Molly Mermaid
Learns Physics Lisa Ball
O
nce upon a time, far away, under the sea lived a beautiful mermaid. Her name was Molly. She lived in a clear blue cove near the Island of Serenity. Molly was always curious about the island and would often swim near the beach and watch the children play, but she was careful not to ever let them see her. When she was a little mermaid her mother taught her the dangers of the sea. “Land people try to catch mermaids”, her mother told her. “Why Mama?” Molly wanted to know. “Because you are very special.” Her mama hugged her. The Island of Serenity was a paradise surrounded by beautiful blue water and white sand. Molly swam around the entire island and saw that only a few families lived on the island. Tall palm trees cast shadows on their tiny huts. Molly watched the children digging in the sand and making dolls from palm fronds and wanted to join them. But, Molly was a mermaid and had to live in the sea.
Every month Molly would watch as a big ship would came to the island to bring boxes. The children took the boxes and gave the sailors bags of coconuts. Molly was so curious that she had to find out what was in the boxes so she swam to the beach and called over to the children, “Hi, land children�!
They were shocked, they had never seen a mermaid before, “What are you?” “I’m a mermaid and I live under the sea. My name is Molly.” She explained. “Hi, I’m Sarah and this is Dane,” Sarah said slowly and kept her distance. “What’s a matter, haven’t you ever seen a mermaid before?” Molly flapped her tail and tumbled in the water. She smiled at them to calm their nerves. “Well no,” said Dane “Why do you have a fish tail?”
“So I can swim like a fish!” She said as she swam in a circle. The children laughed. “Hey Molly, teach us to swim like you do.” “Point your feet and kick!” She showed them how to swim like she did, but they couldn’t keep up with her. Molly was a mermaid and mermaids have arms like a land person but the tail of a fish. Land people had legs for walking but they weren’t very useful for swimming. The land kids tried to keep up but Molly swam fast and could breathe under the water. Soon the kids were tired and asked Molly to sit on the rock with them. Molly told them stories about sharks and jellyfish. “Did you know that sharks are fish and get their oxygen from seawater through their gills?” She told them. “But dolphins are mammals that breathe air just like you.”
The land children listened and learned. “And jellyfish don’t breathe at all, the oxygen just passes through their skin.” “You sure know a lot Molly,” Sarah already considered Molly a friend.
“But I don’t know what is in those bags and boxes that you took off the ship,” Ah, Molly figured out how to ask them what she had been wondering. “Well,” Dane started “Since we don’t have any stores, the ship brings sugar and flour and we give them coconuts. Sometimes they bring clothes and books.” “Books?” Molly’s eyebrows rose, “I love books.” “Well next month the ship will bring lots of them.” Sarah explained “We don’t have a school yet but our parents are going to build a new hut just for the new school.” “That is very exciting.” Molly loved to learn and was already thinking about how she could go to school with the children. “We can’t wait,” Dane smiled. “I’m going to learn all about boats and planes.” “Yes, and I am going to learn about the sea and waves and clouds.” Sarah pointed to the ocean. “I want to learn everything.” Molly laughed. In the distance they heard Sarah’s father calling. “Bye land kids, I have to go now”. Molly didn’t want Sarah’s father to see her. Her mother had always told her to stay away from land people. “Bye Molly,” they said waving goodbye, “come back again.” “Don’t worry, you can count on it.” Molly was so excited about the new school that she couldn’t wait to tell her friends. Molly was a very adventurous mermaid. Most of her sea friends were content just to swim around but not Molly. She was always looking for something to explore. This was the start of a new adventure.
The very next day she asked Dolly to come with her to visit the land kids. Dolly had never seen land kids before so she was eager to see what it was all about. When the kids saw Dolly they jumped into the water and held Dolly’s fin. Dolly swam so fast that the kids had to hold on with two hands. They laughed and yelled, “Faster Dolly, faster”. Dolly chirped with delight, “Molly, now I understand,” Dolly had fun and could see why Molly wanted to play with the kids. “But remember, land people can be very dangerous”. Molly often heard stories about how land people would use big nets and catch fish and sometimes dolphins. When she was a young mermaid her mother told her to stay away from land people. “But Dolly, they are fun and I like them” Molly explained. As the weeks passed Molly and kids became friends. They played together every day and waited for the ship to bring them the new books. “Sarah, do you think I could go to your school too?” Molly asked one day when they were sitting on a big rock near the water. “I don’t see why not,” Sarah wanted Molly to go to school too because they were friends. “But I better ask my parents.”
Later that night Sarah and Dane were eating dinner and they started talking about Molly. Their father laughed when they mentioned that Molly wanted to go to school. “Mermaids don’t go to school!” “But Papa, she wants to go to school to learn,” Sarah said.
