Dear Dr. Universe: How does digestion work? –Abi, 12, U.S.; Megha R., 11, Dubai

Dear Abi and Megha,

All around the world, animals are eating all kinds of different foods. Our foods might be different, but one thing is true for all of us: We have to digest.

I decided to visit my friend Bob Ritter to find out how this works. He’s a researcher here at Washington State University who is really curious about the connections between our brain and stomach.

“What we eat at lunch is almost completely digested by the time we are ready to eat dinner,” he said. “It is digested, absorbed, and the food has totally changed.”

The molecules that make up a piece of meat or a vegetable on your plate are too big for your body to use, at least at first. The body breaks down the food using a nearly 30-foot-long digestive tract that runs from your head to your rear end.

And while we may all digest, different animals have different kinds of tracts. Ritter explained that a python could go for about six months without food. When it comes time to eat a meal, usually in a single gulp, the python’s digestive system will suddenly grow bigger.

Unlike pythons, humans need to eat much more often. The human digestive system can help you digest a meal in just a few hours or less.

Muscles in your stomach squeeze and occasionally grumble to tell your brain that you’re hungry. When you smell or even see food, your mouth starts to water. Even the sound of food going into my bowl makes my mouth water. This saliva helps us soften and break down food so we can swallow it.

The muscles in the esophagus, a long tube in your throat, help push food down into your stomach. There, your stomach acids and enzymes help you break down the food. Most of the food is now about the size of a grain of salt.

These little pieces move onto the small intestine, which is pretty big, despite it’s name. It’s here where the big chemicals in food are broken down to small ones that the body can absorb into your blood, like sugars, amino acids, and fatty acids.

There is a lot of surface area that makes it possible for your body to absorb these helpful nutrients, too. If you unfolded your small intestine on a flat surface, it would likely cover a tennis court, Ritter said.

Once the nutrients are absorbed, the large intestine absorbs water from the digested mix and helps give it back to your body. Some harder parts are left behind and get ready to leave the body. Pretty soon, nature calls.

Whether you are a cat, a python, or a human, the digestive system not only fuels your body, but also protects it. Humans even have a special lining in their stomach that gets replaced every few days to protect them from invaders like toxins or bacteria. It’s something to chew on the next time you sit down for dinner.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your own question to Dr. Universe at AskDrUniverse.wsu.edu.

Hi Dr. Universe! I’m Bree and I just wanted to ask, how do cats land on their feet?  -Bree, 10, Williamsburg, VA 

Dear Bree,

Curiosity can lead us cats to some pretty great heights. We like to climb trees and sneak along tall bookshelves. Sometimes we might have a bumpy landing, but more often our amazing cat reflexes help us land on our feet.

Like my fellow felines, I’ve been using my reflexes to fall on my feet ever since I was about three weeks old. But even I wasn’t sure exactly how this worked or why it doesn’t work all the time. I decided to visit my friend Matt McCluskey, a physicist at Washington State University, to find out more about it.

At first I thought the answer to your question might have to do with our tail. I suspected that as cats fall through the air, the tail helps us find balance. But it turns out cats without tails can land on their feet, too. There’s a little more to it.

McCluskey and I came across this fact in a study from a scientist in London who investigated your very question more than half a century ago. The scientist slowed down pictures of falling cats and observed their movements. He found that the cats landed in a very particular way. He published an article about it in New Scientist called, “How does a cat fall on its feet?”

Looking at the pictures of falling cats, he found that we first use our sharp ears and eyes to help us figure out which way is up. Our head, the lighter end of our body, twists one way. Then the heavier end of our body, the rear, follows. We use this movement to try to maneuver our bodies back to normal and brace for landing. Scientists call it the air-righting reflex. It’s what helps us go from free falling to feet on the floor, often in less than a second.

Our flexible spine and lack of a collarbone also make it possible for us to arch our backs in mid-air. We can arch our backs when we feel threatened, when we stretch, or to help us land after our body twists. Our arched backs help stabilize our bodies, preventing them from rotating, just before landing. McCluskey explained that even though our tails aren’t fully responsible for helping us land on our feet, they do help us be more stable upon landing.

There are actually so many cases of cats falling out of windows that veterinarians have a name for it: high-rise syndrome. Some researchers have found that cats who fall from greater heights have a better chance of landing on their feet than cats who fall shorter distances. It might be because they don’t have enough time to go through all the different movements that help them stick the landing. Sometimes we stumble. Sometimes we land in style. It’s all feline physics.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science education project from Washington State University. Send your own question in at askDrUniverse.wsu.edu. 

Why does the Earth spin?
–Morven, 8, Dundee, Scotland; Judith, 9, Sabah, Malaysia; Mara, 11, USA

Dear Morven, Judith, and Mara:

No matter how still we stand, or if we’re in Scotland, Malaysia, or the United States, we are always spinning. Our Earth spins at a constant, very fast speed as we make a trip around the sun.

But it’s not just the Earth that spins, said my friend Guy Worthey, an astronomy professor at Washington State University. The moon, the sun, and almost all the other planets spin, too.

Your question actually has a lot to do with our early solar system. Scientists think the solar system started out as a kind of giant pancake, Worthey said.

Not like a pancake you’d eat for breakfast, of course. It was more like a giant pancake-shaped cloud of gas and dust. The pancake was a unit, with all parts of it spinning in the same direction, Worthey explained.

“When the planets started to form out of this big mass of gas, they shared not only the same mix of material, but also a sense of spin,” he said. “Like little whirlpools in a bigger whirlpool.”

The Earth has been spinning for billions of years, but it’s also been slowing down ever so slightly. Some scientists are interested in tracking this, too. They’ve found that the spin slows just a fraction of a second each year. If the Earth keeps this up, it would take trillions of years before it ever stopped spinning,

The length of a year, 365.24219 days, which is how long it takes the earth to travel in a huge circle around the sun, is not changing very much. The length of a year is different depending on how a planet orbits in a huge circle around the sun.

Our Earth spins around on its axis, a kind of imaginary pole that runs through the planet from north to south. The Earth spins all the way around its pole to make one complete turn each day, or 24 hours.

But if you were to visit Venus, one day would last as long as 243 Earth days. Venus spins much slower than Earth. Scientists think that an object might have hit Venus and knocked it around a bit after the solar system formed, slowing its rotation. Uranus is another planet that spins in its own unique way. It’s got an unusual tilt that makes it spin on its side.

Our Earth also has a tilt. As it spins, it doesn’t sit upright on its axis. The imaginary pole that runs through the middle sits at an angle of 23.5 degrees compared to solar system north. This tilt makes it so that some parts of the planet get different seasons.

It’s exciting to know curious cats from all around our world are stopping to wonder about our Earth’s spin. Now, let me spin a question back to you. No matter how still we stand, we are spinning. But perhaps you’ve noticed you aren’t getting dizzy or flying off the planet. Why might that be? Send me your thoughts at Dr.Universe@wsu.edu.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Submit your own question at http://askDrUniverse.wsu.edu.

How do we remember stuff?
– Aidan, 11, Franklin, Indiana

Dear Aidan,

Our brains have an incredible ability to help us remember all kinds of stuff. Of course, memory isn’t perfect. Sometimes we forget our homework or where we left our favorite cat toy.

My friend Maureen Schmitter-Edgecombe, a scientist at Washington State University, is also very curious about memory. Her research focuses on using creative technology to help people who have serious memory loss.

She explained that an important part of how we remember has to do with our hippocampus. It’s a seahorse-shaped part near the middle of our brain that plays a role in forming new memories.

Humans who have a missing or damaged hippocampus, like those in the late stages of Alzheimer’s disease, can’t form new memories, but they can still retrieve some of their old memories.

If you are anything like me, you know that a single smell, song, or picture can take you on a trip down memory lane.

In fact, your question reminded me of when I was first learning about our solar system.

I was having a tricky time remembering the order of the planets. Until I found out about this: “My Very Educated Mother Just Served Us Nachos.”

The first letter in each word helps you remember the names and order of the planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. I repeated this phrase over and over again to help the new information stick.

Strategies like this can help us remember big chunks of information and lay them down as new memories.

Another important part of remembering is being really attentive to information as we learn it, Schmitter-Edgecombe said. A good night’s rest can help us stay alert during the day. Some scientists are even investigating questions about how sleep triggers changes in your brain that help memories solidify.

Schmitter-Edgecombe explained that once we attend to the information, we have to help get it into long-term memory.

One way to do this is to connect new information with something you already know. As you read, your brain may be making connections with other things that you’ve learned before. The connections between your brain cells strengthen and may make it easier to remember what you have read.

And we have quite a bit of space for our memories, too. According to the magazine Scientific American, if your brain worked like a TV’s digital video recorder, it would likely hold three million hours of TV shows. And it would need to be running for nearly 300 years to fill up all the storage space.

That makes strategies for remembering the important things even more useful. Creating songs, poems, or drawings can also help our brains create stronger connections to the new information. You could even try out a few of these memory devices and see what works best for you or your friends. Let me know what you discover at Dr.Universe@wsu.edu.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University.

Dear Dr. Universe: Why do we find some things scary? -Jack H., 8, UK 

Dear Jack,

While our fears might be different, we all get scared sometimes. Vacuums, dogs, and even cucumbers make my hair stand on end. Perhaps for you it’s spiders, the dark, or the thought of monsters under your bed.

My friend Michael Delahoyde is really curious about what freaks us out. As an English professor at Washington State University, he’s even taught a course about monsters.

Delahoyde explained that our brains like to categorize information to help us make sense of our world. But monsters sort of live between different categories.

“We are comfortable with animals. We are comfortable with humans. We’ve got the distinctions down,” Delahoyde said. “But when you have a monster, like a werewolf who is somewhere in the middle, then it freaks us out.”

We can’t quite put our finger on what is happening, so we feel a sense of uncertainty. Zombies also break categories and laws of nature, as they are both living and dead.

Every culture has its own monsters, too. One in Japan is the bakeneko, a supernatural, shape-shifting cat creature whose presence in stories is often seen as a sign that a strange event is about to occur.

Our hearts start pumping. Our pupils get bigger. Our hands get sweaty. We might even get goose bumps or chills. The fear center of our brain, a little almond-shaped part called the amygdala, gets to work.

Our brain and body are getting ready to make a decision about what to do in the scary situation. We have to decide whether to face it or run away.

In some situations, our response to this fight-or-flight situation can be thrilling. That’s why some people actually enjoy watching scary movies. They know they are safe, even if they occasionally have to cover their eyes with their paws.

My friend Jaak Panksepp, a researcher in the WSU College of Veterinary Medicine, is also curious about emotions, like fear, in animals.

All of our brains contain a fear system, he explained, which is designed to protect us from harm. When this system is at work, we have a feeling that can be described as scary.

While our ancestors may not have come face-to-face with werewolves, they may have encountered a saber-toothed cat. They would have to make a decision to fight it or run. The fear system automatically tells us to avoid such situations. It also helps us figure out, often in an instant, how to deal with similar frightening events in the future. Fear helps us survive.

Our personal fears can actually change, as we grow older, too. We might become fearful of new things or learn to become less afraid of the things we once feared, like dogs or monsters under the bed.

Do you have an idea for a monster of your own or a scary story to share? Send in your drawings or stories to Dr.Universe@wsu.edu.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send in a question of your own at askDrUniverse.wsu.edu.

Dear Dr. Universe: How do spiders make silk? Also, sometimes spiders hang down from the ceiling, when they climb back up, where does the silk go? –Johnny, 8, Pullman, WA

Dear Johnny,

Spiders can do some amazing things with their sticky, stretchy, and super-strong silk. Us cats are pretty curious about these little silk-spinning machines, too.

Besides chasing spiders around, I’ve watched them use silk to build webs, catch bugs, and protect their young spiderlings.

Some spiders will even eat their own web. Imagine if you could build your own house and eat it, too.

