Science & Tech
7 Drugs that Changed the World
Only a small number of substances could be said to have fundamentally revolutionized medicine.
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History of Artificial Intelligence
It has existed for less than a century but artificial intelligence has evolved rapidly, and keeps evolving.
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Editor's Picks
How Much Water Should a Person Drink in a Day?
The popular recommendation to drink 8 cups of water every day isn’t as definitive as it may seem. The amount of water one should drink depends on a number of factors, including age, biological sex, and activity level. On average, women need to consume about 11 cups (2.7 liters) of water (the U.S.
epistemology
Epistemology, the philosophical study of the nature, origin, and limits of human knowledge. The term is derived from the Greek epistēmē (“knowledge”) and logos (“reason”), and accordingly the field is sometimes referred to as the theory of knowledge. Epistemology has a long history within Western
How Fast Is the Universe Expanding?
The rate at which the universe is expanding is called the Hubble constant, named after astronomer Edwin Hubble, who, with Milton Humason, showed convincingly that the velocity with which a galaxy was moving away from Earth was proportional to its distance. That is, velocity = Hubble constant ×
6 Amazing Facts About Gravitational Waves and LIGO
Nearly everything we know about the universe comes from electromagnetic radiation—that is, light. Astronomy began with visible light and then expanded to the rest of the electromagnetic spectrum. By using the spectrum, from the short wavelengths of gamma rays to the long wavelengths of radio waves,
nanotechnology
Nanotechnology, the manipulation and manufacture of materials and devices on the scale of atoms or small groups of atoms. The “nanoscale” is typically measured in nanometres, or billionths of a metre (nanos, the Greek word for “dwarf,” being the source of the prefix), and materials built at this
6 Questions About DNA Answered
Deoxyribonucleic acid, better known as DNA, is crucial to life on Earth. The questions and answers in this list are taken from the Top Questions sections of the articles on DNA, recombinant DNA, and chloroplast, where you can find more questions answered. list, DNA, deoxyribonucleic acid,
deepfake
Deepfake, synthetic media, including images, videos, and audio, generated by artificial intelligence (AI) technology that portray something that does not exist in reality or events that have never occurred. The term deepfake combines deep, taken from AI deep-learning technology (a type of machine
What Causes the Northern and Southern Lights?
The auroras—the aurora borealis (or northern lights) in the Northern Hemisphere, and the aurora australis (the southern lights) in the Southern Hemisphere—are brilliant natural spectacles that can be seen in the evening sky especially at higher latitudes. Unlike other phenomena of the night sky,
Spotlight: Mummification
A team of scientists recently recreated the face of Peru's most famous mummy, "Juanita," or the "Ice Maiden." The girl is thought to have been sacrificed when she was between the ages of 13 and 15 some 500 years ago. Mummified by centuries of ice and snow, the body was well-preserved and is just one example of how mummification can occur naturally.
Quizzes
Name That Magnified Object!
Can you figure out what these common items are when they're extremely magnified?
Guess the Body Part Quiz
Taking this quiz requires guts.
Name That Thing: Science
Do you know the difference between a protractor and a compass?
Guess the Animal Eyes Quiz
Can you tell these creatures just by looking at their peepers?
Videos
How volcanoes work, explained by a volcanologist
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Featured Categories
Biology
6 Cell Organelles
Think back to your high school biology class. Do you still remember the names and functions of all those little cell parts? A little foggy on the details, perhaps? Here’s a quick refresher course of some of the major eukaryotic organelles to keep your science skills sharp. It might come in handy
How Does the Human Body Maintain Its Temperature?
People are mammals, and mammals are warm-blooded creatures, capable of maintaining a relatively constant internal temperature regardless of the environmental temperature. Body temperature control is one example of homeostasis—an organism’s self-regulating process that tends to maintain internal
10 Ways of Looking at Cells
Since 1665, when English physicist Robert Hooke coined the term cell to describe the microscopic view of cork, scientists have been developing increasingly sophisticated microscopy tools, enabling them to view ever-smaller details of cellular structure. Far from the poor-quality microscopes that
13 Questions About How the Human Body Works Answered
How do people breathe in and out? What’s the body’s biggest organ? What causes a bruise? This list answers these questions and others about how the human body works. Earlier versions of these questions and answers first appeared in the second edition of The Handy Answer Book for Kids (and Parents)
Astronomy
9 Ghostly Planets
Humanity has sent probes to every planet, so we now have a decent idea of what’s in our neighborhood. Even before that, astronomers tracked the movements of the solar system for millennia. Sometimes their eyes (or brains) played tricks. Or did they? What ever happened to the ghost planets, those
Why Are Planets Round?
The Sun and all eight planets of the solar system are round. Why? The gravitational force of a planet’s mass pulls all of its material toward the center, smoothing out any jarring non-roundness. Many of the smaller bodies of the solar system are not round because their gravity is not enough to
How Fast Is the Universe Expanding?
The rate at which the universe is expanding is called the Hubble constant, named after astronomer Edwin Hubble, who, with Milton Humason, showed convincingly that the velocity with which a galaxy was moving away from Earth was proportional to its distance. That is, velocity = Hubble constant ×
Telescopes: Seeing Stars
Recently the world’s largest single-dish radio telescope was completed in China. The Five-hundred-metre Aperture Spherical radio Telescope (FAST) is, as its name says, 500 meters (about 1,600 feet) across, which makes it 2.5 times larger than the previous largest single-dish radio telescope, the
Mathematics
al-Khwārizmī
Al-Khwārizmī was a Muslim mathematician and astronomer whose major works introduced Hindu-Arabic numerals and the concepts of algebra into European mathematics. Latinized versions of his name and of his most famous book title live on in the terms algorithm and algebra. Al-Khwārizmī lived in
Unusual Counting Systems
In our everyday lives, we use a counting system in which we count from 1 to 10. That seems only logical because our hands are already in what is called base 10, which means the number 10 serves as the base of our number system. Each place in a number corresponds to a different power of 10. For
Euclid
Euclid was the most prominent mathematician of Greco-Roman antiquity, best known for his treatise on geometry, the Elements. Of Euclid’s life nothing is known except what the Greek philosopher Proclus (c. 410–485 ce) reports in his “summary” of famous Greek mathematicians. According to him, Euclid
Aryabhata
Aryabhata was an astronomer and the earliest Indian mathematician whose work and history are available to modern scholars. He is also known as Aryabhata I or Aryabhata the Elder to distinguish him from a 10th-century Indian mathematician of the same name. He flourished in Kusumapura—near