“I don’t even want you talking to her”. Her father didn’t understand and thought there was something fishy going on. “But Papa……” Sarah tried to talk but her father cut her off. “Sarah, we don’t know anything about this mermaid. How do we know she is a real mermaid? I’ve never seen one. She might just be dress up like a mermaid and maybe she was sent by pirates to steal our island. “Papa, she is a nice mermaid, won’t you please meet her?” “No Sarah and please stay away from her”. The weeks dragged on. Sarah and Dane wanted to play with Molly but they always listened to their father. They sat on the rock by the water waiting for the ship to bring the books. Sarah and Dane were still excited about the new school but it wouldn’t be the same without Molly. As they sat together, they tried to figure out how they could get their father to allow Molly to go to school with them. “Dane, it’s not fair”, Sarah slammed her fist on the rock. “Ouch, I guess I shouldn’t have done that.” “Sarah, don’t worry, we’ll find a way.” Molly was also trying to think of a way to go to school. She swam just close enough to watch the kids but far enough away that they could not see her. “Dolly, how am I going to get to read the books?” Molly was determined to learn. “I don’t see how you are going to change Sarah’s father’s mind.” Dolly swam close to Molly and nudged her. Molly hugged Dolly and cried.
One summer day Molly and Dolly were swimming and tumbling under the sea, when they heard a big explosion. Molly swam to the surface and poked her head above the water and heard another explosion. Just then Dolly poked her head out of the water. “Dolly, did you hear those two explosions?” She was afraid because she didn’t know what caused the explosion. “TWO, no, I only heard one explosion.” Dolly told Molly “No there were two, I heard them.” Molly insisted “Come on Dolly, we have to figure this out.” Molly started swimming towards where the sound came from. They could see a dark object in the distance. It was a pointed object that looked like it was sticking right out of the ocean. “Look Molly, what is it?” Dolly was afraid but she was very curious.
“It looks like a ship.” The ship was sinking and only part of it was sticking out of the water. As they got closer they saw some land people in a tiny yellow boat. They swam over to them to get a better look. The burly man squinted and rubbed his eyes in disbelief, “Is that a mermaid”? “Mermaid? Have you been drinking salt water?” The other man answered. “It is too a mermaid, you old fool.” He started paddling towards Molly and leaning over the edge almost falling out. Molly wanted to know so she swam up to the land people but kept a safe distance.
“Hi” she said to them. “Well hello there little mermaid” they were shocked to be talking to a mermaid. Leaning over the side of their life raft they tried to paddle over to Molly. “I heard two explosions”, said Molly “Two?” He looked surprised “No there was only one.” The two old gruff men looked at each other. “Come here.” They wanted a better view of a mermaid. Molly backed away. “What happened?” Molly was really confused. She knew she heard two but why did everyone else hear only one? This was a mystery that she had to solve. “We were on our way to the Island of Serenity and the engine blew and the ol’ ship sunk”, they pointed to the island “Now we are stranded, all for a bunch of books”. “Books?” They had finally arrived but now they were sinking to the bottom of the ocean. “Dolly,” she whispered, “we have to get those books. “Molly I’m afraid,” Dolly whispered back. “Shhhh, I’ve got a plan.” Molly whispered. “Oh no, what are you thinking,” Dolly was very afraid. Dolly just wanted to get as far away from the land people as she could. She knew Molly wasn’t about to give up that easily. “We have to get going” Molly told the land people “Good luck getting home”. Dolly and Molly swam as fast as they could. They swam to the bottom of the sea. As they reached the ship their excitement grew. Entering the ship they saw hundreds of books.
“Dolly, which on should we read first?” Molly wanted to get started reading right away. “Molly, what is this one?” Dolly didn’t understand. “Physics” Molly read the title. “Hummm, what does it mean?” She opened the book and read that physics is the science of matter and energy and their interactions. “Matter?” She turned to Dolly, “I HAVE to read this one”. “What’s matter,” she thought to herself. Matter is just stuff. It’s anything that you can see and feel. There are different branches of physics. Mechanics is the study of motion and forces, acoustics is the study of sound, optics is the study of light, thermodynamics is the study of heat and there are many other branches of physics. Molly will someday read all about the other branches. But for now, she will learn all about mechanics, acoustics, optics and thermodynamics. “Energy? That reminds me, if I don’t breathe, I won’t have any energy”. Dolly is a dolphin and dolphins are mammals. Mammals breathe air, unlike fish that extract air out of the water with their gills. Mermaids can breathe air and breathe under the water. As Dolly swam towards the surface, bubbles followed her up. Molly watched, as the bubbles got larger and larger. She wondered why. “Let’s see, bubbles hmm,” as she flipped through the book she saw a picture of a scuba diver. She started to read about water pressure. The water pressure is very strong in deep water and the pressure compresses the bubble. She tried to explain it to Dolly but Dolly just couldn’t understand it.
