you yawn, you actually use lot of muscles in your face. Maybe you can feel the stretch in your jaw, cheeks and eyes.

As the muscles in your face contract, they can put a lot of pressure on the plumbing system that is in charge of making your tears.

That’s what I found out from my friend Karin Biggs, an adjunct professor at Washington State University who teaches anatomy.

She told me that we have two little almond-shaped structures called the tear glands, or the lachrimal glands, that produce our tears. These glands are located up near the eyelids, and it is likely they are making tears at this very moment.

“Tears are made all the time,” Biggs said. “They are responsible for keeping our eyes moist, helping us see and keeping our eyes healthy.”

Meanwhile, there are also two tiny tubes located near the inside corner of your eyes. These tubes, or lachrimal canals, are where the tears can exit your eyes as you yawn.

Like a very slow faucet, the teary fluid is constantly being released from the gland. Gravity pulls the fluid down and around the eye. You might think of it like putting a ball in your bathroom sink then running the water faucet over it. The faucet is your gland, the drain is where tears exit and the ball is the eye.

“When we yawn we are contracting all the muscles in our face,” Biggs said. “We are just squeezing the tears out of the gland and out of the tubes because we have squeezed all of our face at once.”

Biggs also told me there are 43 muscles in the human face. You may squish up a lot of those face muscles when you sneeze or laugh, too.

The muscles in our bodies can help us do all kinds of things. Biggs told me there are even some muscles people have that other people seem to be missing. The plantaris muscle in the knee is one of them. Only about ten percent of people do not have this muscle, but they usually seem to be fine without it.

But tear ducts and tear glands in our eyes are among the many body parts that humans have in common. This plumbing system helps you create, transport and drain all your tears.

The ability to make tears is all a part of the human experience. But other animals like cats and elephants can make tears, too. Tears are mostly water with some other ingredients that help keep our eyes in good shape.

Whether your tears come from crying, sneezing, laughing or yawning, they are often a good sign your body is taking care of you and that your eyes are working well.

Sincerely,
Dr. Universe

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Dr. Universe: When frost freezes, it makes shapes like flowers and ferns. Why does it look like that? – Grace, 13, in Calgary

Dear Grace,

You’re right: frost can sometimes form patterns that look like the ferns or flowers we find in nature.

Those frosty shapes we see on the surface of windows start out as water in the air, said my friend Kai Carter. Carter is a meteorologist with Washington State University’s AgWeatherNet team.

If you’ve ever had a glass of ice water, you may have noticed droplets formed on the outside of the glass. The droplets actually came from water in the air. This water condensed from the air onto the surface of your cup, which means it turned from a gas to a liquid.

This is similar to what’s happening when dew forms on grass. But frost is a little bit different, Carter said.

When frost forms, conditions have to be just right. As water from the air lands on a really cold surface like a windowpane, the water molecules freeze and join together with other water molecules to form patterns of ice crystals.

An ice crystal is made up of two building blocks: hydrogen and oxygen. These hydrogen and oxygen atoms form a hexagon shape that is a kind of six-sided ring. Even though we may not be able to see them with our eyes, these hexagon shapes can repeat in a pattern across the frosty surface of the window.

Sometimes the water molecules can form into one big sheet of frost. But sometimes things can get in the way of the water molecules. They may have to take a new path as they freeze to the surface of the glass.

If the molecules run into something like a speck of dust, salt or even a bit of washer fluid from a car window, they may change their direction. As you’ve observed, they can start to branch out into shapes that might look to us like feathers or ferns or tree limbs.

In mathematics, we call this kind of thing a fractal design. A fractal pattern repeats itself at different scales. One other place you can also find fractal patterns in ferns. The fern frond looks like it’s made up of little fern fronds which look like they are made up of even smaller fern fronds. Next time you see some frost take time to observe its detailed patterns with a magnifying glass.

Even if you don’t live someplace where it gets really cold, you can actually make your own frost right in the kitchen. All you need is a tin can, salt and ice. Fill the tin with ice and 4 tablespoons of salt and mix it up for a minute. Wait a few minutes and see what forms on the outside of the tin.

The salt is important because it melts the ice, while at the same time helping the mixture drop below freezing. Why do you think that might be? What happens when you add more salt or more ice? Tell us about your frosty experiments sometime at Dr.Universe@wsu.edu.

Sincerely,
Dr. Universe

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Dr. Universe: Why does water in ponds not get soaked up by the dirt at the bottom? – Rocky, 11, California

Dear Rocky,

That’s a great observation. If we investigated the bottom of a pond, we might find a few different things. Besides a few fishes and frogs swimming around, we might observe mud, algae, rocks and soil at the bottom.

My friend Joan Wu, a hydrologist at Washington State University, is really curious about the water on our planet. She told me a few different earth materials help keep pond water from seeping down into the ground.

Let’s imagine we filled a jar with one of these earth materials: rocks. Inside the jar, we would see some gaps between the rocks. If we poured water into the jar, the water will be able to move into those empty spaces. But now let’s say we had a jar of rocks, and we poured in some sand.

This time, the grains of sand would fill spaces between the rocks. Next, we could add particles of earth called silt that are so small they could fill in any spaces between the grains of sand.

Finally, we could add some even smaller particles of clay. In the jar—or the bottom of a pond— these materials are packed together. The material isn’t very permeable, which means it can keep the liquid from passing through it.

“Over a long, long time, the bottom of the pond itself evolves and changes,” Wu said. “The materials settle and the little particles, or sediments, fill in the large pores.”