Spiders have lots of jobs to do and eating their web is one way they can get a bit of energy. It’s also a good back-up meal in case they don’t catch any bugs. After all, their silk is made up of protein.

Inside their rear-ends, or abdomens, spiders have a liquid made of watery proteins. They also have special, nozzle-like organs called spinnerets. Along with some chemical reactions in the abdomen, spinnerets help spiders transform those watery proteins into silky strands.

That’s what I found out from my friend Beverly Gerdeman, an entomologist at Washington State University. Like you, she’s also very curious about bugs and spiders.

Gerdeman explained that spiders have two or more spinnerets. The exact number depends on the kind of spider you are.

While it might look like spiders make just one strand of silk, they actually make a whole bunch of strands spun together like a rope.

The silk is extremely flexible and can stretch up to four times its original length. And even though it’s lightweight, it’s really strong. In fact, spider silk is stronger than a piece of steel the same size. It’s a great material for building things.

Not all spiders build webs, but a lot of them do. Different spiders can also spin out silk in different thicknesses for different jobs.

Some spiders will use the silk to go “fishing” for bugs, wrap cocoons around their young, and even travel long distances.

A lot of young spiders, for example, can throw up a line of silk and wait for a draft of air to carry it away. Then they can control their movement using their legs and silk—much like your friendly neighborhood Spiderman.

It helps them move their population around. Some pilots have reported seeing spiders drifting along more than 10,000 feet up in the air.

Spiders may throw up a line of silk to help them travel, but as you observed, they also drop their lines down.

I’m not a scaredy cat, but I admit I get a little surprised to see a spider in front of my nose.

Sometimes, the spiders will climb back up their line really fast. The silk doesn’t go back into the spinneret, though. It likely just gets knocked away in the breeze or the spider pulls it back up for a snack. Mm, protein.

Once they eat their web, some spiders will recycle it back into their abdomen, so they can keep on spinning.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your science question to Dr. Universe at askDrUniverse.wsu.edu.

What is Dr. Universe’s favorite experiment? -Garrett, 8th grade, Eastern Washington

Dear Garrett,
 
You know, your question reminds me of a couple other science questions from curious readers. Evangeline, age 7, wants to know why her hair is black. Sureya, age 8, wants to know why some people have curly hair.
 
It just so happens that one of my favorite science projects explores our questions about what makes us unique. It has to do with our DNA, or the blueprint for life.
 
Not too long ago, some of my friends at Washington State University showed me how to extract DNA—from a strawberry.
 
You can try it at home, too. You’ll need simple ingredients, including dish soap, meat tenderizer, rubbing alcohol, and strawberries. Find all the details at AskDrUniverse.wsu.edu/strawberry_dna.
 
Just like humans, strawberries and other plant life are made up of cells. Inside cells, you’ll find their DNA.
 
Your DNA contains the instructions for your eye color, hair color, and if that hair is straight or curly. These traits can be passed down through generations.
 
A strawberry’s DNA also holds information about the fruit’s color, size, and shape, and that it has seeds growing on the outside.
 
When we extract DNA from a strawberry, we have to bust through a few parts of the cell to get to the DNA. We start out mashing up the strawberries with a little water and pouring the smoothie-like liquid into a test tube.
 
Then we add a little dish soap to help dissolve a layer around the DNA called a membrane. Next, we add a bit of meat tenderizer to break up proteins that help hold different parts of the DNA together. But the DNA can’t separate from the rest of the ingredients without one final step.  
 
Add some cold rubbing alcohol to the mix and it will pull DNA up to the top of your test tube. When you try this out, ask yourself—does it look a bit like a booger floating in your tube? If so, you’ll know you’ve got the strands of DNA.
 
While living things carry around DNA in their cells all the time, it’s not every day people actually get to see it up close. That’s what my friends and I like most about showing people how to extract it.
 
If you want to turn this project into an actual experiment, you’ll need to test an idea or question about the extraction, too. What happens when you add more or less of an ingredient? Can you extract DNA from all vegetables and fruits? I’m sure you can think up even more questions to test out.
 
Give it a try one day and let me know how it goes. In the meantime, tell me about the latest science project you tried at home or school. Email Dr.Universe@wsu.edu or write to Dr. Universe, PO Box 641227, Pullman, Washington, 99164-1227.  
 
Sincerely,
Dr. Universe
 
Got a science question? Email Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

Why do volcanoes “die”? – Loretta, 11, Mexico

Dear Loretta,

Each volcano’s life is a little different. Many of them are born when big chunks of the Earth’s crust, or tectonic plates, collide or move away from eachother. The moving plates force hot, liquid rock, or magma, to rise up from deep within the Earth.

When things get super hot and lot of pressure builds up in the magma chambers, volcanoes can erupt. Some volcanoes can spew ash and lava several miles into the sky. Others will slowly ooze out lava.

Just as each volcano is unique, so are the reasons they go extinct. Generally, though, if a volcano doesn’t have a source of magma, it won’t erupt.

That’s what I found out from my friend John Wolff, a geologist at Washington State University. To explore more about how volcanoes lose their magma, Wolff and I headed to the plains of southeast Idaho. There, the remains of really old volcanoes are buried underground.

Millions of years ago, we would have been able to see these volcanoes at the surface. They might have been spewing out lava and ash. But now, they no longer have their source of life.

If you are anything like me, you might be wondering what on Earth happens to the magma. Wolff is really curious about this, too.

He explained that volcanoes, and all of us, are riding on pieces of the Earth’s crust.

These pieces of crust move very slowly—just about as fast as our fingernails grow. They move over heat sources, zones of hot, upwelling rock from deep in the Earth’s interior. It melts the crust when it gets near the surface to fuel the volcano.

“It’s burning a hole in the plate,” he said. “Just like if you passed a plastic sheet over a candle flame.”

Eventually, when volcanoes have rafted away from the heat source, they falter and die.

As the Earth’s crust moved, slowly but surely, over millions of years, the magma that was under old volcanoes in southeast Idaho ended up in Wyoming—under a big super volcano.

Never having seen a super volcano before, I imagined a huge mountain erupting tons of lava. You can imagine my surprise when Wolff explained that this super volcano was actually Yellowstone National Park.

Millions of years ago, the Yellowstone super volcano erupted and collapsed. There is still magma under Yellowstone, but we don’t expect it to erupt anytime soon.

While a volcano may need to have magma to stay alive, there are still volcanoes that have a magma supply and can sleep for millions of years—and you thought us cats slept a lot.

Some scientists are really curious about how the landscape changes, both above the ground and below it. In fact, they ask questions that are a lot like yours, Loretta. Who knows, maybe one day you could help us investigate the lives of volcanoes.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your question in at AskDrUniverse.wsu.edu.

Why do cheetahs run fast? –Shanyu, 9, London, UK

Dear Shanyu,

Cheetahs are in really good shape. Not only are they good runners, but the actual shape of their body helps them move at incredible speeds.

As the fastest cats on the planet, they can reach 75 mph. Whenever I lace up my shoes and run, I can only reach about 30 mph. Us tabby cats are pretty quick, but not quick enough to outrun a cheetah.

The difference has to do with a cheetah’s amazing anatomy—everything from its head and skeleton to its muscles and feet.

That’s what I found out from my friend Bethany Richards. She studies veterinary medicine here at Washington State University and is president of the Zoo, Exotics and Wildlife Club.

“Cheetahs are so lean and just cool,” she said, recalling a recent safari in Africa, where she saw them running around.

She explained that a cheetah’s spine is very flexible. It’s more flexible than other cat spines. The spine is so flexible that it allows the cheetah to quickly move its two back feet ahead of its two front feet. Along with some unique hips, this movement helps the cheetah get more distance per stride.

This allows the cheetah to take four long strides each second. In fact, if you slow down video of a sprinting cheetah you see it spends more time in the air than on the ground.

A cheetah also has strong muscles to help the spine move. They are made of special fibers that are ideal for sprinting short distances. Their small skulls and narrow bodies keep the big cats aerodynamic as they zip through the air. They also use their big nostrils and big lungs to breathe as they run.

Richards explained that another important tool that cheetahs use for speed is their claws. Unlike the rest of us cats, cheetahs can’t retract their claws into their paws. This lets their paws work more like cleats. They can dig into the ground and not have to worry about swerving out of control at high speeds.

Cheetah populations are actually pretty small. They are an endangered species—they are at risk of extinction—and the mothers don’t have too many cubs. They need their speed to survive, Richards explained.

“It made sense that the fastest cats would be able to get to the best food to provide for their limited number of young,” she adds.

Of course, speed can be very useful when looking for dinner. But once the cheetahs catch their prey, they have to rest before eating. Scientists have also found that a cheetah’s agility—its ability to turn quickly and sharply while running—may be just as important to the hunt as speed. Put the two remarkable abilities together and you’ve got one cool cat.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your science question to Dr. Universe at AskDrUniverse.wsu.edu.

What is cheese exactly? –Mark, 11

Dear friends,

Cheese is delicious. At least, that’s this cat’s professional opinion. For the more scientific answer, I visited the cheese makers here at Washington State University.

Cheese is the fat and protein from milk, said my friend John Haugen who runs the WSU Creamery where they make Cougar Gold Cheese.

At the creamery, students test milk from the dairy to make sure its fat and protein ratio is just right for cheese. They also heat up the milk to get rid of any bad bacteria—it’s a process called pasteurization. Not all bacteria are bad, though. In fact, some bacteria are really helpful for making foods, including yogurt, pickles, and cheese.

All cheese is made with a kind of lactic acid bacteria. These tiny little organisms are so small you would need to use a microscope to see them. They eat the sugar in the milk and make acid. The acid gives the cheese its tangy flavor.

There are even certain kinds of bacteria that are in charge of making the holes in Swiss cheese.

As Haugen explained how they add bacteria into the milk, I wondered how the liquid mix becomes a solid.

Haugen said that we need an enzyme, a protein that has a very special job to do. In cheese, enzymes work on protein in milk to break the bonds that keep it together. The protein opens up and sticks to other proteins around it to create a solid. If the enzyme does its job, the liquid will thicken, or coagulate.

“It’s almost looks like thick yogurt,” he said.

After that, the cheese makers will cut up the coagulated milk. When it starts looking a bit like cottage cheese, a machine pumps the mix onto a metal table.

This mix is partly made up of whey, which is mostly water. The other part of the mix is the soft, fresh curds. You can eat the cheese curds. They are tasty. Trust me. But they aren’t quite officially cheese yet.

First, the student cheese makers will pack the curds together into big loaves. They will flip the loaves over several times in a process called “cheddaring.”

If you wanted your cheese to be stringier, softer, crumblier, or harder, you might treat it a little differently. But at the creamery, Cougar Gold gets cheddared, chopped up, and salted to kill off some of the remaining bacteria and to keep it from liquefying.

The cheddaring process is actually named after the place where cheddar was first invented—Cheddar Gorge in England.

During the 12th century, people kept their cheese in caves. The temperature and humidity was just right for storing cheese.

At the WSU Creamery, cheese is also stored at just the right temperature, but inside tin cans.

“It’s almost like its own little cheese cave,” said Haugen. The cheese will stay in the can one full year before we eat it. Aging the cheese helps bring out the flavors.

After my visit to the creamery, I learned cheese is not just delicious. It’s milk, bacteria, enzymes, and salt. It’s science.

Sincerely,
Dr. Universe

Why do leaves change color? –Lucy, 5, Seattle, WA
 
Dear Lucy,
 
Ever since I was a kitten, I’ve loved picking up big maple leaves in the fall. I’d take them home, put them under a piece of paper, and rub the side of a crayon over the top. It makes a great print of the leaf.
 
Leaves actually get their color from things called pigments. While scientists can use chemicals to make different crayon colors, nature can use pigments to create its own colors.
 
