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Why does stuff decay?

Dr. Universe: I have a ginormous question for you. How come non-biodegradable take like a million, billion, zillion years to decay? -Madeline C., age 8

Dear Madeline,

You’re right. It can take a really long time for some things to decay.

If we buried an apple peel in the backyard it might only take a few weeks to break down into the soil. But if we buried a plastic water bottle, it would probably still be there hundreds of years from now.

There are a lot of living creatures in nature that help break down things. In fact, our trash cans are almost like an all-you-can-eat-buffet for tiny creatures called microbes. Well, an almost all-you-can-eat-buffet. There are some things that they can’t really feast on. It all depends on what’s in our trash bins.

For billions of years, microbes have been munching on plants and animals. They’ve also had some help from fellow decomposers, like worms, flies, and fungi.

The environment where they work can also speed up or slow down the process. The conditions of dirt, air, water, temperature, and sunlight can change the speed of decomposition.

These decomposers are pretty great at breaking down a lot of things we find in nature. But they aren’t as good at breaking down some other materials, such as plastic.

To find out why, I visited my friend Shuresh Ghimire, a scientist who studies biodegradables at Washington State University. He is also really curious about finding ways to decrease the amount of plastic waste in our world, particularly on farms.

Plastics were introduced in the 1930s, he explained. Now, that may seem like a long time ago to us. But for microbes that have been around for billions of years, that’s still a pretty new material.

Both an apple peel and a plastic bottle are made up of different kinds of atoms. Those atoms are bonded and held together in different ways. In an apple, the bonds between atoms are pretty weak. Microbes don’t have to use a lot of energy to break them into smaller parts.

But the plastic bottle has really strong bonds—especially where a carbon atom bonds with another carbon atom. It makes the material sturdy, but it also makes it pretty indestructible. Most microbes don’t recognize these bonds as something they can break down, at least not yet.

“There is a possibility that evolution of microbes over many years in the future may enable more of them to recognize bonds in plastics,” Ghimire said.

In fact, a group of scientists in Japan recently discovered a microbe that looks to be pretty good at eating plastic. They might be able to help us manage some of the plastic waste, but we can help, too.

A water bottle might last hundreds of years buried underground or in a land fill, but it could have a new purpose in our own lifetime if we remember to reuse or recycle it.

Sincerely,
Dr. Universe

Why are whales so large?

Dear Dr. Universe, Why are whales so large? -Hannah, Grand Island, NE

Dear Hannah,

Of all the whales that live in the sea, the largest are blue whales. In fact, blue whales are the biggest known animals to have ever lived on our planet. Yep—even bigger than dinosaurs. » More …

Why do animals hibernate?

Dear Dr. Universe: Why do animals hibernate? -Jarrett T., 10, Edinburgh, IN

Dear Jarrett,

Animals can get through winter in all kinds of ways. Us cats like to curl up on a cozy couch. Some penguins huddle in groups to create heat. A lot of birds fly south to warmer weather. Perhaps you put on mittens and a coat. » More …

How long can trees live?

Dear Dr. Universe: How long can trees live? -Jessy, 8, Seattle, WA

What kinds of trees are in your backyard? Do they have pinecones? Colorful leaves? Pods with seeds? Tell us more or send a picture to Dr.Universe@wsu.edu.

Dear Jessy,

As I was hiking through the bristlecone pine forests of the Sierra Nevada recently, I stumbled upon a tree barely six inches tall.

It was growing—slowly, but surely. I was surprised to find this tiny pine tree was already about 40 years old.

Some trees will stop growing once they reach that age. But others live much longer. In fact bristlecone pine trees aren’t just the oldest trees, they are some of the oldest living things on our planet. They can live for about 5,000 years.

“These trees were growing when the Egyptians were building the pyramids,” said my friend Kevin Zobrist, a forester at Washington State University.

Zobrist knows a lot about different trees and told me a bit about bristlecone pine trees.

By the time the pines are about 5,000 years old, they will stand 60 feet tall with a trunk that is nearly five feet around. If we were to cut into the trunk, we could look at its growth rings. Each ring would signify a year of its life. We would have a lot of counting to do.

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Click to zoom in.

On my hike, I noticed some of the trees’ young pinecones were purplish-pink. Eventually they would turn brown and fall to the ground. I spotted a few old cones by the tree. They had that fresh pine scent.

I looked up at the branches that twisted and stretched like arms up to the sky. I wondered how on earth these trees were able to live such long lives.

Zobrist explained that bristlecone pine trees are tough and have adapted to their environment. They are equipped to deal with drought, extreme climates, and insects that might cause serious damage if they attack.

For example, the tree can actually shut down or go dormant for a while, if conditions are too harsh. This helps the tree survive for thousands of years.

“They teach us that nature is resilient,” Zobrist said. “They teach us that nature can carry on.”

Of course, not all trees live quite as long as these pines. But many live longer than humans and us cats.

The redwood trees of California are about six times taller than the bristlecone pines. Some of them have been around for nearly 2,000 years.

Even when a tree dies, it finds a new life. Creatures and plants on the forest floor are counting on the trees to get old, die, and fall. They can use the fallen trees as their home or for food.

It’s been said that trees are our planet’s lungs. They help make the oxygen we breathe and keep life thriving on our planet. I took a deep breath of the mountain air and said a quick thank you to the trees before heading down the trail, on to the next adventure.

Sincerely,

Dr. Universe

How do cats land on their feet?

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. » More …

How do spiders make silk?

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. » More …