As water, wind, gravity and even animals break down rocks, the rocks become smaller and smaller particles that sink to the bottom of the water. When water runs across the Earth’s surface during a storm or as snow melts, these fine materials can also end up in a pond.

For the most part, these materials keep the pond from losing too much water, but sometimes a little does escape into the ground. Meanwhile, a little water can also escape into the air.

“Eventually, you will lose water from the top and from the bottom of a pond,” Wu said.

We lose the water from the top of a pond because of something called evaporation. You may know about evaporation if you’ve ever seen a puddle on a sidewalk that was there one day and gone the next.

When the sun heats up the surface of water, the water can turn from a liquid into teeny tiny drops called vapor. The vapor rises up into the atmosphere where it can eventually become clouds. Those clouds help produce rain and snow that fall back into lakes, rivers and ponds.

When we take the time to look, we can find a lot of connections between our atmosphere, water and earth. These systems shape many habitats for life on our planet.

The next time you visit a pond, see what kinds of living things call it home. Who knows, maybe one day you’ll be a scientist who can help us learn more about the world of water.

Sincerely,
Dr. Universe

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Dr. Universe: Why do trees have sap? -Aliyah, 8, Kirkland, WA

Dear Aliyah,

Just as blood moves important stuff around the human body, sugary sap moves important things around a tree.

My friend Nadia Valverdi told me all about it. She’s a researcher at Washington State University who studies how apple and cherry trees survive in different environments.

When we eat food, like a delicious apple or a handful of cherries, we get important nutrients.

Along with some help from the digestive system, our blood helps carry nutrients to different parts of the body to keep us strong.

Trees need nutrients, too. They use their roots to suck up nutrients and water from soil. They also have the ability to make their own food: sugars.

Trees absorb sunlight through their leaves and can use this energy from the sun to make sugars from water, carbon dioxide gas from the air and a few other ingredients.

A lot of sugars are made in the leaves, but they don’t do the tree much good if they just stay in one spot. The sugars have to get to other parts of the tree to help it survive. That’s where the sap comes in.

“Its main task is to make sure that every organ is well-fed and growing,” Valverdi said.

While our blood moves through tube-like veins and arteries, sap flows through two different tube-like parts of the tree.

One part, called xylem, moves important stuff like water and nutrients from the bottom of the tree to the top—from its roots to its leaves.

The other part, called phloem, moves important stuff from the leaves to other parts of the tree, such as the branches, roots and fruit.

I asked Valverdi how a sticky, gooey liquid like sap could move through these tubes. After all, sap doesn’t seem to move on its own.

It turns out that some liquids, such as sap, can move through a narrow space without any help from gravity or other outside forces.

This can happen in plants or trees when sap escapes through tiny, microscopic holes in the leaves. When sap molecules escape the leaf, more sap molecules move in to fill the empty space and keep the sap flowing upwards through the tree.

It’s a phenomenon we find happening everywhere from house plants to big apple trees to celery stalks.

“All trees and plants have sap,” Valverdi said. “The difference is that sometimes in big trees, we can see it with our eyes because it is more gooey.”

One really gooey kind of sap you might have seen before comes from sugar maple trees. You may even put it on your pancakes or waffles. You guessed it, maple syrup is a kind of sap.

Just like us, trees have systems that help them move important stuff around. These systems help the plants survive. When trees do well, that’s good for us, too. They do so many things for us from making the oxygen we all breathe to giving us delicious fruit to eat.

Sincerely,
Dr. Universe

You can learn more about the xylem and phloem in this simple activity using food coloring, water and some celery. https://www.youtube.com/watch?v=KIug9Foou3s

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Dr. Universe: How do people stain glass to make it all the colors it can be? – Emily, 10, Edmonds, WA

Dear Emily,

Ever since humans discovered they could use sand to make glass, they’ve been experimenting with it. They even learned how to control the colors.

My friend Dustin Regul is a stained glass artist and painter who teaches fine arts at Washington State University. He told me more about where glass gets its color.

“It’s actually metals that help change the color of the glass,” he said.

We can add these metals to glass in the form of a compound. A compound is a combination of one or more elements. For example, table salt is a compound made up of the elements sodium and chloride.

Yellow glass can be made using a compound called cadmium sulfide. Red glass can come from adding gold chloride. Manganese dioxide can make glass purple. Blue glass comes from adding the compound cobalt oxide.

Glassmakers add in compounds when they melt the sand. The temperature has to be just right for everything to work. They heat the sand to about 3,000 degrees Fahrenheit—that’s even hotter than lava. As the melted sand cools, it becomes glass.

It turns out, glass made from melted sand doesn’t always instantly become transparent. The glass sometimes has its own natural color.

“You can imagine really old glass bottles,” Regul said. “They kind of have that bluish or greenish tinge.”

Glassmakers also figured out that a compound called sodium nitrate could help clear up the glass.

Regul said glass is a pretty unusual material. It’s not a solid or a liquid. Scientists call it an amorphous solid, which means a state somewhere in the middle of those two states of matter. It’s also a very fragile material.

Regul must be very careful when he works on stained glass projects. Before he gets started, he makes a plan and draws out his design on paper.

Next, he cuts up the paper drawing into pieces. It’s a guide that will help him as he cuts pieces of glass into shapes with a special glass cutting tool. Finally, he uses copper tape to connect the pieces together and applies heat to seal it all up.

In medieval times, when stained glass first became really popular, people used a different technique. The glass pieces were held together with long strips of a bendy material made of lead. On each side of the lead strip was a little channel where the edge of glass could be tucked in. And like the technique Regul uses, adding heat to the strip helped keep the glass in place.