When leaves are green, they have a pigment called chlorophyll. Chlorophyll is not just important for color, though. Plants also need chlorophyll to collect energy from the sun to make their own food. Imagine if you could soak up sunshine, water, and stuff from the air to make your own food. That’s what plants do. They make their own food in a process we call photosynthesis.
 
My friend Asaph Cousins is a scientist at Washington State University who knows a lot about how plants function. He’s really curious about photosynthesis, too.
 
“It’s a remarkable process that helps convert energy from the sun into food for plants,” he said. “It’s a key part of life on our planet.”
 
Cousins explained that chlorophyll has the job of soaking in the sunlight and using energy to convert some gas from the air into sugars. In the spring and summer, when the sun is out, a plant needs to make a lot of chlorophyll to help create food. But in some places of the world, like here in the Pacific Northwest, the sun starts to set earlier and it gets colder in fall.   
 
As we pull out our scarves and mittens, trees get ready for the changing season in their own way. Their growth decreases and they start to store up some of that energy they made earlier in the year. This means photosynthesis slows down and they don’t need as much chlorophyll to make food. Photosynthesis slows and the chlorophyll inside the leaves breaks down—so we see less green before the leaves fall off.
 
Chlorophyll isn’t the only pigment in a leaf. There are also carotenoids, which are pigments that give fall leaves the yellow and orange colors we see. It’s the same pigment we find in sunflowers and carrots, too. You may remember from our question about apples, that the pigment called anthocyanin is responsible for the red color in the fruit. The same is true with red leaves.
 
Because there is so much chlorophyll in the leaf, it isn’t until the chlorophyll breaks down that the fall colors really start to pop out. Of course, not all trees lose their leaves in fall and grow new ones back in the spring. But the ones that do lose their leaves—the ones we call deciduous trees—can transform their colors in just a matter of weeks.
 
Once the leaves finally fall to the ground they make for some great piles to jump in, inspiration for art projects, and beautiful autumn scenes.
 
Sincerely,
Dr. Universe 
 

Try it out! What can you create with leaves? Send a pic of your own fall leaf project to Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

How do lunar rovers work? -Pedro, 10

Dear Pedro,

When I got your question, I started to imagine what it would be like to drive a rover on the moon. As we bounced along craters, we could kick up moon dust and stop to gather samples of moon rock.

Rovers on the moon, and other kinds of exploration vehicles, have helped us learn about places that are hard for humans to reach on their own. Each rover has a mission and they need a few key things to work.

First, a rover vehicle needs a power source. Some rovers are battery-powered, like the lunar roving vehicle. Other rovers use solar panels to harness energy from the Sun. These solar panels are usually on top of the rover. The electricity they produce powers the wheels and the sensors the rover uses to conduct science experiments.

Scientists and engineers ask questions about what job they want a rover to do, and the environment where the rover will be working. The moon, for example, has no air. The tires we Earthlings have on our bikes and cars wouldn’t work on the moon. In fact, these kinds of tires would explode there. On lunar roving vehicles, tires are made up of a steel wire mesh. They support the rover’s weight, and astronauts don’t have to worry about getting a flat tire.

While lunar roving vehicles required astronauts to drive them, some rovers go on solo missions. Well, they aren’t totally alone. As they dig in the extraterrestrial soil and take pictures of these distant places, they communicate what they learn back to Earth.

Scientists send out computer commands that tell the rover what to do using super-powerful radio transmitters. The rover’s antenna helps send and receive the messages. It takes about a one second delay to command a rover on the moon and up to 22.5 minutes to communicate with one on Mars.

I decided to meet up with my friend Phil Engel to learn more about Mars rovers. He and a team of fellow student engineers from Washington State University recently brought back their award-winning rover from a global competition at the Mars Desert Research Station in Utah.

Their rover has an arm, or excavator, to dig for samples of dirt. The rover also uses sensors—like those you can buy to test your garden’s soil—to get the scoop on what’s in the dirt, including its temperature, humidity, and saltiness.

“What a rover vehicle does on Mars is pretty simple,” Engel said. “But what we are doing here on Earth with that rover is pretty extraordinary.”

While it might not sound exciting to look for dirt, these samples can tell us a lot about the planet or moon. The elements in these samples can help us find answers to some of our big questions about life on Mars—if there used to be life there, if there’s life now, or if life could be there in the future.

Whether on Mars, the moon, or even remote places on our own planet, rovers roam around to help us explore and discover. Who knows—maybe one day you’ll help find new ways to make them work and build rovers that are out of this world.

Sincerely,
Dr. Universe
Ask Dr. Universe is a science-education project from Washington State University. Send your question to Dr.Universe@wsu.edu

Watch the WSU team’s rover here: https://askdruniverse.wsu.edu/2016/06/23/lunar-rovers-work/ 

Why are apples red? -Emily, 5, Seattle, WA

Dear Emily,

Just the other day I was biting into a crunchy, delicious red apple when I was reminded of your question. I started wondering why apples are red, too.

I called up my friend and apple expert Kate Evans, a scientist here at Washington State University. Her research helps us develop new kinds of apples.

Before she answered your question, she had a question for us to wonder about, too.

“What might the benefit be for a tree to have red fruit?” she asked. I thought about it for a moment. Then I remembered that in nature, colors could sometimes help send a message to plants and animals.

The message might be “Don’t eat me,” as is the case of some brightly colored poisonous frogs. Other times it might be a chameleon using its colors to attract a mate, like saying “Look over here!”

Evans explained that the apple’s red color might just be a way of telling hungry animals, “We are delicious.”

Long before humans were shopping for apples at the supermarket, bears were scavenging for the fruit in forests. Bears have a good sense of smell and pretty good vision that helps them look for food. One idea is that bears are particularly attracted to red, a color that really pops.

“A red apple is kind of a pretty, attractive, easy-to-see piece of fruit, especially against the green leaves,” Evans said.

When bears see the red fruit, they eat it, digest it, and poop out the seeds. In fact, Evans said, the point of the tree having fruit at all is to help the tree spread its seeds. That way new generations of trees can grow.

Of course, you may have noticed that not all apples are red. Some are yellow, pink, or green. Red apples get their color from anthocyanins. These are pigments, or natural colorings, that develop as the apple grows. We also find these pigments in cranberries, raspberries, cherries, cabbage, and other red or purple foods.

Whether you are on four legs or two, the red color can be really appealing, Evans said. A lot of humans like to eat red apples, too. Here in Washington State, we produce more than 2 million tons of apples each year, far more than any other state.

Another way to think about the answer to your question may be to look at how we see different colors. When we look at a red apple, it’s absorbing colors from the sunlight. It absorbs all the colors of the rainbow—except for red. The red light reflects off the apple and our brain and eyes work together to let us know what color we are seeing.

Red is a color that can be appealing to both humans and other animals. It’s also one of my favorite fall colors. To celebrate the season, I’m off to pick some red apples and press them into delicious cider.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your question to Dr. Universe at AskDrUniverse.wsu.edu.

How many suns are in the universe? -Kristen, 8, Pullman, WA

Dear Kristen,

Our sun is really one big star. And there are billions and billions of stars in our universe.

“More than we can even count,” added my friend Phil Lou. He’s an expert on solar energy here at Washington State University. He’s really curious about finding ways to power homes and schools using energy from the sun.

“Most of the energy and life around us that we know is linked to the sun,” he explained. Then we put on our sunglasses, slathered on some sunscreen, and headed out to explore.

As we walked along, we spotted some grass and plants. Lou pointed out that plants use energy from the sun to help make their own food. A leftover from this process is the oxygen that we breathe.

Humans can also get energy when they eat plants—or eat the animals that once ate the plants. The sun also puts energy into the oceans and evaporates water, which helps keep water moving through the planet. The sun heats land and air which causes wind and weather. All this energy from the sun is really important to support life on Earth, Lou explained.

“It also makes Hawaii and Fiji great places to go,” he added. It sometimes makes for nice sunny catnaps here where I live in Washington state, too.

Even the oil, coal, and gas we get from the ground and use to power cars and make electricity started with energy from the sun. These kinds of fuels came from old decomposing animals and plants—animals and plants that got their energy from the sun’s rays.

Stars, like the sun, can come in all kinds of colors, shapes, and sizes, too. Scientists put them in different categories depending on their size, brightness, and other characteristics. According to these rules, the sun falls into the category of a yellow star.

Scientists have also calculated that it’s about 27 million degrees Fahrenheit inside the sun’s core and more than 9,000 degrees Fahrenheit on its surface. Thankfully, we are 93 million miles away, so we get just the right amount of warmth and energy from it.

Although our sun might be the closest star to us on Earth, it certainly is not the biggest or brightest star in the universe.

“Our sun is fairly puny compared to some other stars,” Lou said.

In fact, if you put our sun next to the giant star VY Canis Majoris, you could barely see it. It’s a speck, like a grain of sand next to a basketball. Consider the fact that you could fit a million Earths in our sun and you can start to realize just how big some stars can get. We are still learning about different stars and if there might be more sun-like stars out in our universe.

“It gives us something to really ponder,” Lou said. “Isn’t that great?”

We would love to hear more questions from you about solar energy and how it works, too. Or send us your own ideas about how to use energy from the sun to power our world. Write to Dr. Universe at Dr.Universe@wsu.edu.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your question to Dr.Universe@wsu.edu or read more at AskDrUniverse.wsu.edu.

How many colors can we see? –Andrew P., 12

Dear Andrew,

The human eye can see millions and millions of colors. But believe it or not, some colors exist in our world that the human eye can’t see.

That’s what I found out when I went to visit my friend Rachna Narula, an optometrist at the Washington State University Vision Clinic. Using a special camera in her office, she took a picture of my retina, the part in the back of the eye that helps us see color.

Seeing color requires light, she said. When light comes into the eye, it travels to the retina, bounces around, and triggers certain nerves. This sends a signal to your brain. The brain helps translate this signal into an image. In fact, the brain actually plays a big part in how we see color. When you were a baby, your brain was still developing and so was your color vision, Narula said.

Narula explained that humans don’t typically develop full color vision until they are about half a year or so old. Scientists generally agree that babies can only see about eight inches in front of their faces. It’s a pretty blurry view, too. Babies’ eyes are more likely to pick up on black, white, and shades of grey, rather than colors.

But as the brain and eyes develop, they start to pick up on more color differences. The retina in the back of your eye has millions of tiny parts called cones. There are three kinds of cones typically found in the human eye: red, blue, and green.

It’s these three kinds of cones that work together and allow you to see millions of colors. If a person is missing one kind of cone or all of these kinds, they might have a kind of colorblindness. Scientists also think there might be a fourth kind of cone, Narula added. But they are still investigating to find out for sure.

Of course, we can’t know exactly what colors babies or other animals see because they can’t tell us. Instead, we can use what we know about the eye and cones to put together an idea of how it all works.

We cats have red, blue, and green kinds of cones, too. Dogs have only two kinds: one for blue and one for yellow. The mantis shrimp, with their rainbow-patterned exoskeletons, have 16 kinds of cones. This particular shrimp can even see certain kinds of ultraviolet light that humans can’t see. Different kinds and numbers of cones can give animals vastly different experiences of how they see the world.

After all, even a single color can change depending on the lighting, shadows, or environment. Who knows—maybe one day you’ll invent a color counting machine and we’ll be able to get an even better estimate of how many colors exist. In the meantime, pull out the crayons or mix some paint. Dr. Narula and I would love to see what colorful things you can create. Send a picture to Dr.Universe@wsu.edu for a chance to have it featured with this column on AskDrUniverse.wsu.edu.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your question to Dr.Universe@wsu.edu.

Why do we hear the sea in a seashell? -Steve, Minnewaska School, Minnesota

Dear Steve,

Whenever us cats go to the beach, we tend to keep a safe distance from the water and like to explore the shore. I once stumbled upon a big, beautiful pink and white seashell.

