Dear Dr. Universe: How does a light bulb work? When one bulb in a string of lights goes out, why do they all go out? – Molly, 8

Dear Molly,

Just the other day I was taking down a string of lights from my lab, when I discovered the bulbs were burnt out. I visited my friend Aaron Crandall, an engineer at Washington State University, to see if I might get them working again.

Crandall explained when you plug in a string of lights to a power source, like an outlet, an electrical charge flows into the wires. A lightbulb works when an electrical current runs through thin metal wires in the bulb and electrical energy gets converted to heat and light. We can get this current of electricity to follow different paths, depending on how we wire up the lights.

When the electricity reaches the first bulb in a string of lights, it flows up a tiny vertical wire inside the bulb. Here, it crosses a tinier horizontal wire, which acts kind of like a bridge, for the electrical current. The current follows another tiny vertical wire down and out the bulb. The current moves on, powering up the other lights, until it gets back to the power source. It’s all part of a looped pathway.

My string of lights is on one long path, or circuit— if one of the lightbulbs goes out, they all go out. Usually this happens when the tiny wire bridge that connects those two vertical wires inside the bulb melts or breaks.

Crandall said in some sets of lights you can gently shake the bulb to try and get the tiny horizontal wire to reattach to the vertical ones. I attempted this with my broken lights, but didn’t have much luck. I decided to pick up a new set of lights. This newer set has individual loops, or circuits, for each light. It also requires more wire to work.

You might think of this type of circuit like the monkey bars on a playground. Imagine the view from the top. There are two parallel bars that connect to rungs (the part you swing from). Let’s say you and a few friends are lightbulbs. You each hang from your own rung.

A circuit called a series circuit would be kind of like if you and your friends (the lightbulbs) were all holding hands and the current was flowing down the line. If one friend left, it would break the connection.

But on the monkey bars you aren’t holding hands. You have your own connection (rung) to the lines the electricity is flowing along (the parallel bars). In this kind of design, each light or a series of lights has its own loop, or circuit. If one route along the electrical pathway is not working or blocked, the rest of the bulbs can still light up.

I’ll put up my new lights next year, but I think I’ll break apart my old set of lights to do some experiments with circuits. With some help from an adult, you can check out how to make your very own circuit with old holiday lights. Tell me how it goes sometime at Dr.Universe@wsu.edu.

Sincerely,

Dr. Universe

Dr. Universe: How do planes fly? -Tahira, 12, India

Dear Tahira,

Planes are very heavy, yet they stay up in the air kind of like a bird in the sky. They can get us across the world in less than a day. Humans went from learning how to fly a plane to putting a man on the moon in a little over 60 years.

But the answer to your question goes even further back. It goes all the way back to the 1700s and actually started not with air, but with water.

That’s what I found out from my friend Michael Allen, a physics and astronomy professor at Washington State University. He thought you asked a great question and was happy to tell me all about how planes can fly.

Around 300 years ago, a scientist from Switzerland named Daniel Bernoulli was experimenting with water pipes, like the ones under your sink at home. When water (or anything) moves through a small space, like the inside of a pipe, it puts pressure on that container (the pipe.)

The more air you push into a smaller space, the greater the pressure. Allen told me that Bernoulli found out that the faster the water moved through the pipe, the less pressure the water put on the pipe.

This idea has come to be known as Bernoulli’s Principle. This principle doesn’t only apply only to water, it also applies to air that passes over the wings on an airplane.

Allen told me that wings on an airplane are flat on the bottom and curved on the top. Allen said that as the wing moves through the air, some air goes over the top of the wing while some goes under the bottom of the wing.

However, the air that goes over the top of the wing has to go over a longer distance than the air under the wing because of the curve. Allen also said the air has to get past the wing at the same time, meaning the air above must travel faster, just like the water moving quickly in the pipe.

Since this air above the wings travel faster, there is less pressure above the wing than below the wing, which pushed the wings and the plan up into the air, causing the plane to fly.

Thanks for your question. It was a great one and I’m happy that you have such a big interest in airplanes. Have you ever thought about becoming a scientist or engineer that works on planes one day? Maybe you could make the next spacecraft that takes a person to the moon or Mars.

Sincerely,
Ian Smay and Dr. Universe

Ianb Smay contributed this article. He is a student in the Edward R. Murrow College of Communication at Washington State University.