Humans can use these really small pieces of glass—in all sorts of colors—to form a bigger picture or story. Whether you are in the lab or the studio, it’s amazing what you can create and discover when you set your mind to it.

Sincerely,
Dr. Universe

P.S. Be sure to check out the Ask Dr. Universe podcast on Spotify, iTunes, or at https://askdruniverse.buzzsprout.com/.

~

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Dr. Universe: Along with many others, we are at home during the coronavirus pandemic and Layla (5 1/2) has been learning new exercises to stay healthy. Layla would like to ask: WHY and HOW does exercise help our bodies? She would also like to know what the best exercise is for our bodies. 

Dear Layla,

When we exercise, it helps the body and mind in so many different ways.

One important muscle that benefits from exercise is the heart. Maybe you’ve felt your heart beat harder and faster when you run or climb at the playground.

As the heart gets stronger, it also gets better at pumping blood around the body. That’s really important because your blood is full of oxygen you need to help fuel all your body’s systems.

That’s what I found out from my friend Chris Connolly, an associate professor at Washington State University who knows a lot about the science of exercise.

“Exercise is good for the systems inside your body. Your heart, your lungs and your digestive system,” Connolly said. “It’s also really good for your mind.”

When you are active, you are improving your memory, creativity and even critical thinking skills.

Many studies have found that kids who exercise before a test get better scores. Tests can be stressful, but exercising can help reduce all kinds of nervousness. It’s a great way to help us calm down.

>From the heart to the mind, exercise is one way we can care for our bodies. And with so many different kinds of exercises to try, I just had to find out which one was best.

“The best exercise we can do is the one we are going to do consistently the rest of our lives,” Connolly said.

He reminded me humans have different abilities and interests, so how we exercise will look a little different for each person. Find the exercise that’s just right for you and stick with it.

Connolly likes to lift weights and go running. He and his family sometimes build obstacle courses in their yard, too. I don’t know about you, but I think that sounds like a fun way to help stay fit. As for me, I like to explore the outdoors, stretch and climb trees.

Like you, I enjoy trying out new ways of exercising. The question you asked inspired me to try these different exercises that had me hopping like a frog, crawling like a crab, waddling like a duck and stretching out my arms and legs like a starfish. Maybe you can try them, too.

It turns out people need different amounts of exercise as they get older. A lot of kids ages three to five get all the exercise they need just from playing. For kids who are older than five, an hour of physical activity a day can help strengthen bones and build muscle. Meanwhile, adults need about 150 minutes of exercise a week.

It’s important to stay active throughout our entire life, so it’s good to hear you are learning some new exercises. You’re off to a great start. Next time you do your favorite exercises, think about all the wonderful things you are doing for your body and all the things your body does for you.

Sincerely,
Dr. Universe

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Dr. Universe: Why does the internet go down? -Mia, 11, Sheridan, Wyoming

Dear Mia,

The internet has helped many people connect with classmates, friends and family during the pandemic. But you’re right, sometimes the connection gets lost.

My friend Dingwen Tao, an assistant professor of computer science at Washington State University, said we can think about the internet like a highway of information.

You may remember from our question about how the internet works that information, like the data that makes up your favorite cat video or science website, travels through electronic signals we cannot see with our eyes.

Tao said these electrical signals can also move through a system of underground wires and cables. The cables and wires run from where you are using the internet to a local internet office to a regional internet office.

One reason the internet might go down is that there is a broken link between these locations. Or these links might get overloaded with information.

“You and your neighbors can share the same link connected to the central office,” Tao said. “It’s like people are sharing the same road, but sometimes if too many people are using the same road, there will be a lot of traffic.”

When there is more information than the links—like those cables or the electrical signals— can handle, then the internet might go down.

Tao said there are few other things that can get in the way of electrical signals.

For example, even a thick wall can block Wi-Fi signals that carry information delivering, say, your favorite podcast. If you are in one room and the router—a device that picks up signals and pushes them to their destination—is in another room, you may lose the signal.

Nature can also play a part in making your internet go down, said Tao. A tree may fall down and knock out some wires during a big storm, or a fire may cause damage to cables.

The disaster could even be hundreds of miles away from you and closer to the regional internet office. But because you are connected to the central office, you and your neighbors might still lose your internet service.

The connections we can make online are important, so many people around the world are helping bring internet to places that don’t have internet access or where the internet is really slow.

Here in Washington, some of my friends at the university are working on a project to help people across the state get access to the internet, including in rural places. The work is helping students get the technology they need to go to school online, so they can keep learning.

As you learn more in school, you may discover more about the innerworkings of the internet. Whenever the internet goes down, there are people who use their deep knowledge of the technology and great problem-solving skills to help us figure out what might be wrong.

They help us get back on the information highway, so we can stay connected—even when we are stuck at home.

Sincerely,
Dr. Universe

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Dr. Universe: Why do we get pins and needles when we don’t move for a long time? -Jocelyn, 9

Dear Jocelyn,

If you’ve ever had a leg or an arm “fall asleep,” the nerves in your brain and body were sending you an important message.

That’s what I found out from my friend Darrell Jackson, a researcher at Washington State University who studies how drugs affect the nervous system.

The nervous system is made up of bundles of nerve fibers that help humans think, feel and navigate the world. These nerves also help people sense things like temperature, vibrations, pressure and pain.

Jackson said you may feel pins and needles when your nerves get too compressed or squished down. We call this experience paresthesia (pear-ES-theesha).

