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Part 3: Where does our garbage go?

Dear Dr. Universe: What happens to the world’s garbage? -Presley, 8, Spokane, Wash.

How do you recycle an object into another object? -Brianna, 12, New York

Dear Presley and Brianna,

So far, we’ve investigated how recyclables like plastic, aluminum, and paper can end up in the trash. If our clothes get damaged, or we simply outgrow them, we might toss them in the trash, too. Or send them to a thrift shop. Either way, they often end up buried in a landfill. » More …

Part 2: Where does garbage go?

Dear Dr. Universe: What happens to the world’s garbage? -Presley, 8, Spokane, Wash.

How exactly do you recycle an object into another object? -Brianna, 12, New York

Dear Presley and Brianna,

While a lot of our trash goes in a landfill, we can also recycle all kinds of stuff on our planet. Depending on what the object is made of, we might grind it up, mix it up or melt it down before we turn it into something new.

Let’s start with paper. When you recycle paper, it usually ends up at a recycling center where it gets washed with soapy water and mixed into a huge, thick slurry.

Sometimes we add a few other ingredients if we want a specific kind of product, like cardboard or printer paper. The slurry is poured out onto a big table and flattened with big rollers. After it dries, it can be cut into different sizes and shipped to stores. Recycling is a great way to help us make new paper without cutting down more trees.

Melting down materials 

WIllustrated, cartoon cat with labcoate can also recycle things like glass, plastic and aluminum. A lot of these materials are mixed together in a recycling bin, so the first step when they arrive at a recycling center is to wash and sort them. Engineers have built conveyer belts and equipment to help divide up the different items into groups.

Once they are divided up, they can be melted down, cooled and shaped into flat sheets or new objects. A glass bottle might become a jar, a plastic bottle might become part of recycled clothing and a soda can might become another soda can.

While different objects go through different recycling processes, most of the time we break them down before we build them up into something new. But some materials that we want to recycle don’t break down quite as easily.

Breaking it down with Dr. Zhang

While most of us put smaller items into the recycle bin, we also have lots of really huge stuff we need to recycle, too. Things like airplane wings and giant blades from windmills often end up in landfills. My friend Jinwen Zhang, a scientist at Washington State University, is helping research ways to recycle the lightweight materials and keep these big objects out of landfills.

This kind of lightweight material, carbon fiber plastic, they work with in the lab can’t melt down like a lot of other things we recycle. Zhang and his team figured out a different way to break them down using just the right environmentally-friendly chemical mix.

Exactly what kinds of objects those wings and blades will become is a question that we are still looking to answer. It will inspire more research and help us understand how to recycle things that couldn’t really be recycled before we learned to break them down.

These are great questions you ask, Brianna and Presley. Thank you for being curious. We can help make the planet a safer and healthier place to live when we recycle.

Dr. Universe

Part 1: Where does garbage go?

Dear Dr. Universe: What happens to the world’s garbage? -Presley, 8, Spokane, Wash.

Dear Presley,

If you’re anything like me, maybe one of your weekly chores is helping take out the trash or making sure all your tuna cans get into the right recycle bin. The truth is, I wasn’t entirely sure where the garbage goes either, so I decided to ask my friend Karl Englund. » More …

Why do bees have pointy behinds?

Dear Dr. Universe: My daughter is asking, why do bees have pointy behinds?

-Asma, Pakistan

Dear Asma and Friends:

Lots of bees have pointy behinds, but not all of them. The ones that do have a pointy behind, or a stinger, can use it to help defend their homes, food, and fellow bees. That’s what I found out from my friend Megan Asche, a graduate student at Washington State University who studies honey bees and takes super close-up photos of insects. » More …

Where did the first nerves come from?

Dear Dr. Universe: Where did the first nerves come from?

– Max, 4, Pullman, Wash.

Dear Max,

Clap your hands. Stomp your feet. Blink your eyes. Every time you move, the brain and body send messages to each other. Under your skin, your nerves stretch out like a network of wires across the body. They help carry these messages from one part of the body to another. » More …

Why are animals symmetrical?

Dear Dr. Universe: Why are animals symmetrical?

– Theo, 10, Rupert, British Columbia, Canada

Dear Theo,

That’s an excellent observation. If we drew an imaginary line straight down the middle of the human body, it would look pretty similar on each side. » More …

Do you have any experiments you can recommend?

Dr. Universe: Do you have any experiments you can recommend? Thanks! -Etta, 7, Milwaukee

Dear Etta and Friends:

You can try all kinds of fun experiments at home. It really all depends on what you are curious about. Lately, I’ve seen some really great sunsets and started wondering what gives them their colors.

I decided to ask my friend Tom Johnson, who leads fun physics demonstrations for kids visiting Washington State University. I asked him if he had any simple ideas for an experiment I could try out in my lab, or even the kitchen. One idea he had was to create a sunset in a cup.

Maybe you can try it, too. You’ll need a flashlight, a transparent cup or two, water, and some milk. We cats have a reputation for liking milk. But it really isn’t so great for our digestion. So instead, I like to use it for science.

Once you’ve collected all your supplies, you’ll want to fill your glass about 2/3 of the way with water. Then, you’ll want to add milk until the liquid gets pretty cloudy. Be sure and stir it up well.

Turn on your flashlight and turn down any other lights in the room. Now you can shine the flashlight down into the water and look through the side of the glass. What color do you see?

This time, shine the flashlight through the side of the glass while looking at it from the opposite side. Any changes? Then hold your glass up off the table. Shine the flashlight up through the bottom of the glass and look down into the liquid. What colors can you see now? Perhaps the colors are looking more like those you’d see during a sunset.

Milk in the water scatters the light from the flashlight. It’s similar to the way different molecules and dust in our atmosphere scatter light from the sun.

Light travels from one end of the glass to the other and then up to your eyes. The further the light has to travel through the water, the more blue light gets scattered. That leaves more red light for your eyes to pick up.

Now that we’ve started to get an idea of how light scatters, runs into particles, and travels long distances, you can really get to experimenting.

What happens when you use less or more milk? Will you see any changes if you use a different kind of flashlight, like an LED? What kind of milk gives off more orange or reddish colors? Two percent? Whole milk?

Does the shape of the glass change anything? Why do you think that might be? Make a prediction and give it a try sometime. I’d love to hear more about your experiments and how your own sunset in a cup turns out. E-mail:

Dr. Universe


  • Ask Dr. Universe connects K-8 students with researchers at Washington State University through Q&A. Students can submit science questions on the ASK page.
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How do we get our personality?

Dr. Universe: How do we get our personality? – Jamie, 11

Dear Jamie,

Everyone is different. Maybe you are adventurous, shy, outgoing, funny, or kind. Before you were even born, your unique personality was beginning to take shape. » More …