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How can the sky be blue one day and stormy the next? Why do heavy objects tend to fall downwards when dropped? How are birds able to fly (and why can’t I do the same?)? Human beings have long been curious about the world in which we live, striving to identify connections among the phenomenons we witness and to understand how it all works. The field of science has developed over many centuries as a way of studying and understanding the world, beginning with the primitive stage of simply noting important regularities in nature and continuing through the rise of modern science. The modern-day sciences cover a vast range of fields, including biology, chemistry, meteorology, astronomy, physics, and much more. Browse Subcategories Astronomy Biology Birds, Reptiles & Other Vertebrates Bugs, Mollusks & Other Invertebrates Chemistry Earth Science, Geologic Time & Fossils Environment Mammals Mathematics Plants Physics

Featured content, July 03, 2020

What Makes a Species Endangered? Prepare to feel a little guilty. Demystified / Science Written By Jonathan Hogeback 10 Deadly Animals that Fit in a Breadbox Tiny terrors of the animal kingdom. #WTFact / Science Written By Alison Eldridge Uninvited Guests: The 7 Worst Parasitic Worms That feeling inside… List / Science Written By Richard Pallardy The Solar Eclipse That Made Albert Einstein a Science Celebrity How an eclipse tested the theory of general relativity. Spotlight / Science The Anthropocene Epoch: Adding Humans to the Chart of Geologic Time On August 29, 2016, the Anthropocene Working Group recommended that the Anthropocene Epoch be made an official geologic unit. Companion / Science Written By John P. Rafferty Climate change Climate change, periodic modification of Earth’s climate brought about as a result of changes in the atmosphere as well as... Encyclopedia / Science Written By Stephen T. Jackson Climate Climate, conditions of the atmosphere at a particular location over a long period of time; it is the long-term summation... Encyclopedia / Science Written By Basil John Mason | See all Metabolism Metabolism, the sum of the chemical reactions that take place within each cell of a living organism and that provide energy... Encyclopedia / Science Written By Hans Kornberg

Science Quizzes

Human Skin: Fact or Fiction? Is acne caused by chemical changes in the body? Are differences in skin color related to pigment? Unclog your mental pores... Quiz / Science The Human Experience: Fact or Fiction? Does human hair grow faster in the summer or in the winter? Are most human babies born on their exact due dates? Learn more... Quiz / Science Ancient Life: Fact or Fiction? From Neanderthals to ancient Egypt, explore early human life in this quiz. Quiz / Science Optics: Fact or Fiction? Does sound travel faster than light? Does each color of light have its own wavelength? Sort fact from fiction--and light... Quiz / Science Vipers, Cobras, and Boas...Oh My! What is the world’s longest poisonous snake? To which continent are rattlesnakes native? Learn more about these limbless... Quiz / Science Bats: What Vampires Don’t Want You To Know Do you know what bats use to control their wings? Learn about the natural habitats and characteristics of these flying mammals... Quiz / Science Best In Show How many breeds of dogs are there? What is the largest terrier? Learn more about "man’s best friend" in this quiz dedicated... Quiz / Science Dog Fun Facts Quiz How many bones are in a dog’s spine? Which sense does a dog lack? Learn these facts and more by taking this quiz. Quiz / Science A Little Bird Told Me How many eggs do vultures lay? What grows over a turkey’s beak? Explore the lives and capabilities of birds from around the... Quiz / Science The Bug-Eyed Quiz What is the name for an insect’s egg-laying organ? How many known species of insects are there? You may be surprised by what... Quiz / Science

Science Videos

Discover how bacteria evolved to survive in Earth's most-extreme habitats such as seafloor volcanic vents Video / Science See how water transforms between liquid, ice, and vapour in the water cycle Video / Science Watch human immune response phagocytosis in which granular leukocyte consumes bacteria Video / Science Observe a trumpeter swan care for cygnets in their nest and marsh-grass habitat Video / Science Learn how phytoplankton supply oxygen via photosynthesis and serve as the first step in the marine food chain Video / Science Uncover the forces of potential energy, kinetic energy, and friction behind a grandfather clock's pendulum Video / Science See molecular bonds at work as two hydrogen atoms join a sulfur atom to make hydrogen sulfide Video / Science Watch mating display of Anna's hummingbird and how hens use food to coax fledglings to fly Video / Science See stalagmites and stalactites formed by carbonite mineral deposits from limestone dissolved by groundwater Video / Science Consider whether the continuous band of membranous tissue around humans' intestines should be deemed an organ Video / Science Image Gallery Science View Gallery Never Miss a Day in History Sign up for daily fun facts about this day in history, updates, and special offers delivered right to your inbox. Thank you for subscribing! Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox.