It takes something called mechanical energy to compress the nerves. This energy might be the pressure from your head resting against your hand during a nap or the pressure on your legs while sitting crisscross applesauce.

When the nerves feel this pressure, they activate a kind of electrical energy. That’s right, you are full of electricity. The body and brain use electrical signals to send information to each other.

The nerves in your tingling leg, arm, foot or hand, can send information along your spinal cord which stretches from the lower back to the brainstem.

“From there, you are relaying the message from the spinal cord to an area of the brain called the diencephalon,” Jackson said.

The message continues on to a section of your brain called the somatosensory cortex. It’s here that you actually become aware, or perceive, that your leg is tingling or that your hand feels like it’s full of sand.

“Once you get up and you start moving around, you’ll get information immediately,” Jackson said.

All of this information moves through the brain and body really fast—about 11,679 feet per second. That’s like running nine laps around a standard running track in a single second.

When the body senses this tingling pain, it activates another pathway in the body. The brainstem helps send information back down to the spinal cord to make the body less painful and less tingly.

If you compress your nerves for too long, it can damage your ability to sense the world. The pins-and-needles feeling can be a useful strategy to protect your nerves and keep you healthy.

Our nerves are really important, and there are more than 7 trillion in the human body. Jackson reminded me our nerves not only help us sense pain but also play a big role in the reason why we have memories.

Jackson said one unsolved mystery about the brain is exactly how humans store their memories. Scientists are still really curious about it. But that’s a question for another time.

The next time you experience paresthesia, maybe you will remember something you learned from investigating this very question. Maybe you will take a moment to remember all the amazing things your body and brain do for you each day.

Sincerely,
Dr. Universe

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Dr. Universe: How do you make cider? -Julianna, 7

Dear Julianna,

We can make cider with juice from apples. There are many different kinds of apples and a few different ways to squeeze out the juice.

My friend Bri Ewing Valliere told me all about it. She’s a food scientist at Washington State University who knows a lot about cider.

The first step is to pick out the apples. Honeycrisp apples will make a sweet cider. Granny Smiths are more acidic and will make a tart cider.

“We could make a single batch of one kind, or we could mix different kinds of apples together and see how it turns out,” she said. “No matter what, it’s going to taste good.”

It’s important to wash the apples to remove any dirt or bacteria. Next, it’s time to squeeze out the juice.

“It’s not like oranges or grapes where you can just squeeze them and the juice comes out,” Valliere said. “We need to get the apples into smaller pieces.”

After a grown-up helps cut the apples into quarters, the slices can go into a juice press. One kind of press is a basket press, which is like a small barrel with a device to grind up apples.

There’s also a wooden plate that goes inside the barrel on top of the ground-up apples. As we push down on the wooden plate, the force squeezes out the juice from the fruit.

The juice flows out the bottom of the press, which works a bit like a pasta strainer. It separates the apple solids from the liquids. As the juice flows from the press, we can catch it in a jug or bucket.

Valliere said another kind of press is called a bladder press, which has a balloon-like device that pushes against the fruit to squeeze out the juice.

While you may not have a basket or bladder press at home, with the help of a grown-up you can find a recipe online that uses similar steps: use small pieces of fruit, press the fruit to make some juice, and pasteurize it.

When we pasteurize the juice, it helps kill any harmful bacteria that could possibly make us sick. All we have to do is heat up the juice up to at least 160 degrees Fahrenheit. Finally, it’s time to enjoy the cider.

While some cider comes from small farms or our kitchens, there are also machines in factories that produce thousands of gallons of juice.

Valliere told me that juice processors sometimes will add something called enzymes to the pressed juice. The enzymes help turn the light brown, cloudy cider-looking juice into the clear, golden liquid we know as apple juice.

A big part of the reason we have apple juice and apple cider is also because of the hardworking farmers and farmworkers who take care of our apple orchards—and we have a lot of orchards here in Washington State.

The next time you take a sip of cider, think of all the people who helped make it and all the science in your cup.

Sincerely,
Dr. Universe

Are you curious to learn more about how basket presses work? Check out this video from the Cedar Creek Grist Mill. This historical mill in Woodland, Washington is listed on the National Register of Historic Places.
https://www.youtube.com/watch?v=SXTH6uhDAGQ&feature=emb_title&ab_channel=ClarkCountyToday

~

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Dr. Universe: How are gummies made? -Hayden, 11, Webb City, MO

Dear Hayden,

Gummies can come in all different shapes and flavors. Maybe you’ve had gummy worms, gummy bears, or peach rings.

It turns out that gummies require just a few simple ingredients. That’s what I found out from my friend Connie Remsberg, a pharmacist at Washington State University.

She said making gummies requires a little gelatin, water, a mold, and some help from a grown-up.

If you want to make gummies at home, you can warm up about ½ c. of water on the stove. Add a 3 oz. package of flavored gelatin (which contains sugar). Then add one tablespoon of unflavored gelatin.

Mix it all together until it is dissolved and ready to come off the stovetop. It’s very important to ask a grown up for help and to be super careful when working around hot surfaces. A good scientist—or gummy maker—always puts safety first.

The gelatin is a made up of things called proteins and peptides. They come from animal bones or cartilage. When you dissolve gelatin in water, the tiny proteins act kind of like spaghetti and get all tangled up together. Between the tangles, there is space to hold sugar and water.

Next, you will need something to shape your gummies. A silicone mold is handy because it won’t melt when you pour in the warm mixture. Some stores sell molds with shapes like little bears built right in. Be sure to spray the silicone mold with nonstick cooking spray before filling in the shapes.

