Dear Haygarth,

I love glow-in-the-dark stickers. I leave them next to a sunny window for a little while. Then turn off the lights and watch them glow.

I asked my friend Hergen Eilers how those stickers work. He’s a physicist at Washington State University.

He told me that glow-in-the-dark things use a type of phosphorescence. That means they absorb energy—like light—and then glow. A material that can do that is called a phosphor.

Glowing in the dark works because of electrons.

Everything in the universe is made of atoms. That includes you, me, whatever you’re reading this note on—and glow-in-the-dark stickers.

All those … » More …

Dear Remmi,

Mars is about 140 million miles from our cozy planet. A human mission to that cold, rocky neighbor would mean being away from Earth for about 3 years. But the things those explorers would see and learn would be mind-blowing.

I asked my friend Katie Cooper about that. She’s a scientist at Washington State University. She studies how geology and physics work on Earth and other places in space.

She told me the weirdest thing on Mars is a ginormous volcano.

“Olympus Mons is the largest volcano in the solar system,” Cooper said. “It dwarfs Earth’s volcanoes! Its massive size helps … » More …

Dear Dean,

There’s a pencil lying on my desk right now. It’s not much to look at, but what if I could zoom way in and see the protons and other itty-bitty stuff inside it?

My friend Ryan Corbin told me it would be like looking at a bubbling soup of fundamental particles. He’s a quantum physicist at Washington State University.

He told me that protons—along with neutrons—form the nucleus in the middle of an atom.

“Atoms make up all the stuff that we see,” Corbin said. “An atom has neutrons and protons in its nucleus. Protons have a positive electric charge. Neutrons … » More …

Dear Zara,

I love visiting the vet. But, like many cats, sometimes I need medicine to keep me calm.

I talked about that with my friend Lais Malavasi. She’s a veterinarian at Washington State University.

She told me about two kinds of calming medicine. Vets and human doctors use them to reduce pain and fear.

Sedatives make patients feel relaxed and sleepy. But they’re mostly aware of what’s going on. When the medicine wears off, they’ll probably have fuzzy memories.

Anesthesia makes patients unconscious. They can’t feel pain or move. They aren’t aware of what’s going on. When they wake up, they won’t … » More …

Dear Dru,

When it comes to intestines, it sure seems like two are better than one.

I asked my friend Franck Carbonero why that is. He’s a microbiologist at Washington State University. He studies the bacteria that live inside the human gut.

He told me that the small intestine and the large intestine do different jobs.

Let’s say you sink your teeth into some pizza. You chew it up and swallow it. All those chewed up bits land in your stomach. They mix with digestive juices and start to break down. The broken-down food and digestive juices together are called chyme. After … » More …

Dear Lucy, 

Cats like me don’t have wisdom teeth. So, imagine my surprise to learn some of my human buddies get extra chompers. 

I asked my friend David Carsten about it. He studied biochemistry at Washington State University. Now he’s a dentist who teaches about dental sedation and anesthesia at Oregon Health & Science University. 

Dr. Carsten told me that humans can get three sets of permanent molars. Molars are the big grinding teeth in the back of your mouth. The third set—also called wisdom teeth—usually come in when you’re between 17 and 21 years old. If you get them at all. 

Wisdom … » More …

Dear Devyn,

I love insects, but—between you and me—I’m a little scared of spiders. I’ve been nervous around them ever since I was a kitten.

I talked about our fears with my friend Paul Strand. He’s a psychologist at Washington State University.

He told me that anxiety about insects or spiders is common. Some people even have phobias of them. That’s an intense fear that causes distress.

Many common fears involve things that were probably dangerous to our ancestors—like snakes, the dark, heights and social rejection.

Strand told me that being afraid of insects is similar.

“It’s almost like a double whammy,” he said. … » More …

Dear Hailey,

Under my lab coat, I have a splendid fur coat. That can be a problem when I work with someone who’s allergic to cats.

I asked my friend Ed Johnson about it. He teaches classes about the human body at Washington State University.

He told me that allergies happen when your immune system overreacts to a normal thing it perceives as a threat to your body. That thing can be pollen, dust, food, medicine, insect venom or something else. It can be bits of fur and shed skin called cat dander.

“The immune system evolved to protect the body,” Johnson said. … » More …

Dear William,

There are lots of unpleasant things about being sick. Leaking slimy green snot is near the top of my yuck list.

I talked about it with my friend Linda Eddy. She’s a nurse for kids. She runs the nursing program on the Vancouver campus of Washington State University.

She told me that snot is normally clear. It turns yellow or green when our bodies fight germs that can make us sick.

Snot is also called mucus. It’s a thin, slippery liquid that covers many of the surfaces inside our bodies. You can find mucus in your nose, mouth and eyes. It … » More …

Dear Sarah,

Tuna, salmon, mackerel. Cats like me are famously big fans of fish. But I’ve never looked at my afternoon sushi and wondered if it’s related to my human friends.

So, I asked one of those friends named Thomas Siek. He’s a biological anthropologist at Washington State University. He studies how humans evolved.

He told me that fish and humans are distant relatives. All vertebrates—animals with backbones—are related.

“Humans and fish aren’t close evolutionary cousins,” Siek said. “We’re part of the same phylum called Chordata. We share a common ancestor. Those in Chordata have backbones. So, this will also include birds, dogs, … » More …