When I put my ear up to it, I heard the familiar sound of whooshing waves. While there wasn’t actually an ocean inside, I figured the sound had to be coming from somewhere. So, I decided to investigate. You can try it out, too.

First, close your eyes and listen without a shell. Well, I suppose you are interested in reading this so you may not want to close your eyes, but definitely take a listen.

Perhaps you hear people talking, music playing, or a cat meowing. These sounds travel as waves from their sources at 761 miles per hour. When the waves reach your ears, they make your eardrums vibrate, and you can hear the sounds.

Just like a ball, these sound waves can bounce. A shell has a hard and curved surface. It is pretty good at reflecting, or bouncing the sounds around.

That’s what I found out from my friend Allison Coffin, a scientist at Washington State University. Her research helps people who experience hearing loss.

“When we hold a seashell up to our ear, we don’t actually hear the sea,” she said. “What we hear is normal sound from the environment we are in at the time—whether that’s your bedroom or the beach.”

As the sound waves bounce around inside the shell, they get a bit distorted, Coffin adds. A shell is a good kind of resonating device as air vibrates through it’s hollow inside.

It’s similar to the phenomenon of blowing across an empty glass bottle to make a whirring sound. Scientists can use their knowledge of how sounds move through different spaces as they engineer car engines, create musical instruments, and even reduce noise in planes.

You can find out more about how this distorted sound works by playing with some sound waves. Grab a shell, a cup, a mug, or even a toilet paper tube. You can also just place your hand around your ear and cup the end with your other hand.

Put one of these listening devices up to your ear and walk into rooms with different sounds. Listen to how the sounds in the shell change as you move from room to room. You might even try it out in a quiet room to hear what happens.

If you already happen to be standing on the beach, then you might just pick up on the sounds of the actual sea. After all, when you hear the sound of the sea in a shell, you are really hearing a combination of all the sounds around you at that very moment.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your question to Dr. Universe at AskDrUniverse.wsu.edu.

How do plants hold dirt? –Gordon, Pullman, WA

Dear Gordon,

The other day, I wandered into a Washington State University greenhouse and ran into my friend Mechthild Tegeder, a professor and expert on plants.

She gently dug a small plant out of a pot so we could take a closer look. When she lifted it up, I pawed at the clumpy soil hanging from the bottom to reveal some stringy roots.

“They’re amazing, aren’t they?” Tegeder said. “The root system functions like a web, anchoring the plant and the soil.”

The plant had lots of short, fine roots growing near the surface. Tegeder explained that another kind of root is a taproot and it tends to grow straight down. You have eaten one of these before if you’ve ever had a carrot.

While some roots grow near the surface, other roots make a journey deeper into the Earth. In fact, scientists have found roots nearly 200 feet below the surface of huge trees.

These roots can grow wide, too. Like the underwater part of an iceberg, a plant’s underground web of roots can take up to about four times as much space as the plant itself.

Whether you look at the roots of a giant tree, a little dandelion, or a carrot, they each have a couple things in common. As you know, they anchor plants to the soil. But they also deliver water and nutrients, or food, to the above-ground part of the plant.

Plants actually do this using really tiny hairs that sprout out of their roots. These little root hairs absorb the water and nutrients from the dirt. They deliver them up the roots, to the stem, and the rest of the plant or tree.

And roots look for these important resources anywhere they can. That’s part of the reason they will grow out in different directions.

In fact, there is even a special part of these hairs that scientists believe helps the roots sense where they are going in the soil. It’s a bit like an obstacle course, or like using your hands to navigate through a dark room.

These roots will grow in any space they can find. For small plants, this might mean empty space between clumps of soil. For big trees, it might mean roots that start to grow up and over sidewalks or walls.

Not all roots grow down or underground, though. Roots can grow up and out of the soil to reach into the air for nutrients and water. Then there are plants that don’t have roots at all.

But roots are really helpful to plants that do use them. As the roots and soil hang onto each other, they keep the important top layer of soil—the part we use to grow food—from washing away in the rain or blowing away in strong winds. Roots don’t just help the plant, but also the soil itself.

As you can see, it really just takes a bit of digging to get to the bottom of it. Keep asking great science questions.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your own question to Dr.Universe@wsu.edu or vote in this week’s reader poll at askDrUniverse.wsu.edu.

What is the smallest insect on Earth? –Laurenz, 8, Molino, Philippines

Dear Laurenz,

When I saw your question, I set out to explore with my bug net and a magnifying glass. I was searching all around for tiny insects when I ran into my friend Laura Lavine, a Washington State University scientist who studies bugs.

She said there are nearly a million different kinds of insects on Earth. The smallest of all the known ones are called fairyflies.

Like all insects, fairyflies have six legs. And like most insects, they also have wings. Some swim under water and use their wings as paddles. Their wings are also a bit hairy. It also turns out the fairyfly isn’t truly a fly. It’s a kind of wasp.

“They are almost impossible to spot with the naked eye,” Lavine said.

In fact, fairy flies are nearly 400 times smaller than the typical ant. And they are about two or three times the width of a human hair.

I imagine finding a fairyfly would be like finding a needle in a haystack. You’d have to keep a sharp eye out.

I started to wonder how exactly entomologists could spot such fairyflies or other kinds of small insects in the wild. For example, a couple years ago scientists discovered a new kind of fairyfly in Costa Rica. It was named Tinkerbella nana after the fairy from Peter Pan.

Lavine explained that scientists often use nets or traps to catch the insects. Sometimes they have to sift through dirt and litter, or decaying leaf matter, a teaspoon at a time to see what they can find.

Scientists can also use what they know about the insect’s behavior and habitat to help track them down. Fairyflies, despite their cute name, are killer insects. They lay eggs inside a host insect’s egg. When the fairyfly’s egg hatches, it eats the host egg. If we keep our eyes out for their host bugs and their eggs, we might also find the fairyfly.

Fairyflies are important for the environment, Lavine added. Farmers and scientists can use fairyflies to help get rid of bigger insects that damage grape vines, blackberries and sugar cane. These tiny creatures help us do a big job.

The insect world is filled with interesting critters. Thinking about the smallest insect also made me wonder about the biggest one on our planet. The biggest bug is a giant walking stick. It’s almost 2 feet long. But who knows? There might be even bigger insects or even smaller insects we haven’t discovered yet crawling around on our planet.

Thanks for your question, Laurenz. It reminds me that even the small things can inspire us to wonder big.

Sincerely,
Dr. Universe
Ask Dr. Universe is a science-education project from Washington State University. Send your question to Dr.Universe@wsu.edu

Why do we feel pain? -Sara, 11, Moscow, Idaho
Dear Sara,

Pain is unpleasant, but we need it for survival. Just the other day I was out exploring when I stubbed my paw and let out a big meow. My nervous system was doing its job.

Part of the reason we feel pain is because our bodies have tons of nerves that help us move, think, and feel in all kinds of ways.

When you stub your paw or toe, for example, the nerves in the skin of your toe will send a message to your brain that you are in pain. These messages are what scientists call impulses. They start in your toe, move to your spinal cord, then your brainstem, and onto your brain.

It’s actually your brain that tells you that you’re in pain. And if you’ve ever stubbed your toe, you know this message gets delivered pretty fast. In fact, when you feel pain, sometimes the impulse, or message, will travel at 250 mph. That’s the speed of a very fast racecar.

It’s important for the message to move fast because you have to make a quick decision about what to do. Sometimes your decision might be a matter of survival—but other times it might be as simple as deciding if you need a bandage, ice pack, or even a trip to the doctor.

Pain is actually the number one reason people see a doctor, said my friend Raymond Quock. He’s a scientist here at Washington State University who is really curious about pain.

“Pain in many aspects is good,” Quock said. “It’s a warning that your body is in danger.”
Most humans can feel pain, but not all humans, he said. Because of genetics or nerve injury, some people can’t feel pain.

Imagine touching a hot pan and not realizing it just came out of the oven. Or imagine if you broke your leg, but didn’t know it. And while that might sound pretty nice, it can also be quite dangerous.

If you didn’t feel pain, you might end up with even more damage to your body. Pain helps tell us when to take extra care of ourselves.
People have different kinds of pain, too. There’s physical pain, emotional pain—even growing pains. The kind of pain Quock studies is called chronic pain. Unlike acute pain, like stubbing your toe, chronic pain is pain that hurts and aches for months or longer.

This kind of pain doesn’t appear to have a very useful purpose. It doesn’t help much with survival. Quock and his team of WSU researchers are investigating why it happens and how to treat it. They are working on some great ideas about how to help patients feel better.

While some pain doesn’t seem to have a purpose, pain definitely does keep us safe in a lot of other potentially dangerous situations. Our nerves help us sense the world around us so we can explore. They can also help remind us to watch where we step next time.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your question to Dr. Universe at AskDrUniverse.wsu.edu.

Why don’t plants get sunburns? – Elijah, 5, Seattle, Wash.

Dear Elijah,

That’s a great observation. For as much time as plants spend outside in the sun, we really don’t see too many with a sunburn.

I decided to take your burning question to my friend Cynthia Gleason. She’s a plant scientist at Washington State University and knows a lot about plant defense.

Plants actually make their own kind of sun block, she said. It helps protect them from the sun’s intense ultraviolet rays.

We can’t see ultraviolet light, but we think bees can see it. This light helps bees find flowers so they can pollinate the plants and drink their nectar. Ultraviolet light might be useful for buzzing bees, but too much ultraviolet light can do some serious damage to plants.

“Unlike humans, plants can’t just move into the shade or put on a hat when the sun gets too intense,” Gleason explained. “Of course, plants also can’t slather on sunscreen.”

As you may remember from last week’s question, plants need sun to make their own food, as well as the oxygen we all breathe.

Plants face an interesting challenge because they need sun, Gleason said, but not too much sun. Otherwise, they might shrivel up, turn yellow, or even die.

For a long time, scientists weren’t really sure how plants avoided getting burnt to a crisp. But a few years ago, a group of researchers investigated a science question very similar to yours.

They found that when plants get too stressed out from the sun, they start to make their own kind of sun block. It isn’t like the sunscreen that humans squeeze out of a bottle or spray on. But like sunscreen humans use, it blocks the ultraviolet light.

The plant’s sun block is actually a combination of special molecules that form in the plant’s tissue. These molecules join together to create a compound that blocks the ultraviolet light. But at the same time, these compounds still allow other kinds of sunlight to pass through. That way, the plant can still make its own food—without turning into a lobster.

Plants aren’t the only living things that make their own concoction of chemicals to stay safe in the sun either. Some zebra fish create a compound that protects them from the sun, too. Even hippos make a kind of orange sweat that helps protect them from ultraviolet rays.

The sun is not only good for plants, but also for us. It gives us Vitamin D that our bodies use to help our bones stay strong. Thankfully for humans, chemists have invented sunscreen to keep you safe from the sun’s rays while exploring outside. And luckily for us cats and other critters, we can usually find a nice shady tree.

Sincerely,
Dr. Universe
Ask Dr. Universe is a science-education project from Washington State University. Send your question to Dr.Universe@wsu.edu or read more at AskDrUniverse.wsu.edu.

Why does onion cause you to cry? –Kera, 5, Lawrenceville, GA

Dear Kera,

Try as we might, it’s hard to hold back tears while chopping up onions.

My friend Lindsey du Toit knows the feeling. She’s a scientist at Washington State University and works with lots of onions. Her research helps farmers grow good vegetables for us to eat.

“It’s not the onion itself that makes us cry,” she explained, “but a chemical reaction that starts when you cut into it.”

I wondered how exactly this chemical reaction worked. To find out, we set up a microscope in her lab and chopped up a Walla Walla sweet onion. I wiped a few tears from my cheek and slid a tiny piece of onion under the lens.

Under the microscope’s light, we could see rows of onion cells next to each other. Just like you and me, onions are made up of cells.