If you don’t have a silicone mold, you can spray the bottom of a metal pan and pour the mix into a thin layer. Later, you can use cookie cutters to cut different shapes from the gummy slab. If you have some extra plastic straws laying around, you can follow these instructions to make gummy worms.

After you have your mix in the mold, put it in the fridge until the gummies form. Oh, and if you want to make a vegan version of gummies, you might use agar agar powder, which comes from seaweed and works as an alternative to gelatin.

Remsberg is very curious about compounding—or how pharmacists can combine different ingredients together to create a medication that’s just right for a patient.

She told me that sometimes pharmacists will create gummies that contain a person’s medicine to make it easier to take. Gummy vitamins are just one example. The body needs 13 different vitamins so some people will take a vitamin gummy in addition to eating fruits and vegetables.

One other fun way to experiment with gummy bears—even the kind you buy from the store—is to soak them in different liquids, or solutions, such as water, saltwater, vinegar, or bubbly soda water. Let them sit for a few hours, or overnight, and observe what happens.

Do they shrink? Get bigger? Explode? Okay, spoiler alert, they won’t explode. But tell us what you discover and why you think it all happened at Dr.Universe@wsu.edu.

Sincerely,
Dr. Universe

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Dear Dr. Universe: Why do garden spiders hang upside down in the middle of their webs? -Abree, 10, New Jersey

Dear Abree,

That’s a great observation. Garden spiders and other orb-weaver spiders crawl all around their webs, but we often see their heads pointing down toward the ground.

My friend Todd Murray, an entomologist at Washington State University, told me about a group of scientists that had a question a lot like the one you’ve asked.

These scientists used mathematical models to learn about orb-weaver spiders and how they move around the web. They discovered spiders that wait with their head down for prey can reach prey faster than spiders that wait with head up for their prey.

While there are exceptions, this position gives spiders an advantage when getting food. Sometimes prey will hit the top of the web, but end up tumbling to the bottom of the web. A spider higher up on the web with its head facing down would be able to see prey below. Gravity also helps spiders as they run down the web.

Murray reminded me how different kinds of spiders can make different webs. Orb weavers tend to make webs in circle shapes. These spiders have parts called spinnerets located in their rear ends, or abdomens, that produce the silk.

Some orb-weavers may create a trap line with their silk, which attaches them to the middle of the web. When an insect hits the web, the trap line vibrates and the spider can sense dinner has arrived. It might just be a fly, mosquito, moth or wasp.

As fall gets underway, orb weavers eat lots of insects and get bigger. You may identify an orb weaver from its brick red to orange body with white splotches. We see quite a few orb weavers in Western Washington at this time of year. You may notice more spiders and webs in your neighborhood, too.

We are still learning exactly why some spiders build certain kinds of webs. Murray said a wasp in Costa Rica has even revealed how a spider’s web designs can get hacked. The wasp glues an egg on the spider’s abdomen. When the egg hatches, the little larva attaches to the abdomen and starts living off the spider.

“That grub sits there and steals the nutrients from the spider like a vampire does, or a tick, or other blood-sucking creature,” Murray said. “As that grub grows on the spider, the spider does a really amazing thing.”

On the last night of its life, the spider start builds a totally new kind of web that looks a bit like a hammock. Once the hammock is made, the spider puts the larvae into the hammock.

“It really does show you how those web-building abilities are hard-wired in the spiders, but that they can be manipulated,” he said.

If you keep asking great questions like scientists do, maybe you’ll help us learn even more about the world of arachnids. In the meantime, keep an eye out for the spiders’ beautiful webs.

Sincerely,
Dr. Universe

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Dr. Universe: Why do ants build mounds? – Isabelle, 4, Eagan, MN

Dear Isabelle,

Ants build mounds in all shapes and sizes. Beneath those piles of dirt, ants are building their underground homes.

That’s what I found out from my friend Rob Clark, an entomologist who studies bugs on plants. His job is to figure out if bugs make a plant sick or help the plant grow.

He told me ants are one of the most diverse insect families. Scientists know about nearly 13,000 species—and each ant species makes a different kind of nest.

Carpenter ants might make their nests in dead wood. Acorn ants make their nests in small twigs and acorns. Then there are ants that create massive underground mazes that are like cities just for ants.

Ants are pretty good at digging underground tunnels with their little jaw-like mouthparts, too.

“The workers use their mandible to carry the dirt and make space for the queen ant and the larvae,” said Clark. The larvae are their babies who will grow into workers.

Some ants, like harvester ants, will dig nests up to ten feet deep. While some ants make hills with the dirt they dig out, other ants make mounds they’ll actually live inside.

Thatch ants can make mounds that are up to four feet tall. The ants move around a lot of soil and bits of plants to shape their home. They like to build the mounds in a sunny spot, Clark said. Ants don’t like the cold. The babies need a warm environment and so do the workers.

Clark told me he actually saw one of these mounds while he was out in the field and thinking about your question. There were a lot of busy ants crawling around the outside and the inside of it.

It turns out, almost all ant nests start out with a young queen who has never had a colony before.

The queen excavates a small hole in the ground and picks up the soil with her mandibles. She will lay a few eggs and the ants that hatch will become workers.

“As she lays more eggs and more workers grow up, they have to expand the size of their house,” Clark said.

While ants can take care of the house, they can also help with jobs like farming aphids, another little insect.

Aphids have sugary poop, called honey dew, that comes from the sap they eat. Ants eat honey dew and protect the aphids from other predators, like a shepherd tending to a flock of sheep. It’s all part of something called mutualism, which means two living things helping out each other.