Hello Dr. Universe, may I ask how fish breathe? – Nghi, 11, Vietnam

Hello Nghi,

Cats, humans, and fish all breath for the same reason. We need oxygen. Oxygen is one of the things our bodies use to make energy.

Just like the hungry feeling you get when you haven’t eaten, your body uses oxygen to keep everything running. Unlike the breaks you take between meals, the breaks you take between breathes are much shorter. Most people take about 12 breaths per minute.

While it may seem like we breath only oxygen, there are lots of other gasses in the air. When we breath in, our lungs fill up with all this gas. The lungs take the oxygen out of the air and breath out all the rest of the air our body doesn’t use.

In addition, we breath out carbon dioxide. It’s a gas our body produces when it makes energy. Just like how your body sweats when you play sports, your body makes carbon dioxide when it breathes.

Fish also use oxygen to keep their bodies running, but the oxygen that they use is already in the water.

Their bodies are built differently than ours. Humans and cats have lungs, while fish have gills.

That’s what I found out when I went to visit my friend Michael Berger. He’s a biologist at Washington State University.

You can see a fish’s gills when you look at their faces. They are lines on the sides of a fish’s face. The gills are also inside the fishes’ body, but those can’t be seen from the outside– just like our own lungs.

Berger explained that you can see a fish breathe in water because their face gets bigger when it’s full of water. Just like when you take a big bite of food.

First, the water goes into the fishes’ mouth and through the gills. As the water leaves the gills it returns to the ocean. Additionally, the carbon dioxide the fish creates is also removed as the water leaves the gills.

Berger shared a fun fact with me during our visit: Fish and other animals with gills are able to get oxygen to breathe because their blood flows through the gills in the opposite direction of water. If their blood flowed through the gills in the same direction as the water, the fish would not be able to get as much oxygen from it.

The gills are a like a filter and they collect all the oxygen the fish need to breath. After the gills pick up the oxygen, it is sent throughout their blood and fuels their bodies.

That’s why it’s important to leave fish in their home. Without water, they are unable to get the oxygen needed to stay happy and heathy.

If humans would like to breath underwater like fish, they can use a snorkel to experience life like a fish. Most snorkels kits include a mask and a mouth piece. The mouth piece is attached to a tube that reaches above water. That way, humans can keep breathing air while their mouth and nose are under water.

Sincerely,
Amanda Tomchick (and Dr. Universe)

Amanda Tomchick contributed this article. She is a student in the Edward R. Murrow College of Communication at Washington State University.

Dr. Universe: Why do birds have feathers? –Karthikeya, 7

Dear Karthikeya,

Bird feathers are interesting. There are so many types, shapes, and colors. My friend Daniela Monk is a Washington State University professor who studies avian ecology, or the study of birds.

She told me about why the birds we know today have feathers and how they got them. Researchers believe that birds evolved from dinosaurs a very long time ago.

“One lineage of dinosaurs gave rise to birds,” Monk said.

Researchers around the world are finding dinosaur fossils that contain feathers. A fossil is the remains of a very old animal or plant that is preserved in a rock. From these fossils they are learning that some dinosaurs used to have feathers, but for other reasons than flying.

Monk said that early feathers likely provided those dinosaurs with insulation and enabled them to stay warm at night, just like in mammals where fur likely was selected for to keep them warm. Some of these feathered dinosaurs were small and needed to protect themselves from other animals that would harm them.

One possibility is that early feathers may have provided them with the ability of escaping. At first, these dinosaurs likely couldn’t fly very well and may have flapped their wings to better run up tree trunks or to glide from place to place.

Over a long period of time, some feathered dinosaurs became accomplished flyers. They became lightweight and airborne, like the birds we know of now.

Monk said that feathers even in dinosaurs may have had a function in addition to flight. They may have been used for communication. Birds have so many different colors and patterns of feathers, some are for protection while others are for attracting mates.

Male birds are typically very colorful while females are tan and brown so they can blend into their habitat and stay safe. Have you seen a peacock? Male peacocks have very colorful feathers, while the females have brown feathers.

If you find birds fascinating like I do, then maybe you can become a bird watcher. It’s simple. All you need do is watch the birds that live around your house and write down what you see and observe. How many different birds can you spot in your neighborhood?

Sincerely,
Bailey Campbell and Dr. Universe

Did you know not all birds fly? Penguins and Ostriches are flightless birds.

Bailey Campbell contributed this article. She is a student in the Edward R. Murrow College of Communication at Washington State University.