An onion sitting on the kitchen counter is pretty harmless because its cells are still together. But when we cut up an onion, we also cut up a bunch of the cells. This is where the chemical reaction begins.

Cutting the onion breaks open different parts in the cell and releases chemicals into the air. Some of these important chemicals contain sulfur.

“As the plants grow, they take up sulfur from the soil,” du Toit said. “It’s good for growing onions.”

This sulfur is important for the flavor, too. But some of the chemicals in onions that contain the sulfur also have the side effect of making us cry.

“It’s a sacrifice we pay for good-flavored onions,” du Toit adds.

The onion cells also contain parts called enzymes. It is the job of these enzymes to help chemical reactions happen. In the onion, the enzymes help convert the sulfur into a kind of acid.

This acid rearranges itself to form a new kind of chemical: syn-propanethial-S-oxide. It’s a bit of a tongue twister. It’s also a tearjerker.

When the chemical drifts up and meets the moisture in our eyeballs, it turns to sulfuric acid. Our eyes have many nerves and can sense that something unusual is happening—and that something is stinging.

Tear-producing glands in our eyes, called lachrymal glands, receive the message.

du Toit explained that an onion with more sulfur is often likely to produce more tears. For example, Walla Walla sweets are sweeter and don’t take up as much sulfur from the soil. They likely won’t provoke as many tears as some other onions might.

People have tried quite a few techniques to try to avoid crying when they chop onions. Some put onions in the fridge before cutting them to slow the chemical reaction. Others cut their onions under cold water to slow the chemical reactions with the sulfur compounds.

Chemical reactions often happen more slowly in cold conditions. So the idea is that cooling onions in the fridge before cutting them means that the sulfur chemicals are converted more slowly into the acid that reacts with your eyes —helping you chop more onions and slowing the waterworks.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your question to Dr. Universe at askDrUniverse.wsu.edu.

What is the deepest spot in the ocean? -Lawrence, 11, Philippines 

Dear Lawrence,

Deep underwater, not too far from Guam, lies a crescent-shaped canyon called the Mariana Trench. It is home to the deepest known spot in the ocean: The Challenger Deep.

That’s what I found out from my friend Ray Lee. He teaches biology at Washington State University and studies animals that live in the deep sea.

A few explorers have made the nearly seven-mile journey to the Challenger Deep. Even though us cats aren’t big fans of water, I can imagine what it would be like to go there. We would have to go in a specially designed underwater vehicle, and we’d go through several different ocean zones along the way.

First, we’d pass through the Sunlight Zone. These are the brightest waters and we might see some fish, turtles, jellyfish, or stingrays swimming along.

We’d then pass through a part of the ocean called the Twilight Zone. Everything around us would start to get darker and darker. We might even see some critters making their own light, or bioluminescence, in the dark.

Next we’d pass through a part of the ocean called the Abyssal Zone. No sunlight would be able to reach us here. There would be no plants. The living conditions would be extreme, too. We might see extremely hot water from deep in the Earth erupting from chimney-like vents.

Lee is really curious about these vents and the creatures that are able to live in such extreme conditions. One of his favorite parts of his job is building instruments and devices that help us investigate these kinds of deep-sea environments.

The ocean can be a tricky place to study. It’s not only really dark, but the deeper you go, the greater the pressure of water pushing down on you. But Lee likes the challenge of exploring the mysterious deep.

“We are always interested in the unknown,” Lee said. “And the ocean has perhaps more things that are unknown than any other environment.”

Even deeper than the Abyssal zone is the Hadal Zone. This is where we find deep ocean trenches—and the Challenger Deep. I found out it wasn’t until pretty recently that scientists were able to go explore it.

James Cameron, an explorer and filmmaker known for “Titanic” and “Avatar,” piloted a one-man trip down to the Challenger Deep a few years ago. Before that, oceanographers Jaques Piccard and Don Walsh went to investigate.

They had to use special vehicles and equipment to reach these deep waters. Scientists have even set up underwater cameras that help us look at what life is like there. In the Hadal Zone, there are big mountains rising from the floor and possibly more sea vents. Scientists are learning about some of the creatures like sea cucumbers and really small crustaceans that call this part of our world home.

There is so much more to explore, Lawrence. Maybe one day, you’ll help us discover even more about our deep, vast oceans.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your question to Dr.Universe@wsu.edu or vote in this week’s reader poll at AskDrUniverse.wsu.edu.

How is ice cream made? –Israel, 7

Dear Israel,

It just so happens that July is National Ice Cream Month. To celebrate, I decided to whip up some homemade ice cream. You can try it at home, too.

Put milk, sugar, and vanilla into a freezer bag and seal it up tight. Fill another gallon freezer bag with ice and rock salt. Place the liquid mix bag inside the ice bag and give it a good long shake. Some scientists might call this part “agitating.” After five minutes or so, you’ll notice the liquid mix in your bag becomes solid. Then you can dig in with a spoon. Find all the instructions for Ice Cream-in-a-Bag at AskDrUniverse.wsu.edu.

After making my own homemade tuna-flavored ice cream, I decided to take a trip to the Washington State University Creamery to see how the professionals make ice cream for Ferdinand’s Ice Cream Shoppe.

I met up with our friend John Haugen, the creamery manager. Each year at the WSU creamery, students make more than 18,000 gallons of ice cream. That’s a lot of scoops.

Just like our Ice Cream-in-a-Bag recipe, their recipe uses a mix of milk, cream, and sugar that’s frozen in a way to prevent crystals from forming and incorporates enough air to make it soft. At the creamery, milk flows through pipes into big stainless steel tanks that have been specially engineered.

The students add a bit of fat to the mix in the form of cream, which gives the ice cream a smooth texture. When the fat mixes with air, it helps create small pockets in the ice cream. It makes the texture smoother. In fact, a scoop of ice cream is about half air.

When making ice cream, we need to keep the ingredients blended together. With all the liquids going in the vat, we also add a few solids like dry milk, followed by the sugar. Then, we heat it up to 155 degrees to pasteurize the milk and kill any bad bacteria that might have snuck into the mix.

We also don’t want the cream to rise to the top or different parts to separate. This is where we add in what’s called an emulsifier. One of the original emulsifiers that did the trick was actually egg.

We also want to keep the ice cream from getting too many ice crystals. So, we add in a bit of carrageenan, a kind of seaweed. But it’s just a tiny bit. It helps keep the ice cream from forming those tiny ice crystals.

The liquid goes through a homogenizer, forcing the mix through a small opening and breaking down milk fats into smaller pieces to make the ice cream even smoother.

Finally, the mix goes through a specially engineered machine to bring the temperature down. Then it gets sent through a freezing barrel and packed into boxes until it’s ready to eat. The best part of the job is eating the ice cream, Haugen adds.

Sometimes there’s no better way to find out how something is made than to give it a try. Tell me about your ice cream experiments sometime at Dr.Universe@wsu.edu.

Sincerely,
Dr. Universe

Ask Dr. Universe is a science-education project from Washington State University. Send your question to Dr.Universe@wsu.edu.

Why does soda fizz? –Emily, 9, Florida

Dear Emily,

If you’ve ever had flat soda, you know a sip isn’t the same without some fizzy bubbles. We can hear them pop and feel them burst on our tongue.

I wondered if there was some secret ingredient that made soda bubbly. My friend Kenny McMahon, who researches food science here at Washington State University, and I decided to investigate.

We grabbed a balloon, a bottle of soda, and salt. We filled the balloon with about a teaspoon of salt. Then, we twisted the cap off the bottle and stretched the balloon over it’s top. When the balloon was secure, we tipped in the salt.

Right before our eyes, the balloon started to inflate. I was tempted to pop it with my claws, but resisted.

The salt caused the soda to produce carbon dioxide gas. This was no surprise to McMahon. His research is all about the bubbles and fizziness made from carbon dioxide gas.

You may be familiar with this gas, too. It’s the one we all breathe out and plants use to make food. It’s also what makes the bubbles in soda—and makes us burp when we drink it.

At soda bottling plants, carbon dioxide from tanks is pumped into the liquid, where it dissolves and later forms bubbles.

Liquids like soda can change under different temperatures and pressures. Liquid at a higher temperature can hold more sugar in a solution, for example. And liquid at a higher pressure can hold more gas in a solution.

A whole bunch of gas gets crammed into a pretty small space and creates a lot of pressure inside a soda can.
There probably wouldn’t be a whole lot of bubbles in the can since the gas is in equilibrium—a balance between gas dissolved in the liquid and the gas in the space at the top of the can.

But when you open the can, the pressure lowers and the gas escapes. You can actually hear this happening as the soda fizzes. Bubbles quickly form in the liquid, rise to the surface, and pop to release carbon dioxide into the air.

The carbon dioxide can escape in all different directions. And of course some of it lands on the tongue’s taste bud receptors when you sip your soda.

Your brain translates this into “fizziness” and it just might make your face twinge.

Soda isn’t the only place we find carbonation, though. We can also find it in nature.

While researching your question, I stumbled upon a group of carbonated springs in Idaho. They are fittingly named, Soda Springs. Just like in a can of soda, there’s a lot of pressure in the ground beneath the springs. The carbonation originates from natural reactions deep within the Earth.

Science is all around us. McMahon has a few things for you to keep in mind as you continue to explore.

“Remain observant,” he said. “Keep asking questions and don’t let anyone burst your bubble.”

Sincerely,
Dr. Universe

What do you call soft drinks? Soda? Pop? Cola? Vote in the reader poll at askDrUniverse.wsu.edu.

Why is there iron in my cereal? Is there iron in other food? –Phillip, 11, Pullman, WA

Dear Phillip,

Iron is found in buildings and skyscrapers. It makes up most of the Earth’s core. It’s even found in the Sun and stars. And yes, it’s also in a bowl of cereal.

In nature, we might find iron in a black and steely mineral form buried deep in the earth. But right in our bodies, we also find iron in blood.

That’s what I found out from my friend Brennan Smith when we set out to investigate why there’s iron in cereal and other foods.

Smith is a professor of food science who teaches students at Washington State University and the University of Idaho. He explained that iron is in cereal and other foods for our nutrition. I wondered exactly what it does for us.

Smith explained that in your blood you have something called hemoglobin, which gives your blood its red color. Hemoglobin also helps carry oxygen through your body. But it can’t do this without the help of iron.

Iron helps bind the oxygen you breathe to the hemoglobin. The hemoglobin holds onto the oxygen and carries it through your body to help you stay strong.

“That’s one of the most important reasons why we have iron,” Smith said.

Without iron, you might start feeling weak and tired because your body isn’t getting enough oxygen. But eating foods with the right amount of iron helps you grow, think, and play.

My friend Jen Hey, another expert in nutrition here at WSU, said good sources of iron are eggs, beans, some kinds of shellfish, and meat. Mmm, I was starting to get hungry. There’s also iron in tofu, dried fruit, and dark, leafy green vegetables.

The plants farmers grow to make cereal grains also need iron, too. These plants use iron to help carry oxygen, just like in people. And without iron, they wouldn’t be able to make their green colors.

A lot of plants and animals naturally have a lot of iron. Sometimes there are foods that are fortified, and iron is added to give it a boost.

It depends on what kind of cereal you are eating, but usually there is a small amount of iron combined with other ingredients. Just read the label and you’ll find out about things like zinc, calcium, and vitamins.

From the stars in outer space to plants in a field to the cereal in your bowl, iron is an important element in our universe. Iron is a kind of metal. Metals can also be magnetic. Iron is magnetic, too. That’s why you can grind up some cereals and get the iron out with a magnet.

There might even be some iron in the metal spoon you use to eat your cereal in the morning.

If you like food and science, perhaps you might want to be a food scientist one day, Phillip. In fact, with a question like this one, you are well on your way.

“Keep asking lots of questions,” Smith said. “Always be asking questions.”