Now you know, ants on our planet make different kinds of nests, but they do it for similar reasons. They need to create a safe place for their colony to eat, work, and live. A single colony can contain thousands of ants and they all help each other survive.

Next time you see an ant hill, think about all the ants that made it and that there is a whole little world beneath it.

Sincerely,
Dr. Universe

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Dr. Universe: Do robots have their own language? And is there a translator? – Hank, 8, Virginia

Dear Hank,

Robots do have their own language—and yes, there’s a translator.

That’s what I found out from my friend Manoj Karkee, an engineer at Washington State University who is also really curious about robots.

Karkee and his team work on lots of robots that help farmers do important jobs. They can program robots to do different tasks such as pick apples or pull weeds.

Robots are machines that use computer languages to work. But this language is different than the one humans use.

The English language, for example, is made up of more than a hundred thousand words which are made up of just 26 building blocks called letters. Robot languages are built on just two basic building blocks.

“In a very basic form, computers, and for that matter robots, run with ones and zeroes,” Karkee said.

You might think of these ones and zeroes kind of like a light switch. The ones and zeroes help computers know how to send a current of electricity through robots or other electronics.

Zero stands for “off.” One stands for “on.” It’s all part of the binary system. In binary, for example, the number one is “0001” and the number two is “0010” and the number three is “0011.”

The combination of ones and zeroes can also represent letters to form words like “Hi.” The capital letter “H” for example is written as 01001000 in binary. The lowercase letter “I” is written as “01101001.” But there’s a bit of a catch.

“These days when we have to tell robots to do something, we don’t provide ones and zeroes,” Karkee said. “We provide a set of instructions in a language that is not like our human language, but that humans can understand.”

Lots of different computer scientists throughout human history have worked with those ones and zeroes to build more complex robot languages. These are called programming languages. Karkee and his team had to create a specific program, for example, to help the robots pick apples.

Karkee said that creating robot and computer programs requires a lot of math. So, if you want to program or build robots one day it is important to practice those math skills.

But the hard work pays off, especially when you get to build something new and amazing that can help people do important things.  Humans have programmed some robots to speak in human languages. Other people have programmed robots to translate human languages.

“Robots and other computer programs can act as a translator of human language. There are intelligent programs that can translate English into Spanish or Spanish to Nepali,” he said.

Of course, it took the work of programmers to tell the robots how to do that task in the first place.

Who knows, maybe one day you will help us create new languages for robots or come up with ideas to change our world. You might just become a translator yourself—connecting humans to the world of robotics.

Sincerely,
Dr. Universe

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Dr. Universe: How are coins made? -Dahlia, 10, Olympia, WA

Dear Dahlia,

In the United States, pennies, nickels, dimes, quarters, and other coins are made through the U.S. Mint. It turns out, they’ve been making a lot more coins than usual during the global pandemic. But more on that in a moment.

It takes both science and art to make coins. Coins are made from metals that have been mixed together. We call these kind of metals alloys. The very first coins in the world were made thousands of years ago in Turkey from electrum, an alloy of gold and silver. A penny is made from an alloy of copper and zinc.

According to the U.S. Mint, an artist will design the coin with all its details. Then sculptors create a model of the coin in clay or using a digital model and use it to make a plaster cast.

People scan the plaster cast using a computer and the computer’s software helps cut the coin design into the end of a metal cylinder. The metal cylinder is used to create more stamps, or dies, that will be used to press the coin design into metal.

Meanwhile, a machine cuts out flat circle shapes from sheets of metal. The circles are called blanks. The blanks heat up, get a bit soft, cool, go through water, and dry.

They go through a machine that raises the edges of the coin before going through another machine that presses the design into the coin.

Finally, the coins are bagged and shipped out to banks. We use them as we buy different things or do laundry at the laundromat.

Each month the U.S. Mint produces about 1 billion coins, which are made in Philadelphia, Pennsylvania and Denver, Colorado.

But because people are trying to prevent the spread of the novel coronavirus, they haven’t been exchanging many coins lately. There are fewer coins moving through the economy.

That’s what I found out from my friend Elizabeth Reilly Gurocak, an economist at Washington State University. She’d been noticing a lot of signs at restaurants and supermarkets informing customers that the country is having a coin shortage.

Your question even inspired her to start collecting coins from around the house and from family members. She takes the coins to counting kiosks at stores or to the bank to exchange for paper money.

“I’m going to start paying for things with coins just to put them back in the economy,” she said. “I’m going to be like the coin fairy!”

To help add more coins to the economy the U.S. Mint also plans to make about 1.65 billion coins each month for the rest of the year. You can help with the coin shortage, too.

“Empty those piggy banks,” Reilly Gurocak said. “Bring coins to the bank to exchange for paper money, buy things with coins, or take them to coin kiosks. We can solve this problem together.”

Sincerely,
Dr. Universe

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Dr. Universe: Can dogs tell time? -Sam, 8, Indiana

Dear Sam,

Dogs might not use clocks to tell time like humans do, but they are pretty good at following a schedule. They often know when it is time for a walk, dinner, or sleep.

A lot of animals rely on something called a circadian rhythm, a 24-hour cycle, to help them figure out when it is time to do different things. This system is sort of like an inner clock.

That’s what I found out from my friend Lynne Nelson, a veterinarian and researcher at Washington State University who takes care of lots of animals.

The circadian rhythm system is controlled by light. Humans’ ability to sense light is part of the reason why they are awake and alert during the day. And that’s why when it’s dark out, they go to sleep.

