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Ask Dr. Universe earth
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Why does the Earth have lava in the middle? – Nora, 6, Florida

Dear Nora,

I live near a few volcanoes. One of them—Mount St. Helens—is bubbling with molten material that will probably gush out as lava someday.

I asked my friend Johannes Hämmerli about lava. He’s an earth scientist at Washington State University.

He told me Earth is mostly solid.

“The very center of Earth is a solid metal ball,” Hämmerli said. “Outside that ball, there’s a thick shell we think is liquid. And the rest of Earth—if you go through the mantle and crust—is pretty much solid.”

Earth formed when a cloud of dust in space collapsed. The elements inside the cloud squished … » More …

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How was the Earth made? — Penny, 8, Washington state

Dear Penny,

Blue oceans, green forests, a cozy blanket of oxygen. Our planet is a super comfy home. It’s hard to imagine there was ever a time it didn’t exist.

I asked my friend Julie Ménard how Earth formed. She’s a planetary scientist at Washington State University.

She told me it started with the Big Bang. That was nearly 14 billion years ago.

“The Big Bang is not an explosion,” Ménard said. “It’s an expansion. Everything in our universe today was in a tiny spot—smaller than the eye can see. Eventually, the pressure and density got so high that it started to expand.”

… » More …

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Why can we sometimes see the moon during the day? – Eli, 7, Texas

Dear Eli,

I love to go for a walk with my dog roommate. Sometimes we see the moon in the sky—even though it’s daytime.

I asked my friend Michael Allen why that happens. He’s an astronomer at Washington State University.

He told me that we have to ask “what is a day” to answer your question.

“The sun lights up the earth,” Allen said. “Since the earth is a round ball, only half of the ball can ever be lit up at any one time.”

The side of the earth that the sun shines on experiences day. The side that faces away from … » More …

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What would happen if you put a baseball-sized piece of neutron star on the Earth? Would it fall to the core of the Earth and become part of the core or pass through the Earth? – MacKenzie, 12, Louisiana

Dear MacKenzie,

A neutron star is what’s left after a massive star runs out of fuel and explodes as a supernova.

I asked my friend Matthew Duez about it. He’s an astrophysicist at Washington State University.

He told me that a neutron star is the densest known object in the universe. Its mass is like the sun’s mass. But a neutron star is the size of a city.

When something is dense, it has lots of stuff—or mass—crammed into a small space.

Imagine if we took all the humans on the planet and squished them together. We mash and squash them until they fit … » More …

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Why do we have to go to sleep at night, but the other side of the world is having morning? – Braelyn, 12, Ohio

Dear Braelyn,

If I drew a straight line through the Earth to the opposite side of the planet from me, I’d hit a place called Port-aux-Français. That’s an island near Antarctica. Mostly scientists live there.

Right now, it’s 12 PM, or noon, on Friday for me. But those scientists are probably snoozing in their beds. For them, it’s after 12 AM, or midnight, on Saturday. They’re already living in my tomorrow. Weird!

I talked about why that is with my friend David Luftig. He’s a science librarian at Washington State University. Science librarians are experts in two things: science and helping people find information for research and learning.

He told me it’s all because of Earth’s rotation. As the Earth rotates, or spins, the sun shines on one part of the Earth at a time.

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How did life begin? Kelsey, 10, Texas

Dear Kelsey,

The universe is a big place. Thinking about how we fit into it is part of what makes humans (and cats like me) special.

I talked about your question with my friend Afshin Khan who studied astrobiology and environmental science at Washington State University. Astrobiologists explore how life began. They also look for signs of life outside Earth.

Khan told me your question is a huge mystery.

“We have very good ideas about what could have happened,” she said. “In different labs around the world, we’ve gotten very close to simulating some of those conditions. But simulations can only get so … » More …

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Dr. Universe: Why do we have seasons? -Bella, 9, North Carolina

Dear Bella,

It turns out seasons can be quite different depending on where you live. But no matter where you live, the reason for the seasons has to do with the way the Earth rotates.

To find out exactly why we have seasons, I talked to my friend Vivienne Baldassare, a physics and astronomy professor at Washington State University.

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