Sincerely,
Dr. Universe

Tell us about the science in your breakfast! Vote in our new weekly reader poll at http://askDrUniverse.wsu.edu.

Do we drink the same water dinosaurs drank? –Sophia, 7

Dear Sophia,

Yes. The water on our Earth today is the same water that’s been here for nearly 5 billion years. Only a tiny bit of it has escaped out into space. As far as we know, new water hasn’t formed either.

That means there’s a very high chance the water in your glass is what thirsty dinosaurs were gulping about 65 million years ago.

It’s possible that you could drink the same water as a stegosaurus or a T-Rex because of the way water circulates around our planet. A dinosaur, you and I are actually part of this water cycle, too.

As water on the surface of lakes, oceans, and rivers warms up, it travels into the sky as very tiny droplets, or vapor. When the water vapor gets colder, it turns back to liquid to help form clouds.

When the liquid gets so heavy it can’t stay in the atmosphere anymore, it falls, or “precipitates,” as rain, snow, sleet, hail, or, my favorite, graupel. Once the precipitation reaches the ground or lands in lakes, oceans, and rivers, the cycle continues.

You, a dinosaur, and I drink water, and eat foods that contain this water, too. It’s so refreshing to lap it up from my bowl. We get rid of some water as fluids or gases, such as the ones we let out when we breathe.

That’s what I found out from my friend Kent Keller who investigates the water beneath Earth’s surface. He’s a geologist with Washington State University’s School of the Environment.

He said water also moves in ways we don’t always think about. Scientists have found water trapped in minerals deep within the Earth’s mantle and crust, he explained. This water is even older than dinosaurs. It doesn’t look like liquid water that’s in your glass, but it still made of the same stuff.

“We’ve realized there is a lot of water down there,” Keller said. “There’s as much water chemically speaking, more or less, as there is in the oceans. It’s just in a different form.”

Another place we find water from dinosaur days is in organic matter. When the dinosaurs died, their bodies broke down to become part of the Earth. Over time, some of this organic matter became shale, coal, and oil we use for fuel.

The water dinosaurs drank is in more than just the water we drink, minerals, and organic matter. It’s also what we use to shower, cook, and water plants for food.

Right now, Keller is visiting with fellow scientists at the Global Institute for Water Security in Saskatchewan, Canada. They are curious about how we’ll take care of our water for the future.

“Life as we know it – every cell in every plant and animal — is mostly water. To say it requires water is an understatement,” Keller said.

The water in your glass may be the same water dinosaurs drank, but it’s also the same water that’s going to keep life on our planet in the years to come.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

Why is the ocean salty? –Alysin, 10, Ruston, La.

Dear Alysin,

At first, I thought the answer to your question might take us deep into the ocean. But it turns out the source of our salty seas is actually on land.

My friend Professor Steve Katz and I took a walk along the shore of a nearby river to investigate.

Katz is an environmental scientist here at Washington State University. He pointed out some big rocks along the river. That’s where the salt comes from, he explained. Yep, it all starts with rocks and dirt.

Rocks contain minerals, such as salts. A lot of it is the same kind of salt you might sprinkle on food: sodium chloride. As you might guess from its name, the salt is made up of sodium and chloride atoms. There are other kinds of salts made up of different atoms, too. And water is really great at dissolving them.

You can actually watch this happen just by adding a little salt to a cup of water and mixing it with a spoon.

As the salt’s sodium and chloride atoms break apart from each other in the water, the grains of salt disappear. The chemical reaction in the water has pulled the different parts of salt away from each other.

Likewise, the water in streams and rivers is really good at helping dissolve the salts from rocks, too. The salt travels through the streams and rivers into the oceans. When the water from our ocean evaporates to become clouds, the salt is left behind. There’s literally tons of it, too.

According to the National Ocean Service, if we took all the salt from the oceans and spread it around the Earth’s surface, it would form a pile nearly 500 feet high.

Katz explained that oceans weren’t quite as salty in their early days as they are today. But once the oceans got saltier they stayed that way, more or less, for nearly 4 billion years.

Not all the salt stays in the ocean. And the faster salt enters the ocean, the faster it leaves.

Salt comes in from places like rivers and streams, and once it reaches the ocean it goes into other places besides the water.

“The salt goes into a bunch of places,” Katz said. “It goes back into the soils. It gets taken up by critters.”

Ocean animals are well equipped for their saltwater home. Fish can pump out extra salt through their kidneys and special cells in their gills. Even birds that live near the ocean, like albatrosses or seagulls, can drink seawater and process the salt using special glands behind their eye sockets.

Salt also ends up at bottom of the sea. Salt that sinks to the bottom can form into rocks made out of sodium chloride or sodium sulfates.

But no matter where the salt goes, one thing is for sure: We can count on the ocean to be just about as salty tomorrow as it was today.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

Why do we get brain freezes? –Hannah, 9, Monroe Elementary

Dear Hannah,

You’re enjoying some ice cream, when suddenly you feel a pain in your head that hurts a whole lot. It’s like it came out of nowhere, and in a matter of seconds, it’s gone.

These instant headaches, or brain freezes, often strike when we eat or drink something cold. And like you, some scientists are curious about why brain freezes happen. So they’re testing out some different ideas.

That’s what I found out from my friend Bill Griesar, a brain scientist at Washington State University.

One theory is that when you eat or drink something cold, it triggers a change in the blood vessels lining your mouth and throat.

Blood vessels are like little tubes carrying blood to the brain. A change in temperature can make these blood vessels grow wider.

“So you get this super painful rise and intense headache-y kind of feeling,” Griesar said. “The nice thing about ice cream headaches, is, very quickly, the vessels constrict. They go back to their normal size.”

As you experience a change in your blood vessels, it may set off other events in in your brain and body.

Griesar said brain freezes might be connected to an important nerve in your face. Our nerves help us move, think, and feel in all kinds of ways.

It just so happens Griesar and his students are learning about one nerve that helps the brain and face communicate: the trigeminal nerve.

The nerve stretches out across your face in three branches.

“One goes to a part of your mouth, one goes below your mouth, one goes around your eyes,” Griesar said.

Along these branches there are clumps of neurons called ganglia that help carry information from your face to your central nervous system.

Nerves and ganglia can help different parts of your head and body communicate. Because it stretches across your face, the trigeminal nerve might be why you can feel an ice cream headache in your eyes or nose, too.

The narrowing and widening blood vessels appear to put a lot of pressure on ganglia near the trigeminal nerve. The trigeminal nerve sends a message to the brain that you are in pain.

It may feel like the brain freeze is inside the brain, but it’s likely being experienced as pain in the face, and the meninges, which are layers of tissue, with pain-sensing neurons, surrounding the brain.

Nerves often communicate pain to warn us of something dangerous. But the pain from brain freezes doesn’t appear to be harmful.

We’ve still got more investigating to do when it comes to why exactly we get brain freezes. I think I’ll go do an experiment of my own at Ferdinand’s Ice Cream Shoppe. Here at Washington State University, they make my favorite ice cream. I’ll have to eat a bunch of it—in the name of research of course.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Tell her about your favorite ice cream. Ask Dr. Universe is a science-education project from Washington State University.

Why do we age? –Logan, 12, Pullman, WA

Dear Logan,

It’s usually later in life that we see the more dramatic signs of aging, like gray hair, wrinkles, and lots of birthday candles on our cake. But we really start growing older from the time we are born.

The way humans change across the lifespan fascinates my friend Cory Bolkan, an associate professor of human development here at Washington State University.

“There isn’t really one factor, one theory, or one line of research that can explain aging,” Bolkan said. “It’s kind of an exciting area with lots of opportunities to explore.”

For example, some scientists are really curious about how people age in space versus here on Earth.

NASA astronaut Scott Kelly recently returned from a year-long mission aboard the International Space Station. Scientists are curious if conditions of space, like living in weak gravity or being around particular particles from outside the solar system, might change the way a person ages.

They are also interested in the things we can’t always see right away.

Scientists think part of the answer to your question may lie in our genes. So, they want to look at Scott’s DNA.

“Our genes contain information about us that’s been passed down from our parents, grandparents, and ancestors,” Bolkan said. They hold the instructions for hair color and skin color, for example.

Scientists are particularly interested in studying Scott because he also has an identical twin brother. That means they were born with DNA that is exactly the same. Scientists will zoom into the ends of their DNA and observe sections that we think might be linked to growing older.

But it’s not just our genes that play a part in why we age, Bolkan said.

“You can have two identical twins who share the exact same DNA,” Bolkan said. “You can look at them again decades later and you’ll see that genetically they are more different.”

She said this makes the answer to your question even more complex. Our environments interact with our genes, too.

There are certain things in our environment that can damage our genes. The damage can be a result of activities like smoking or not wearing sunscreen. This kind of activity can speed-up the aging process, Bolkan said. Our physical appearance changes as a result of “wear and tear” on our DNA.

While we haven’t pinpointed the exact answer to why we age, we are finding clearer answers to other questions about growing older.

For example, the power of our mind can change the way we age, Bolkan said. Studies have shown people with a positive outlook on aging actually tend to live longer.

“People say ‘I don’t want to get older, it doesn’t look like fun’,” Bolkan said. “But when you look at the research and you look at happiness, we are the happiest later in life.”

Perhaps some of your best birthdays will be the ones with the most candles on your cake.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

Why do we have earwax? –David, 10, Albany, Oregon

Dear David,

The other day I was scratching my ears when I noticed some yellowish-brown gunk on my claw. It was pretty gross, but it also made me very curious.

I decided to meet up with my friend Susan Perkins and investigate why we have earwax.

Before Perkins was a nursing instructor here at Washington State University, she spent several years as a school nurse. She’s seen some big clumps of earwax.

We have earwax for many of the same reasons we have mucus in our nose, she said. You may remember that Perkins helped us explore our questions about boogers not too long ago.

Earwax helps keep invaders like bacteria and dirt from getting deep into our ears.

“It’s really that simple,” she said. Still, having earwax at all is especially important for protecting our inner ears, which connect with important nerves for balance and hearing.

And while earwax does pretty much the same job for all of us, not everyone’s earwax is alike.

“People make different kinds of earwax,” Perkins said. “Some people make a kind of crusty earwax and other people might make kind of wet, juicy earwax. Isn’t that fun? Kids usually have juicier earwax than adults.”

The outer ear is the earwax factory. It’s where special glands under your skin produce the sticky, wet wax. Technically, it’s called cerumen (suh-ROO-men).

“It’s mostly long chains of fats, but there’s cholesterol in there, and there’s also a little bit of alcohol,” Perkins said.

As you move your jaw, the earwax slowly travels deeper into the inner ear to do its job.

Humans and cats aren’t the only animals that have earwax.

A couple years ago, scientists found a ten-inch-long piece of earwax in a blue whale. That seems huge to a human or a cat, but to a nearly 80-foot-long blue whale, it’s not too unusual.

The scientists investigated chemicals in the earwax to learn more about whales’ lives. For example, the earwax provides clues about where the whales were swimming and pollution in the water.

It makes me wonder what earwax might tell us about humans.

In fact, some scientists have actually studied parts of human DNA that tell us if a person’s earwax will be crustier or juicier. Others have even baked little bits of earwax to find out about more about how it smells. They wonder if chemicals released from earwax may help them learn about other kinds of body odor. Yes, earwax can sometimes be a little stinky.

Which reminds me, Perkins said when it comes to keeping our ears fresh and clean, it’s best to just dab our ears with a towel after bathing. She also offered one final piece of advice: Don’t ever stick anything smaller than your elbow in your ear.

Sincerely,
Dr. Universe
Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

What is fire? -Anish P., 10, Nepal

Dear Anish,

There’s nothing like taking a little catnap by the fireplace, feeling the heat, watching the flames, and listening to crackling sounds. But until you asked, I wasn’t entirely sure what this mesmerizing thing was or how it works.