Science Subcategories

Astronomy Human beings have always been fascinated by the celestial sphere above, whose twinkling lights have inspired many theories and artistic endeavors. Study of the solar system has provoked more than just peaceful meditation, however; a major controversy among astronomers arose in the 16th century when Copernicus publicly championed heliocentrism, a Sun-centric model of the solar system that was in direct opposition to Ptolemy's Earth-centered model, which had been generally accepted from the 2nd century CE onward. But humankind's fascination with the world beyond Earth has also led to some landmark moments in history, as when space exploration took a giant step forward with the advent of technology that allowed humans to travel to the Moon and to build spacecraft capable of exploring the rest of the solar system and beyond. Articles Biology If it’s alive, biology will define it, study it, observe all its functions, follow its vital processes, and interact with it, all in order to understand the life that animates it. In one of biology's best-known examples of such studious investigation, Charles Darwin came up with his scientific theory of evolution by natural selection after systematically observing a variety of plants and animals; his work acted as the foundation upon which modern evolutionary theory is built. But biology’s principles also operate within a plethora of other related fields, including biochemistry, biomedicine, biophysics, and microbiology. Articles Birds, Reptiles & Other Vertebrates Although it can be hard to imagine that a peacock and a crocodile have much of anything in common, these animals are actually descendants of the same prehistoric vertebrates. Birds are thought to have descended from carnivorous dinosaurs that began growing feathers by the Late Jurassic Period; thus, birds are technically one lineage of reptiles. This evolutionary link highlights the way in which seemingly incongruous creatures can, in fact, share a common ancestor (though that doesn't mean that we should expect waterfowl and crocodiles to become friends anytime soon). Articles Bugs, Mollusks & Other Invertebrates Some insects are so displeasing to humans that the word "bug" has come to be used as a verb meaning "to bother or annoy." Yet, in addition to being critically important—because they naturally recycle decaying matter—in maintaining balance within the food chain, bugs can also be fascinating creatures, whether in regard to the water strider's ability to run across the surface of water or in regard to assassin bugs' varied and creative means of catching and killing their prey. Mollusks, another group of invertebrates, get less of a bad rap. Their ranks include nearly 100,000 described species of soft-bodied animals that are usually wholly or partly enclosed in a calcium carbonate shell; examples include snails, clams, oysters, squids, and octopuses. Articles Chemistry How do you use raw plant materials to manufacture a best-selling perfume? How do you engineer household products that are compliant with environmentally-oriented guidelines? The answers to these questions require an understanding of the laws of chemistry, the science that deals with the properties, composition, and structure of elements and compounds, as well as the transformations that such substances undergo and the energy that is released or absorbed during those processes. Chemistry is also concerned with the utilization of natural substances and the creation of artificial ones. Over time, more than 8,000,000 different chemical substances, both natural and artificial, have been characterized and produced. Chemistry's vast scope comprises organic, inorganic, physical, analytical, and industrial chemistry, along with biochemistry, environmental chemistry, medicinal chemistry, and much more. Through the dedicated efforts of people such as Robert Boyle, Dmitri Mendeleev, John Dalton, Marie Curie, and Rosalind Franklin, the field of chemistry has led to exciting innovations as well as crucial advances in our understanding of how the world functions, starting with just the miniscule and unassuming atom. Articles Earth Science, Geologic Time & Fossils Planet Earth has billions of years of history, from the time when it was an inhospitable ball of hot magma to when its surface stabilized into a variety of beautiful and diverse zones capable of supporting many life-forms. Many are the species that lived through the various geologic eras and left a trace of their existence in the fossils that we study today. But Earth is never done settling, as we can see from the earthquakes, tsunamis, volcanic eruptions, and other phenomena manifested in Earth’s crust, oceans, and atmosphere. Articles Environment Biological diversity is key to a healthy ecosystem, whether it’s a small biological community or the global biosphere. Ecology, which studies the relationships between organisms and their environment, is an invaluable science that helps us understand what allows an ecological community to thrive. Articles Mammals These are the animals to which humans tend to relate the most, perhaps because aspects of their behavior can sometimes resemble the way that we ourselves behave. The protective instinct of a mother bear, the gamboling way that kittens play, and the loyalty displayed by a dog are all traits that we can identify with in the course of our own lives. Mammals are well-equipped to handle different climates and biomes because of their ability to regulate their own body temperatures and internal environment, both in excessive heat and aridity and in severe cold. Articles Mathematics Although stock portrayals of mathematicians often involve a studious person standing in front of a chalkboard that's covered with mind-bogglingly complex scrawled mathematical problems (call it the "Good Will Hunting" effect), the chaotic-looking equations may obscure the fact that mathematics is, at its heart, a science of structure, order, and relation that deals with logical reasoning and quantitative calculation. There's a method to all that madness! The history of mathematics can be traced back to ancient Mesopotamia, whose clay tablets revealed that the level of mathematical competence was already high as early as roughly the 18th century BCE. Over the centuries, mathematics has evolved from elemental practices of counting, measuring, and describing the shapes of objects into a crucial adjunct to the physical sciences and technology. Articles Plants Life on Earth owes much to plants. The vast majority of plants carry out photosynthesis to transform light energy into chemical energy, which is the way that virtually all energy in the biosphere becomes available to living things (including us humans). As photosynthetic organisms, plants occupy the base of Earth's food webs and are consumed directly or indirectly by all higher life-forms, thereby functioning as the major source of food for humans and other animals. Plants' photosynthetic activity also produces the air that we breathe: almost all the oxygen in the atmosphere is due to the process of photosynthesis. Still not convinced about the merits of plants? Consider the fact that many plants not only serve up crucial nutrients and breathable air but also look good doing it. Many plants are admired for their striking aesthetic qualities, and flowers such as tulips, lilies, sunflowers, and daisies beautify fields, gardens, windowsills, and bouquets the world over. Plants are also a primary source of consumer goods, such as building materials, textile fibers, and pharmaceuticals. Articles Physics What’s the matter? The matter is our whole observable universe—with that material substance that constitutes it—and it is the subject of study of physics. The laws that govern motion observed by Newton, the gravitational force that regulates the progress of all celestial bodies, the interaction between subatomic particles, and the nuclear engineering that created the atomic bomb are examples of what this important discipline is all about. Minkowski’s space-time concept, which reformulated Einstein’s special theory of relativity, has bridged physics with philosophy in a conversation that has fascinated the modern concept of physics. 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