Science & Tech
![Periodical Cicada, Adult, Magicicada spp. Requires 17 years to complete development. Nymph splits its skin, and transforms into an adult. Feeds on sap of tree roots. Northern Illinois Brood. This brood is the largest emergence of cicadas anywhere](jpg/periodical-cicada0d31.jpg)
Why Do Some Cicadas Appear Only Every 17 Years?
You already know why cicadas are so unbelievably noisy. But why do some of them appear aboveground only every 17 years?
© Ed Reschke-Stone/Getty Images
![Brain illustration](jpg/brain-illustration0d31.jpg)
© V. Yakobchuk/Fotolia
Do We Really Use Only 10 Percent of Our Brain?
It’s one of Hollywood’s favorite bits of pseudoscience: human beings use only 10 percent of their brain.
© V. Yakobchuk/Fotolia
Editor's Picks
![Above the clouds 130 nautical miles below, astronaut Mark C. Lee floats freely without tethers as he tests the new Simplified Aid for Extravehicular Activity (EVA) Spacewalk Rescue (SAFER) system, Sept. 16, 1994. Space Shuttle Discovery, STS-64](jpg/mark-c-lee-extravehicular-activity-spacewalk-rescue-sept-16-19949a9f.jpg)
Gravity: From Apples to the Universe
How our ideas of gravity have changed from Aristotle to the present day.
![conversation with ChatGPT](jpg/chatgpt-conversation-encyclopedia-article9a9f.jpg)
ChatGPT
ChatGPT, software that allows a user to ask it questions using conversational, or natural, language. It was released on November 30, 2022, by the American company OpenAI and almost immediately disturbed academics, journalists, and others because of concern that it was impossible to distinguish
![illustration of the walking titanosaurus, Patagotitan mayorum](jpg/patagotitan-mayorum-titanosaurs9a9f.jpg)
Titanosaurs: 8 of the World's Biggest Dinosaurs
The largest land animals of all time.
![Lightning over a farm field. Weather electricity thunderstorm light energy tree](jpg/lightning-farm-field-energy-tree-weather-electricity9a9f.jpg)
Can Lightning Strike the Same Place Twice?
Does this common phrase hold any truth?
![A human Inuit skull in a stone chambered cairn in Ilulissat in Greenland. These ancient graves are pre christian and are at least 2000](jpg/human-inuit-skull9a9f.jpg)
What Happens to Our Bodies After We Die?
What happens to our bodies after we die isn’t a mystery, but it might turn your stomach.
![In this aerial photo, structures are damaged and destroyed October 15, 2005 in Balakot, Pakistan. It is estimated that 90% of the city of Balakot was leveled by the earthquake. The death toll in the 7.6 magnitude earthquake that struck northern Pakistan on October 8, 2005 is believed to be 38,000 with at least 1,300 more dead in Indian Kashmir. SEE CONTENT NOTES.](jpg/damage-balakot-pakistan-due-to-earthquake-october-8-2005-kashmir9a9f.jpg)
6 of the World’s Deadliest Natural Disasters
This list compiles six of the deadliest natural disasters in world history.
![Nikola Tesla](jpg/nikola-tesla9a9f.jpg)
Nikola Tesla
Nikola Tesla Serbian American inventor and engineer who discovered and patented the rotating magnetic field, the basis of most alternating-current machinery. He also developed the three-phase system of electric power transmission. He immigrated to the United States in 1884 and sold the patent
![Dr. Maria Telkes, September 4, 1956.](jpg/maria-telkes9a9f.jpg)
10 Women Scientists Who Should Be Famous (or More Famous)
History has overlooked some awesome women for too long.
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
![Human eyelashes under magnifcation. Colored scanning electron micrograph (SEM) of human eyelash mites](jpg/human-eyelashes-scanning-electron-micrograph9a9f.jpg)
Name That Magnified Object!
Can you figure out what these common items are when they're extremely magnified?
![3d illustration of small intestines, human body, anatomy](jpg/anatomy-small-intestine9a9f.jpg)
Guess the Body Part Quiz
Taking this quiz requires guts.
![Name that Thing - Science, composite: circuitboard, gnomon, eye iris, airplan yaw](jpg/name-that-thing-science-composite9a9f.jpg)
Name That Thing: Science
Do you know the difference between a protractor and a compass?
![Close up of the eye of a horned owl. (genus Bubo) bird raptor. Cropped version of Asset ID:](jpg/close-up-of-the-eye-of-a-horned-owl9a9f.jpg)
Guess the Animal Eyes Quiz
Can you tell these creatures just by looking at their peepers?
Videos
![How volcanoes work, explained by a volcanologist](jpg/what-are-volcanoes-lava-flows.jpg)
How volcanoes work, explained by a volcanologist
Encyclopædia Britannica, Inc.
Galleries
![Paricutin Volcano, Mexico, in eruption at night. 1947.](jpg/paricutin-volcano-mexico.jpg)
7 Wonders of the Natural World
![Nickel-iron meteorite, from Canyon Diablo, Arizona.](jpg/meteorite-arizona-canyon-diablo.jpg)
Meteorites
![Orange Cup Coral](jpg/corals.jpg)
Coral
![Reed frog on the inside of a pink lily flower (hyperolius sp)](jpg/frog-lily.jpg)
Life
![With the tornado in the background in Goshen County, Wyoming on June 5, 2009, the National Severe Storms Laboratory Field Command Vehicle helped coordinate operations in the field during the Verification of the Origins of Rotation in Tornadoes Experiment](jpg/national-severe-storms-laboratory-field-command-vehicle.jpg)
Tornadoes
![Milky Way galaxy in night sky. (space, stars, center, astronomy, telescope)](jpg/night-sky-milky-way-galaxy.jpg)
The Solar System
Featured Categories
Biology
6 Cell Organelles
A quick refresher course in biology!
How Does the Human Body Maintain Its Temperature?
Human body temperature is regulated by the hypothalamus in the brain.
10 Ways of Looking at Cells
Learn about 10 cutting-edge microscopy tools that scientists are using to explore the internal structure of cells.
13 Questions About How the Human Body Works Answered
Blood, brains, lungs, skin, and more.
Astronomy
9 Ghostly Planets
Were they ever out there to begin with?
Why Are Planets Round?
There are a lot of strange things in the universe, so why are planets round instead of every shape imaginable?
How Fast Is the Universe Expanding?
Learn why the Hubble constant doesn’t seem to be very constant.
Telescopes: Seeing Stars
For the last 400 years, telescopes have changed our view of the universe.
Mathematics
al-Khwārizmī
Al-Khwārizmī 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 Baghdad,
Unusual Counting Systems
In everyday life we use a base-10 counting system, but that is not something that has always been used in history.
Euclid
Euclid 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 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 Patalipurta