Different animals can have slightly different circadian rhythms. Cats, for example, are diurnal animals. They go out at night and sleep a lot during the day.

In a way, humans have helped dogs learn to tell time. When humans train dogs, dogs learn how to interact with both their humans and their environment.

“Dogs are training their brains based on different events, like owners coming home or when the food is going to come out,” Nelson said.

She also told me about something called entrainment, or the interaction between an animal’s circadian rhythm and the environment. You can think of it sort of like the way your stomach growls to signal that it is almost time for lunch.

“Dogs and cats know when they normally eat. So, they start to get hungry before then and start to bug their owners—even before they put the food out,” Nelson said.

All these things are entrained based on certain genes that control the development of different traits, as well as wiring in our brains, Nelson said.

“It all goes on in our brains and it happens without us even anticipating or knowing,” she adds.

There are some animals that not only have daily schedules, but seasonal schedules. We see this in animals that migrate or hibernate. They get cues from nature in the form of daylight and temperature. As winter approaches, bears know it is time to make their move because days get shorter and the air gets colder.

Nelson is really curious about bears. She said bears are really good at knowing schedules, including when it is the best time to get into people’s trash cans. They use clues from their environment, along with their circadian rhythms, to know when humans will put out the trash. Then they can look for a snack.

“Animals that are food-motivated like dogs and bears can become especially attuned to telling time because of special treats,” Nelson said.

When dogs aren’t eating or playing, they spend a lot of their time sleeping. Dogs sleep for around 14 hours or so a day. No matter the hour, it is almost always prime time for a nap.

Sincerely,
Dr. Universe

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Dr. Universe: Why do we need to eat and drink? -Victoria, 7, MN

Dear Victoria,

Just like a car needs gas to run, food is the body’s fuel. Food gives us energy, or the power to do work. It helps us run, jump, think, and do all kinds of things.

That’s what I found out from my friend Alice Ma, a dietician at Washington State University.

When you take a bite of food it goes down your throat, or esophagus, and down into your stomach. In the stomach and small intestine, things like bile, acid, and enzymes help digest, or break down your food so your body can absorb the parts it needs.

Food also contains carbohydrates, a substance rich in energy that is made up of carbon, hydrogen, and oxygen.

Carbohydrates can give us a lot of energy, especially when they come from foods like grains, pasta, rice, veggies, breads, legumes, and nuts.

Here’s how it works: the body breaks down carbohydrates into simple sugars, which get absorbed into your blood.

Sugar levels rise and your pancreas—an organ down on the right side of your belly—releases something called insulin, which helps move the sugar into your cells. Your cells can now use the sugar to produce energy, or store the sugar for later use.

There are all kinds of different foods to try in our world. One of Ma’s favorite ingredients is peanut butter. She likes to put it on top of her pancakes, cook it into curry, and dip spring rolls into a peanut butter sauce.

“I cook a lot of different things,” Ma said. “I’m always experimenting.”

She said one question she also gets is, “What would be the one good food to take with you if you were stranded on a deserted island?”

“There’s not one single food that everyone can eat to power everything,” she said. “You need a variety of foods.”

Food also contains lots of different parts such as vitamins and minerals that get absorbed as digestion happens. Protein from foods like meat and peanut butter get stored in muscle, skin, and other tissues and organs. Calcium from things like cheese or green leafy veggies can help the heart pump and keep bones strong.

As a dietician at WSU, Ma helps plan and create meals that fill the bellies and power the brains of thousands of university students. She also encourages people to drink plenty of water.

Water is important to our cells, along with our organs and tissues. In fact, water is what makes up most of our blood. Blood helps carry things like oxygen and nutrients through our body.

We lose a lot of water everyday through things like breathing, sweating, and going to the bathroom. That’s why it is so important to drink water every day.

While food and drinks are important to our health, they are also a big part of culture. Humans celebrate entire days about food and throw festivals to appreciate different cuisines. What kinds of foods do you celebrate in your family? Tell us about it sometime at Dr.Universe@wsu.edu.

Sincerely,
Dr. Universe

P.S. If you or someone you know needs access to food or wants to donate to a food bank, search the Food Finder for more information: https://foodfinder.us/

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Dear Dr. Universe: I am wondering if birds can smell because I have chickens and have seen their nostrils! –Lila, 9, Philadelphia, PA

Dear Lila,

Birds have nostrils, or nares, on their beaks that can help them smell all kinds of things.

That’s what I found out from my friend Dave Oleyar, a scientist with HawkWatch who recently taught a course on ornithology at Washington State University.

He said that when an animal breathes air, they can also breathe in different scents, or combinations of molecules.

The nose has receptors that pick up on scents and send information to the brain, including a part called an olfactory bulb. It’s all part of the olfactory system. You have an olfactory system, too. This system can help animals navigate the world through a sense of smell.

Maybe you’ve used your olfactory system to smell your breakfast, lunch, and dinner.

Birds can also use their olfactory systems to sniff out food. Oleyar told me about a few different birds and their amazing smell abilities.

The kiwi bird uses its long bill to dig into the dirt. Its nostrils are on the outside and very tip of its bill.

“It’s thought that they use that sense of smell to pick up chemicals emitted by their food. Grubs, worms, and other things that are in the ground,” Oleyar said.

Oleyar said one bird of prey that has a really great sense of smell are turkey vultures. He said vultures are scavengers, meaning they eat dead animals.

“They have an incredible sense of smell. They use their nose to pick up chemicals from things that are decaying,” he said.

Turkey vultures have one of the strongest senses of smells among birds. They have been known to smell food that was over a mile away.