“Dolly, it’s like this. The bubble is full of air, like a balloon. You know how hard it is to keep a balloon under the water right? That is because the air is lighter than water so it floats up!” “Now I get it” Dolly flapped her fins. “But why do bubbles get bigger as they go up?” “The water pressure is deeper toward the bottom of the sea because there is a lot of water on top of it. The poor little bubble gets squished. But there is less pressure toward the surface. So, the bubble gets bigger as it rises because it is LESS squished!” Molly did her best to explain such a complicated subject. “Cool, I’m going to blow some bubbles and watch them rise!” Dolly started to swim away and Molly followed. “Dolly, lets bring these books to my shell,” Molly lives in a big scallop shell. It was huge and she decorated it with pearls and sea glass. She made a soft bed with seaweed and sponge. She thought about the land children and wished she could bring them the books but she was not allowed to play with them anymore. Their father would not allow it. “Molly, they are not your books, you can’t just take them.” Dolly was very honest. “Dolly, I’m not going to keep them but I’m not allowed near the children remember,” she looked at Dolly with a sad look. “Besides, we can’t just leave them here and we can’t bring them to the children. We’ll just hold on to them until we figure out how to get them to the children.” “Well I guess that’s ok. But we have to tell the children.” “OK we will,” Molly wanted to see the children and this gave her a good reason.
“We could get Ollie to help” Dolly suggested Ollie because Ollie is an octopus. He has eight arms and can carry a lot of books. “Good idea,” she said as they swam off.
They asked Ollie and he asked Fred and Fran Fishes and they asked Sally Seahorse and she asked Larry Lobster. They all wanted to help Molly. Back and forth they went carrying all the books. They piled them high next to Molly’s shell home. On their last trip back to the ship, they saw scuba divers. Fred and Fran were afraid. “What are they?”
“They are land people who dress like fish!” Molly explained. “They wear fins on their feet so they can swim fast like a dolphin.” Molly, Dolly, the fishes Fred and Fran, Ollie the octopus and Larry the lobster all secretly watched the divers. Fred asked Molly why they had big tanks on their back. “Land people can’t breathe underwater like you can Fred. They bring their air with them in those big tanks and the hose goes to their mouth. When they breathe out the air forms bubbles and float to the surface.” Molly told them. “I can tell you all about bubbles!” Dolly excitedly told them. “But how do their fins work?” Ollie didn’t have fins he had eight legs instead!
“When a dolphin pushes their tail downward, the water above their tail moves faster and backward, this pushes the dolphin forward. Then when they move their tail upward, the water below moves faster and backward and again the dolphin is pushed forward.” Molly told them to watch as she pushed her tail downward. They watched as little pieces of seaweed moved faster over her tail. And they saw her move forward. “Let me try,” Dolly pushed her tail down and the same thing happened. “What about us,” Fred said “You and Fran are fishes and your tail moves left and right instead of up and down. But it works the same way. When you push your tail to the left the water flows faster on the right but it still pushes you forward. Then you push your tail to the right and the water moves faster on the left!” Molly laughed. This type of mechanics is known as fluid mechanics. Fluids are things that flow such as water or air. Swimming is like flying. The air or water goes over and under a body. A bird flying through the air is a lot like a dolphin swimming in the water. A bird’s winds go up and down propelling the bird forward and its tail makes it fly straight. A dolphin’s tail goes up and down and its fins keep it going straight.
They worried that the divers were going to take all of the books. But the divers didn’t take the books; they were looking for something else. They were looking for treasures. Molly already found her treasures! Patiently they waited for the divers to leave. They knew that the divers could only stay under the water until their air ran out. Dolly especially knew that. She had to go up for air again. While Dolly swam to the surface, the divers spotted Molly. They couldn’t find any treasures but they found a mermaid. They thought that if they captured a mermaid they would be famous. Signaling each other they grabbed a net and swam over to catch Molly. Molly was too busy telling Fred and Fran all about physics that she didn’t notice the divers sneaking up on her. When she finally noticed, it was too late. The divers threw a big net over her and dragged her through the water. “Stop, stop” yelled Olly. But Olly was a slow swimmer and couldn’t catch up to them. Fran and Fred were too small to do anything to stop them. Sally yelled, “Dolly, you have to stop them.” Larry Lobster jumped on Dolly’s back and Dolly used her strong tail to swim as fast as she could.
