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Ask Dr. Universe Environmental Studies
University Communications Network > Ask Dr. Universe > Academic Subjects > Earth Sciences > Environmental Studies

How many atoms are in a leaf? – Lily, 8, Georgia

Dear Lily,

I love thinking about things I can’t see with just my eyes. Like the atoms that make up everything.

I asked my friend Fred Gittes how to figure out the number of atoms in a leaf. He’s a physicist at Washington State University.

He showed me a worksheet he gives his students. It included a question exactly like yours!

“It’s a question I assign college students for fun,” Gittes said.

So, you’re in great company when you ponder big questions like this.

We decided to use stoichiometry to find the answer. That’s a kind of math that scientists do to understand chemical reactions.

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Why do trees have bark? – Grant, 5, Texas; William, 7, Virginia; Kate, 9, Florida

Dear Grant, William and Kate,

When I was a kitten, I liked to scratch tree trunks. I loved sinking my claws into their bark. Now I mostly hug trees—but I still love the way bark feels under my paws.

I asked my friend Henry Adams why trees have that tough outer layer. He’s a tree scientist at Washington State University.

He told me that bark protects trees.

“Bark is like our skin,” Adams said. “It protects trees from all kinds of attackers that might want to get in—like viruses, bacteria, fungi, insects or even non-living things like fire.”

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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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What is octopus ink? – Henry, 6, Maryland

Dear Henry,

An octopus has three hearts and long arms with suction cups. It probably seems very different from you. But you have the main ingredients of octopus ink in your body, too!

I talked about octopus ink with my friend Gretchen Rollwagen-Bollens, associate professor in WSU’s School of the Environment. She told me that ink isn’t just an octopus thing. Most animals called cephalopods (sef-uh-luh-pods) make it. These include octopus, squid and cuttlefish.

Cephalopods including octopuses use color a lot. They have sacs of colored pigments all over their bodies. They use those sacs to change their body color. That helps them blend into their environment.

They also make and store a dark pigment in special ink sacs.

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