But albatrosses, big sea birds that can have wingspans around ten feet, have been known to sniff out food from even greater distances—about 12 miles away.

These big seabirds can pick up chemicals from dead fish or groups of fish. They can even smell the scent that krill give off when they are eaten by fish. That helps them find the fish via the krill.

Birds don’t just have a sense of smell, but many emit different scents of their own. Some birds may use their noses to smell for other birds. This can help them find their family or even start a family of their own, kind of like a game of smell-and-go-seek.

The male crested auklets have little orange feathers on their heads that they use to attract females. But they also give off a citrus scent, along the lines of lemons and tangerines, that the females can use to find them.

While a sense of smell is helpful for birds, it isn’t the only useful or even sometimes the strongest sense—they also use their senses of hearing, sight, and taste. The next time you watch your chickens, or other birds in the neighborhood, maybe you can observe how they use all these senses.

Sincerely,
Dr. Universe

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Dr. Universe: What are bees’ wings made of? -Natalia, 13, Kennewick, WA

Dear Natalia,

Bee wings may be small, but they are really strong. I learned all about bee wings from my friend Melanie Kirby, a honey bee researcher at Washington State University.

Kirby said you can think about bee wings as if they were a kite. If you make a kite out of thin tissue, it might rip. But if you make it out of a strong plastic film it will be stronger.

Bee wings are made of a material called chitin (KITE-IN) and it’s a lot like keratin, the material that makes up your fingernails. Chitin is what makes up the wings on each side of the bee’s body.

There are the forewings, which are longer and the hindwings which are shorter. When a bee isn’t flying, the hindwings often get tucked in behind the forewings.

Kirby told me that chitin covers the bee’s entire body and is what makes up the exoskeleton. While you have a skeleton under your skin, bees wear their skeletons on the outside of their bodies.

Bee wings are very thin and transparent, which means you can see through them, a bit like clear glass. But the strength of the material can help a bee carry a lot of nectar. In fact, a bee can carry a load of nectar that is almost equal to its body weight.

I found out chitin isn’t the only thing that makes up bees’ wings. There are also veins filled with hemolymph, or insect blood. And there are air tubes and nerves, too. These parts add strength and stability to the wings, Kirby said.

The veins are kind of like the cross sections of the sticks in a kite. Different types of bees have different vein patterns on their wings.

“Scientists can identify bees by looking at the wings close up under a microscope. And like a kite it has a cross section of sticks, or the veins, which reinforce the wing,” Kirby said.

The wings are connected to muscles in the middle section of the bee, or its thorax. Small barbs called hamuli can connect the forewing and hindwing together. When the hamuli are connected, the wings come together to act like one big kite. This helps the bees glide as they fly.

When the hamuli are separated, the wings are like little rotary motors moving around in a circle like a propeller. This helps the bees get lift and steer themselves in different directions as they fly.

Bees’ wings are the last thing to form before they emerge as adults (bees also develop through metamorphosis similar to butterflies). Their wings will carry the bees through their whole lifetime. Researchers estimate that bees get about 500 miles on their wings before they start to tear and wear out.

During their lifetime, bees will fly from flower to flower. They move tiny grains of pollen around to help plants grow things like nuts, fruits, and vegetables. It’s called pollination. The next time you hear the buzz of a bee’s beating wings remember how important they are to our world and how they help us have food to eat.

Sincerely,
Dr. Universe

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Dr. Universe: Why do some birds cheep loudly while other birds cheep quietly? -Traver, 4, Indiana

Dear Traver,

That’s a great observation. Birds make all kinds of sounds and for lots of different reasons.

When I got your question, I called up my friend Jessica Tir, a graduate student at Washington State University who studies songbirds.

She said one of the main reasons a bird will make a loud sound is to attract a mate. When the birds find each other, they can make a nest for their eggs and wait for babies to hatch.

Songbirds, such as swallows and starlings, learn their songs when they are babies. Usually, they learn the song from their dad.

“That’s the song they are going to sing for the rest of their life,” Tir said.

One of Tir’s favorite bird sounds is the varied thrush, an orange and black songbird that lives in the Pacific Northwest. They are known for their calls that sound a bit like a UFO. She also told me not all birds have songs. Some birds like hawks and seagulls make noises such as caws, clucks, or screeches.

Birds may also get loud because they want to let other birds know they’ve found some food. It’s almost like an invitation to dinner. Baby birds may also chirp quietly or loudly when they are hungry.

In the lab at WSU, Tir records songbirds’ songs on microphones to learn more about how they communicate with each other, especially when they are hungry. The research will help us learn more about communication and how much food there is some birds’ habitat.

Birds may also get loud when they sense danger in their environment. When birds hear a fellow bird send out a warning, everyone might get really quiet. You might not hear a peep. This can help the birds stay safe from predators.

If birds are being a bit quieter, it might just mean they are sort of chatting throughout the day. Different situations may call for different volumes. This is true among humans, too. Maybe a friend yells across the playground to get your attention or maybe you have to be really quiet and put on your listening ears during story time.

While humans can make sounds with help from their vocal cords, birds use a part called the syrinx (SEE-RINKS). Ostriches have a much bigger syrinx than, say, a tiny swallow, but they work in similar ways.

As air moves through the syrinx, it helps produce the different sounds. It sort of reminds me of how air moves through a musical instrument.

And those bird sounds can make my ears perk right up. Maybe they’ve caught your attention too and inspired you to look for the source of the sound.

The next time you go outside, keep your ears out. How many different kinds of birds can you hear? Can you find the bird making the sound?

Sincerely,
Dr. Universe

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