I decided to find out from my friend Michael Finnegan. He’s a chemistry professor here at Washington State University.

In the 4th grade Finnegan got a chemistry set that came with a chemistry book. He read about how everything around us is made up of building blocks called atoms. He learned how atoms get together to form molecules. And when different atoms and molecules come together, they can react in different ways.

“What fire really is, is a whole bunch of fragments of molecules that have way too much energy,” Finnegan said. “So they are emitting that energy in the form of heat and light. That’s what we actually see.”

The super-fast reaction that creates fire is called combustion. In order to make it happen, we need a few things.

First, we need a source of heat. This can be a spark, for example. It’s something to get different molecules in our reaction moving fast and energetically.

The fuel might be wax on your birthday candle or newspaper in a fireplace. These items are typically made up of molecules that contain carbon and hydrogen atoms.

“One of the first things to notice about fire, if you look at a candle or fire in the fireplace, is you’ll notice the flames never actually touch the fuel,” Finnegan said.

That’s because heat turns some of those molecules from the fuel into a gas we can’t see. So, it appears the flame is floating.
If all we had were fuel and heat, we’d only have this gas. The final ingredient we need to make fire is oxygen.

“The easiest way to think about it, is the source of heat, or energy is tearing molecules apart so they can combine with oxygen,” Finnegan said. “If you’ve ever taken anything apart, you know what a mess it can make.”

And to understand why oxygen is so important in the reaction, we need to know a little more about how atoms work, Finnegan said.

Atoms have particles called electrons. Most atoms want more electrons. They can often get them by sharing electrons with another atom. If an atom shares an electron it also gains an electron. This also helps molecules form new bonds, too.

Usually the two oxygen atoms that make up our air share electrons. But when the gas from fuel mixes with oxygen atoms in the air, they stop sharing. Instead, they start forming stronger bonds with hydrogen and carbon. These stronger bonds mean more energy. The energy vaporizes more fuel molecules to keep the fire going.

Electrons help give off both the light we see and heat we feel from a flame. The next time you are sitting around campfire, or you blow out your birthday candles, remember, it’s all chemistry.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

How are bones made? -Oscar, 10

Dear Oscar,

A couple months before you were born, your skeleton was soft and bendy. It was made out of cartilage, the same material that’s in your nose and ears now. But when certain cells in your body called osteoblasts and osteoclasts began to work together, new bone started to form.

In fact, you were born with about 300 tiny bones in your body. As you began to grow, some of the bones fused together and became single bones. Now, you carry around a skeleton of 206 bones.

Those bones are pretty strong, too. They are mostly made up of the same minerals that keep your teeth strong and a tiger’s claw sharp: calcium phosphate. They also contain some proteins, vitamins, water, and other elements.

That’s what I found out from my friend Susmita Bose. She’s a materials engineer here at Washington State University and knows a lot about the science of our bones.

As strong as our bones may be, they are actually breaking down all the time, she said.

“There is always a micro-crack that is generating in our musculoskeletal system,” Bose said. “Bone keeps repairing itself throughout our life.”

We have two main types of bone cells. There are the bone-eating cells called osteoclasts and the bone-building cells called osteoblasts. They work in a cycle. Since the day you were born, your skeleton system has been, in a way, always re-making itself.

Still, sometimes our bones do more than just micro-crack. Even when we do our best to keep our skeletal system healthy, bones sometimes break. As we get older, the bone-building cells start to slow down. Some bones can become so damaged that a person might need to replace them.

In the lab, Bose and her team use a special form of calcium phosphate to make custom bone replacement parts. These are called implants. It takes a group of smart scientists who know a lot about chemistry, biology, engineering, and medicine to make the implants work.

“You can make a special X-ray scan of the bone defect, then send a file of the information through a computer, and the 3-D printer will make the part based on your file,” Bose said.

She showed me a few of the bone replacement parts from the printer. They looked and felt a lot like the bones you’d find in the human body.

“I often say it isn’t easy to mimic Mother Nature,” Bose said. But using a variety of sciences, she said the team is getting closer to building bone materials that improve the way people heal.

They design implants that are friendly to the rest of the body and that get along with the different bone cells and other cells, so the growing cycle can continue.

Maybe someday if you break your arm in football or hurt your ankle in soccer, your doctor could pop in a specially made implant. Perhaps you would even be able to join your team again before the season ends.

#NationalEngineeringWeek begins Feb. 21! Tell us what engineering means to you! Send drawings & messages to Dr.Universe@wsu.edu. We might just feature it on the website.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

What are boogers? – Taryn, 9, Seattle, WA
What exactly is a booger and is it harmful to eat? – Concerned grandpa

Dear curious readers,

When I went to visit my friend Susan Perkins, an instructor of nursing at Washington State University, she shined a tiny light in my nose. Sure enough, she found some crusty little boogies.

Perkins said boogers actually start out in the nose as sticky, slimy mucus, which is mostly water. It also has a little protein to keep it sticky, some salt, and other chemicals.

“Many of our organs make mucus,” Perkins said. “It’s just that the kind in our nose turns into boogers.”

In your nose, tiny hair cells help push the mucus down toward your nostrils. Mucus dries out in the air and pretty soon you’ve got a booger. But not all mucus is destined to become a booger.

Some of the mucus from your nose goes in the other direction and gets flushed into your stomach. While that might sound gross at first, mucus plays an important part in protecting the human body. Mucus can grab onto invaders such as dust particles or bad germs. If any harmful germs do make it to your stomach, the stomach acids will probably destroy them.

Mucus from the nose lines your airways in a nice gooey layer to help protect your lungs.
“The reason we have mucus is because it helps capture and flush out any foreign particles that we breathe in,” Perkins said.

And between the mucus that forms in the nose, stomach, lungs, and guts, the body makes quite a bit of it, too.

Since the stuff that’s in our boogers is what you end up swallowing anyway, it’s left some scientists wondering if eating mucus might help boost the body’s defense system. Though, I imagine it might be tough for scientists to find humans who want to volunteer in the research to help find out.

It might sound absurd to eat mucus, but some organisms actually make a meal out of it. Tiny crustaceans called sea lice eat mucus that forms on salmon.

While sea lice like to eat mucus, eating boogers or mucus tends to gross people out. Your friends probably don’t want to see you doing it and you probably don’t want your friends to see you picking either.

And in the end, it’s the picking part that could cause trouble, Perkins said. Picking can irritate your nose. It might even cause a little bleeding, which could open you up to more germs or infection. Germs may also spread from your nose to your hands and to other people.

As I left Perkins’ office, one of my boogers was coming out of the cave. She kindly offered me a tissue. It’s usually best to use a tissue when you are handling the boogies.

The next time you blow your nose, that little crusty glob may just remind you that your body is working hard to keep you healthy.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

Why is pi 3.1415…? What if it was just 3? –Anonymous

Dear Curious Readers,

It’s almost March 14. You know what that means: Pi Day, as in 3/14, or 3.14159265359 and so on.

I met up with my friend Nathan Hamlin, a mathematician and instructor here at Washington State University, to explore your question about this never-ending number.

We calculated Pi with some of my favorite items: yarn and a tuna can. You can try it at home, too.

We cut a piece of yarn that was just long enough to go around the circumference of the tuna can. Next, we straightened the yarn out and measured it with a ruler.

Then, we took a piece of yarn and laid it across the top of the tuna can. That gave us its diameter.

Then we did some division. If you try this at home and are still working on your long division, you can use a calculator.

We took the circumference and divided it by the diameter. We tried our yarn measurements again with a plate and a clock. We had to be very precise, but every time we divided the numbers, we got the same answer: about 3.14.

“Pi is part of the nature of the circle,” Hamlin said. “If the ratio was different, it wouldn’t be a circle.”

So, that makes your second question a bit tricky. If Pi wasn’t 3.1415 and so on, circles wouldn’t exist as we know them today.

I also found out there was a mathematician in Indiana who was convinced Pi was actually 3.2. He even tried to make it a law so all the students in the state would have to use that number in their math classes. Of course, it didn’t pass.

Hamlin said if Pi really were 3.2 or 3, it would mean Pi was a rational number.

Rational numbers include fractions, counting numbers, negative numbers, numbers with decimals that end (ex: 3.0374), and numbers with decimals that repeat (ex: 0.33333).

“This kind of goes back to one of the things in the ancient world, which was when math was first developed,” Hamlin said. “People thought that the world was a more rational place than it was.”

People thought the universe—and math—would be more orderly or logical than it turned out.

“There’s a story that’s told by math teachers that when the Pythagoreans discovered there was an irrational number, they were all on a ship together,” Hamlin said. “The person who figured it out, well, they through him overboard!”

Pi is an irrational number. Unlike the rational numbers that have sections of repeating digits after the decimal, Pi’s digits look a little different. To give you an idea, here are just the first hundred digits of Pi: 3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679.

You can find Pi in nature, too. For example, you can find it in the pupil of our eyes or ringed splashes in ponds. Albert Einstein even found Pi in the shapes of rivers. It just so happens Pi Day falls on Einstein’s birthday, March 14. OK, he was born in 1879, not 1592.

I think I’ll celebrate math and science with a nice slice of tuna fish pie.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

Hi, Dr. Universe, Can you hear in space? -a curious reader

Dear curious reader,

Your question reminds me of an experiment: You put a ringing alarm clock in a jar and use a hose to slowly suck out all the air. As the air escapes, the ringing gets quieter until there’s no sound at all.

The inside of the jar becomes what scientists call a vacuum. It’s empty. Just like space.

Despite any zooms and explosions you may have heard in movies about outer space, sound actually can’t travel through empty space. That’s why on the moon, where there is no air, astronauts have to use radios to talk with each other.

But here on Earth, all kinds of sounds are traveling through air, water, and other objects. The molecules that make up these objects help the sound travel.

That’s what I found out when I visited my friend Allison Coffin to learn more about how sound moves. Coffin is a brain scientist here at Washington State University. In her research, she investigates hearing and hearing loss.

She explained that when you hear a sound, somewhere around you an object was moving, or vibrating. If you’ve ever strummed a rubber band you’ve probably heard, and maybe even seen, this at work.

The molecules that make up water or air sort of bump into each other as they vibrate. They pass on their motion to neighboring molecules.

While sound doesn’t travel through empty space, there are other places off our planet where scientists have detected sound waves. For example, some scientists have used different machines to pick up sound waves from gas clouds beyond our atmosphere.

“In general, the sounds are probably so low a frequency, a mega bass, that our ears can’t hear it,” Coffin said. “In fact, I don’t know of any animal on Earth that could hear sounds so low.”

Meanwhile, in Earth’s atmosphere, animals can hear a range of sounds. Sound that travels through air moves about 1,114 feet in a second. Underwater, sound moves about four times faster.

Coffin explained how sounds beneath Earth’s water tend to have a low frequency. The sounds travel a lot farther and reach their destination faster than high frequency sounds.

“Think about songs of baleen whales, like humpbacks and blue whales,” she adds. “Higher frequency sounds don’t travel as far because they bounce off things and get reflected back (by) things like corals, rocks, and boats.”

The songs of baleen whales can travel so far that some scientists have found that whales can hear each other from nearly a thousand miles away. That’s farther than the distance from Seattle to Los Angeles.

The next time you hear a sound, think about all of the molecules that helped carry it to your ears. Think about how far it traveled and what it traveled through. And remember, it’s quiet out there between the planets and stars.

You can try your own experiments in sound and explore other projects at pinterest.com/AskDrUniverse. Send a picture of your project to Dr.Universe@wsu.edu for a chance to be featured on my website.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

* Dear readers, what kind of science are you up to this week? Tweet @AskDrUniverse or tell me in an e-mail for a chance to win a Dr. Universe shirt.