“Hurry, catch up to them”, Larry yelled. “I’m trying,” Dolly was swimming as fast as she could. The divers were swimming fast but Dolly is a dolphin and dolphins are very powerful, strong swimmers. It didn’t take long for Dolly to catch up to the divers. When she did, Larry snipped the net with his powerful claws. Molly swam through the hole in the net. “Get them Dolly”, Larry yelled. Dolly butted them with her head and they tumbled. As they tumbled big bubbles floated to the surface. “Let’s get out of here before she hurts us,” the diver yelled. “YEAH get lost”, Dolly yelled to them. Molly held on to Dolly as they swam to safety. She was exhausted. “Molly, come with me, I know a spot we can relax”, Dolly knew she needed rest. They went to the cove so Molly could rest. Molly rested in the shallow water. “Dolly, I’m not supposed to be near the children. Their father won’t allow it.” “Molly, you are exhausted. They will just have to understand.” Dolly swam close by to make sure no one bothered Molly. Just then the children showed up. “Molly what’s the matter?” “Dolly and Larry rescued me from the divers. They put a net over me and were going to take me.” Molly told them. “Are you ok?” Sarah ran to Molly and held her hand. Dane started to cry. “I’m so sorry that we are not allowed to play together. I miss you so much.” “Dane, don’t cry. It will be alright.” Molly hugged him. From the distance they heard their father’s voice, “Sarah, Dane what is going on?”
“Papa, it’s Molly, she needs us,” Sarah yelled back. Sarah’s father ran over to see what was going on. “Papa the divers tried to take her,” Sarah was so afraid that she started to cry. “Don’t worry Sarah I’ll protect all of you.” He said as he sat by Molly. Molly didn’t know where to start. She told him about the ship sinking and how she found all the books at the bottom of the sea. She apologized for taking the books. Sarah’s father smiled. He could see that Molly really was a nice mermaid. He felt bad that he wouldn’t allow her to play with the kids. She was a kid too, a kid mermaid! “That’s ok, the books are ruined because they are wet. You can keep them.” Sarah’s father finally understood why the children loved Molly.
“I learned a lot from those books.” Molly told them. “Teach us,” the children sat in the warm shallow water. “Well, I can teach you why the water is so warm on the surface and why it is colder the deeper you swim.” Molly smiled. “Tell us Molly.” “It’s because of thermodynamics.” “Boy you are a smarty pants!” Sarah’s father looked at Sarah and raised his eyebrow as he smiled. He also wanted to learn. “You see, the Sun shines its light on the water and the water absorbs the Sun’s energy. The sun is like a big ball of fire. The heat from the Sun travels to the Earth and warms whatever it shines on. Just like when you stand in front of a fire. You feel the heat on your face but not on your back.
The heated water is less dense, which means that it weighs less than colder water. Since it is lighter it will remain on the surface. “Very interesting� Dolly was learning so much.
This method of heat transfer is called radiation. The heated water then transfers heat to the colder water, which is called conduction, and when the warm water flows upward, like when you boil water in a pot, it is called convection. Warm water will stay on the surface because it is less dense. The water was as blue as the sky and smooth as glass. You could see right down to the bottom. They floated quietly, when Dolly noticed Molly’s arm. “Molly why is your arm bent?” Dolly saw that Molly’s arm look like it was bent in the water. “What do you mean bent?” Molly didn’t know what Dolly was talking about. “It doesn’t look straight”. “Oh, that’s because of the index of refraction.” Molly read about optical illusions. Her arm was really straight but it looked bent because of refraction. The light bounces off the object towards your eye. Depending on what the light is traveling through, the light will bend slightly. Water is thicker than air so the light will bend more than when it travels through the air, so the part of the arm that is in the water will appear bent.
The bending of light is called refraction. The amount of bending is called the index of refraction. When light shines on water, some of the light will reflect and some of the light will refract. When light hits a mirror, all of the light is reflected. “Molly, we had quite a day.” Dolly was tired too. “Yes we did.” Molly smiled “we learned a lot today.” One of the books was about acoustics. Molly taught the children that sound moves faster in water than through the air. And dolphins use sound waves to “see” their surrounding. When they send out a sound, it bounces off the bottom of the sea or a fish, and they can tell how far away things by how long the sound takes to come bounce back. Molly figured out why she heard the explosion twice! Sound travels slower through the air. The first explosion was heard under the water and then the same explosion was heard a second later when she popped her head out of the water. “And thermodynamics when the water was so warm at the surface.” Molly chirped back. “And bent arms, I mean optics.” “But most of all we learned to stay away from diver strangers.” Molly didn’t ever want to be in that situation again. “Don’t forget mechanics!” Dolly loved learning about swimming and how her tail worked. “If it wasn’t for mechanics, I would have never caught up to those divers. I hate to think what could have happened.”
“Thank you Dolly.” Just then the land children ran to the edge of the water. “Hi Molly, come swim with us.” Molly looked at Dolly and laughed, “I’m too tired right now, how about tomorrow?”
“Will you tell us a story tomorrow?” “I’ll tell you lots of stories tomorrow” Molly smiled. She had a lot to teach them. Dolly splashed and did a flip. The day was over and it was time for Molly to return to her shell and go to sleep. Tomorrow would come quickly and Molly would start another adventure.