Ancient astronomers looked at movements in the sun, moon, and stars to guide travelers and keep track of the seasons. Nicholas Copernicus was the first to challenge people's beliefs that Earth was the center of the solar system and is known as the founder of astronomy. Galileo Galilei built a telescope and spotted craters on the moon and sunspots on the sun. Isaac Newton invented the reflecting telescope and discovered the law of gravity. Astronomers continue to work every day to uncover the mysteries of the universe.
Rachel Carson began writing about nature when she was just 10 years old. She became a zoologist in 1932 and went to work for the United States government as a biologist and writer. She wrote about natural resources and encouraged others to care for the planet. She wrote books that helped people understand the world around them. Everyone can play a part in keeping the Earth healthy.
Everything around us is made up of matter. Understanding how matter can change properties and how the position of molecules determines the state of matter helps explain everything from energy to why certain substances have chemical reactions when mixed together.
Planck studied physics, the science of matter and energy. He wound up making big discoveries in the area of thermodynamics, which is the study of heat and how it moves. Planck won the Nobel Prize for his work in Quantum Physics, which is the movement inside of atoms. It changed the way scientists understood the world.
Marie Curie's work in radioactivity changed the way scientists think about matter and energy and led to advancements in the treatment of disease. With her fellow scientist and husband, Pierre Curie, she searched for the source of radioactivity and discovered two elements, radium and polonium. They shared the 1903 Nobel Prize, the world's highest science award, for their discovery.
Energy is all around usâ€”humans use energy, machines use energy, and heat and power use energy. Energy is found in many forms, and there are many energy sources. People are working to develop new, renewable sources of energy for future generations.
Forces can't be seen, but without them, nothing around us would happen! A force is a push or pull that usually causes movement. Friction is a force that opposes motion and slows things down or stops them. Famous scientist and mathematician Sir Isaac Newton wrote the rules about forces and motion.
Light and sound are two of the most important ways to understand the world around us. The sun is Earth's main source of energy and light. Light bounces off objects and travels to our eyes. Our eyes and brain work together to translate that light into what we see while our ears pick up sound vibrations and translate them into meaningful messages.
Scientists who have studied light and sound over the last few centuries invented many things that we still use today. Thomas Young, for example, proved that light moves in waves and invented prescription eyeglasses. The study of sound has led to inventions like the telephone and hearing aids. Thomas Edison studied both light and sound and invented such things as a long-lasting light bulb, the phonograph, and the first recording machine.
There are 90 different elements, like the oxygen that we breathe, that can be found in nature. When two or more elements combine, they are held together by a chemical bond and form a compound. In 1869, chemist Dmitri Mendeléev organized the elements into a chart that is known as the Periodic Table of Elements.
Cells are the building blocks of life. According to Cell Theory, all living things are made of cells; cells are the basic unit of life; and all cells come from other cells. The nucleus of a cell has chromosomes made of DNA, which make each individual unique.
British scientist Robert Hooke built an early microscope and was the first scientist to observe cells and give them their name. Anton van Leeuwenhoek created the best microscopes of his time and used them to study living organisms. Matthias Schleiden, Theodor Schwann, and Rudolf Virchow created Cell Theory, which says that all living things are made of cells; cells are the smallest part of a living thing; and all cells come from other cells.
Many organisms are multicellular, which means they have many cellsâ€”even trillions! The cells work together to help the organism do things such as create energy, reproduce, and get rid of waste.
For many centuries, scientists believed there were only two kingdoms, or groups of living things: plants and animals. But Anton van Leeuwenhoek made microscopes in the 17th century that also proved there are microorganisms, or microbes. Microbes can help keep people stay healthy, but some also can make people sick.
All plants need sun, water, air, and food to grow. Plants are anchored to the ground by their roots, which take in nutrients from the soil. Stems and stalks hold up plants and give them shape, and also hold the plumbing system of the plant. Leaves are the place where food is made for the plant. Many plants make crops for us to eat.
George Washington Carver was born a slave, but he became an important scientist and teacher. He experimented with soil and became famous for his work as a botanist. He used peanuts and other plants to make new products. Before Carver's research, plants were only used for food and clothing. His creative approach to agriculture taught people that plants could be used to make many products, like rubber, ink, fuel, and paper, to name a few.
Plants and animals that need one another in an environment form an ecosystem. All ecosystems have energy pyramids that show the exchange of energy from one food source to another. Biomes are areas of the Earth that have their own climate and characteristics. Ecosystems all over the world are in danger due to pollution, hunting, and other factors. By conserving water, recycling, and reducing pollution, we can help protect Earth's ecosystems and biomes.
Ecologists study the connections living things have with one another and their surroundings. John Woodward did some of the first ecology experiments in 1699 and figured out algae bloom. Aldo Leopold's work led to the Endangered Species Act to protect plants and animals from becoming extinct, and he led the U.S. government to begin considering the environmental impact of land use. Eugene Odum was the first to see Earth as a set of interlocking ecosystems. His work led to laws to protect wetlands.
What things do all animals have in common? How do scientists classify animals? How are humans classified and what makes them different? Enter the animal kingdom with zoologists who study animals! You'll explore how scientists use a system called taxonomy to classify and organize different kinds of living things as you explore the wonderful world of animals.
Jane Goodall is the world's leading authority on chimpanzees. She moved to the African jungle to study them. Her visit to Kenya led to a meeting with famous paleontologist Louis Leakey. Although she wasn't a trained scientist, Goodall began working with Leakey in 1960. She earned the trust of the apes and observed their social interactions. She studied them for more than 30 years. She learned that chimps use tools and are more intelligent than was previously thought.
To understand why humans are the way they are, look at cellsâ€”especially the material in the center, called chromosomes. People have 23 pairs of chromosomes, so each cell has 46 in all. Parents pass chromosomes to their children. DNA carries the genetic information in alleles and is the blueprint for the cells of an organism. DNA tells one's body how to put certain materials together to produce certain traits.