Dear Dr. Universe, How does a chameleon change colors? -Jasmine B. 12, Nepean, Canada & Marie F., 11, Ghana

Dear Jasmine and Marie,

There’s something about a chameleon’s darting eyes, long tongue, curled tail, and ability to climb that makes it a fascinating animal to watch. Especially when it’s changing colors.

And the latest research on your question suggests that how a chameleon changes has more to do with light than scientists once thought.

That’s what I learned from my friend Paul Verrell, a biologist at Washington State University who studies animal behavior and works with reptiles. He said not all chameleons change colors. They also don’t necessarily use their colors to hide from predators. Since many are green, they often naturally blend in with plants in their environment. Instead, changing colors can help chameleons maintain their temperature or communicate that they’re interested in a mate.

“The big question is, how can chameleons change their colors so hugely, sometimes in very short periods of time?” Verrell said. “Well, let’s think of a different animal that can change its color. Octopuses are very famous for being able to change their color. They can change their color according to their moods.”

If we zoom into the cells that make up octopus skin we find tiny particles, called pigments, that give them their natural color. Depending on whether those pigments are packed closely together or farther apart, the color of the octopus changes.

For many years, people thought chameleon skin was very similar to that of octopuses. But now we know it’s not that simple.

Chameleon skin has quite a few layers. Underneath its scales are layers of cells with different pigments. The next layers are made up of crystals that create a crisscross pattern, or lattice.

The Swiss scientists who discovered these structures actually described them as selective mirrors, Verrell said. When light shines through a chameleon’s scales, it goes through the different layers and hits the lattices. The lattices reflect the light back out.
And they reflect the light out in different colors, depending on how closely the crystals are packed together in the lattice.

If the crisscross pattern is tight, we’ll usually see blue. But as light travels through the chameleon’s skin it may hit those tiny mirrors and bounce through some yellow pigments in the layer above. As it does this, we see green.

It’s almost like mixing blue and yellow paint to get green. But instead of paint, chameleons use light and their skin layers.

If the crisscross pattern of particles is looser, we’ll usually see more red. If the red passes through the yellow layer above, we’ll see more orange colors.

Another big question that remains is how exactly chameleons change these structures in their cells.

“I think the answer is we aren’t really sure,” Verrell adds. “The color changes are pretty rapid. I would hypothesize that it has something to do with its control by nerves, but we haven’t really worked out the details.”

As is often the case, the answer to your question leaves us with, well, even more questions.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

Dr. Universe: How do leaves make themselves? –Francesco R.

Dear Francesco,

Last fall, my friend Lee Kalcsits and I went exploring in the apple orchards of Wenatchee. The apples were ripe and the leaves were changing from green to gold. We plucked a few leaves and took them back to his lab.

“You know, if you take a stem, pull away all the mature leaves, and slice it from the top down, you can look at it under the microscope,” said Kalcsits, a scientist at Washington State University in Wenatchee who studies all kinds of trees.

He slid a tiny piece of the stem under his microscope and took a closer look.
“What it looks like is these tiny, moon-shaped leaves,” he said. “They get smaller and smaller until you get this dome-shaped structure and that’s the meristem.”

The meristem is the part of a plant where leaves begin to form, he explained.
It contains a bunch of building blocks, or cells. In a way, these cells are a lot like the ones animals have. Some of our cells will form into parts like our liver and muscles. Others will form into nerves and blood.

The meristem is a growing point for other plant parts like buds and flowers, as well as leaves, Kalcsits said.

While the meristem tells leaves to grow, sometimes trees get a signal to stop growing, too.
As the days get shorter and colder, some trees’ cells will start to act like scissors. They start “snipping” the leaves. The leaves fall and the tree gets ready to hibernate to survive the cold winters.

The meristem will also send a signal to the tree to form a small bumpy bud. A layer of scales will form around the bud to help protect it from the cold.

“Within that bud will be all the leaves and flowers ready for the next year,” Kalcsits explained.
In spring, as the weather warms up, new life emerges. Tiny green leaves start to sprout from the buds.

While the answer to your question can most often be traced back to the meristem, some leaves form in more unusual ways.
Some plants can use their leaves to clone themselves. If just one leaf drops, a whole new plant will grow from it.

In another example, leaves of pea plants can form into tendrils: curly leaves that start climbing and grabbing onto things. Other plants will grow thorns and stickers in place of their leaves to protect them from animals. Some leaves will even grow their own leaves. These are called leaflets.

Leaves are important because they help plants turn sunlight into their own food. The process helps the plants survive, which is good for other living things, too.

For one, plants give us food, like the apples I picked after I left Kalcsits’ lab. Of course, leaves also help give us the air we need to breathe. Without them, life on Earth wouldn’t exist as we know it.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.

  Is there any way to tell what color of eggs a chicken will lay? -Isabella, 8, Pullman, WA

Dear Isabella,

If you want to find out what color eggs a chicken will lay, you might just want to take a look at its earlobes. You read that right. Chickens have earlobes.

At first, I wasn’t even sure where I might find a chicken’s ears, let alone the lobes. And as a cat, working with birds can sometimes be a bit, well, awkward.

Fortunately, my friend Rocio Crespo offered to help out. She’s a Washington State University veterinarian who investigates diseases in birds, including chickens.

Crespo pointed out that a chicken’s ears are located on each side of its head, just below the eyes. Their ears don’t stick out like ours do, she explained.

“The ear is inside the head,” Crespo said. “It’s hidden behind some feathers.”

And the earlobe is just below the ear, marked by a slight thickening of the skin. It is bare of feathers. The earlobes can give us clues about the egg colors. Crespo said that if a chicken’s earlobes are white, the eggs it lays tend to be white.

After a bit of research, I discovered that all bird eggs start out white. But sometimes, while the egg is developing, certain pigments give the shell color.

Birds are actually the only animals that lay colored eggs. As you may know, some chickens lay brown eggs. If a chicken lays brown eggs, it is likely that she has red earlobes.

As usual, there are some exceptions to the rule. Some chickens with red earlobes may also lay greenish eggs or blue eggs.

While there seems to be an earlobe–egg correlation, scientists aren’t entirely sure why. But it might be because the genes that hold the instructions for earlobe and eggshell color are close together, Crespo adds.

Crespo said the key to really understanding egg color goes back to a bird’s genetics.

Scientists can learn more about birds as they look at the genotype, or the genetic makeup, of the organism. It’s like exploring a set of instructions for how an organism will develop.

They can also look at the phenotype, or the physical traits we can observe. For example, feather and eggshell color.

“It’s all part of the genetics,” Crespo said. “That’s part of why your skin is white or brown, or why your hair is red or blonde or black. It’s the same thing with the chickens. The egg color is part of their breed.”

Depending on the breed, a hen will lay about 500 eggs in her lifetime. And whether an egg is brown or white, it’s still the same on the inside. They taste the same and are equally nutritious.

A few readers have also been wondering which came first—the chicken or the egg. It’s a good question. But we’ll save that one for another time.

In the meantime, try making a bouncy egg and explore other experiments at pinterest.com/AskDrUniverse. Send a picture of your project to Dr.Universe@wsu.edu for a chance to be featured on askDrUniverse.wsu.edu.

Sincerely,
Dr. Universe

How is chocolate made? –Lydia, 6, Bedfordshire, England

Dear Lydia,

A few thousand years ago, humans discovered that beans inside the bright green pods of cacao trees could be made into a real treat.

In South America, people harvested the beans to make a warm, chocolaty drink. Ever since, we’ve found ways to make all kinds of chocolate from cacao beans.

“Chocolate is both a science and an art,” said my friend Jessica Murray. She’s an expert on chocolate and a graduate student in food science and business at Washington State University.

She explained that cacao beans can be separated into a couple different parts. We can extract the fat, or cocoa butter, from the beans. The rest of the bean can be ground up into solids. When we mix these two parts back together, we can make dark, white, or milk chocolate.

In Murray’s kitchen here at the university, she takes 10-pound bricks of chocolate and melts them to 115 degrees Fahrenheit. It turns into a nice, chocolaty liquid.

“Making chocolate is a lot like the experiment where you grow sugar crystals in a jar,” she said.

If you’ve ever tried this experiment, you know that sugar crystals grow on a string inside a jar full of sugar water. In a couple weeks, as the crystals multiply, a giant crystal is left in the jar.

Cocoa butter actually contains crystals, too. It has thirteen different kinds.

“You can’t see the crystals unless you look under a microscope, but that’s what makes the chocolate set correctly and all shiny,” Murray said.

If you’ve ever let a chocolate bar melt on a hot summer day, then later noticed it had a bunch of white spots, you’ve seen some of these crystals in action.

As a chocolatier and a scientist, Murray is after one particular crystal to make the chocolate look and taste the best: the beta crystal.

“But crystals have to have something to grow off of. They don’t just miraculously happen, they have to form,” she said.

When making chocolate, Murray will add more solid chocolate to the liquid chocolate, to help the beta crystals form. The solid chocolate is added into the batch when the temperature of the melted chocolate reaches precisely 105 degrees.

Once the conditions are right, a beta crystal will form. Then, the chocolate is ready to be poured into molds.

“You fill the mold, let it cool, then tip (the mold) upside down, you kind of spin it around and it flings chocolate everywhere and makes a giant mess. But it’s really fun,” she said.

Once the chocolate cools and becomes a solid again, she can add fillings or creams. This year she’s starting her own line of chocolate. She’s calling it WSU Crimson Confections.

As much as I’d like to try Murray’s new chocolates, we cats can’t taste sweets. I’ll have to leave the taste-testing experiments up to those of you with a sweet tooth.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University. Visit askDrUniverse.wsu.edu to watch the making of chocolate video.

Why is yawning contagious? –Grant, 10, Pullman, WA

Dear Grant,

When I got your question, I met up with my friend Hans Van Dongen, a scientist at Washington State University in Spokane. He works in a research lab where they study sleep. As a cat who appreciates naps, it’s one of my favorite places to visit.

He explained that while yawning is common for lots of animals, we still don’t know why it happens. We do know that once you start a yawn, there’s no stopping it. And as you’ve observed, yawns can be quite contagious.

If someone yawns, people who see the yawn may soon start yawning, too. Some scientists think that the contagiousness of yawns might actually be a way for humans to communicate.

Van Dongen said a lot of people used to think that yawning was a sign of boredom. But after a while, they weren’t so sure about that theory. If you are watching a movie or listening to a long lecture, you might start to yawn, but it might not mean you’re bored.

When you stretch your jaw, breathe in, and let out a yawn, it might be that you’ve slowed down long enough to realize an important fact: You might need to be getting some more sleep.

If a friend catches the yawn, they just might be saying, I could probably use some more sleep, too.

“And this is not an insignificant issue,” Van Dongen said. “Because we mask our sleepiness by being busy all day.”

People generally have a lot of work to get done, so they have to keep busy. Working together in a group was especially important for human survival a long time ago.

While people don’t rely on one another for survival as much these days, yawning still may be a way to communicate among the whole group that everyone needs sleep to be successful.
“Really the only theory that gets circulated much at the moment is that it is a social signal to say, ‘You know what—we should maybe all time out and sleep a little bit more’,” Van Dongen said. “Maybe take a nap or make plans to go to bed earlier tonight.”

After all, the survival of the group often depends on the survival of an individual person. So, it’s important to make sure that the individual people aren’t tired, cranky, or distracted.

“And if yawning is alerting us to that and we are ignoring it because we don’t think much of it, maybe we are losing a lot of money and lives because of drowsiness that could have been avoided,” Van Dongen said.

Catching a yawn could help humans let each other know they should be catching some more Z’s. But maybe there’s more to the story, too. Perhaps you could be a scientist and help us get to the bottom of it.

Sincerely,
Dr. Universe

Got a science question? E-mail Dr. Wendy Sue Universe at Dr.Universe@wsu.edu. Ask Dr. Universe is a science-education project from Washington State University.