Science · Nature · History
17 fascinating things worth knowing
Why is the sky blue? How does your phone know where you are? Why did the Mississippi run backward in 1812? How do you keep a family talking when the phones go down? These short lessons answer seventeen questions worth wondering about, from the Moon overhead to the moss on the roof.
Each topic opens a page with four parts:
Each topic also comes as slides (PDF), a Word document for printing and a PowerPoint. Your best test score is saved on your own device and shows beside each topic.
Seventeen topics, about ten minutes each. Start anywhere, or open them all in one page.
Open all 17 topics in one page Explore The Big Questions: 25 more topicsWhen the power goes out and the cell towers go quiet, a GMRS radio in every pocket keeps a family together. How to get the $35 license that covers the whole family with no test, how to talk on the radio, how to pick family channels, and how far a handheld really reaches. For more, open the full 15-lesson GMRS series.
When the phones go down, ham radio connects your family to repeaters, weekly nets and emergency volunteers across the region. How the Technician test works, what the $35 license costs, why each family member needs their own, how to use a repeater and how far a ham radio really reaches. For more, open the full 15-lesson Ham series.
Sunlight looks white but carries every color of the rainbow, and the air itself scatters the short blue waves across the whole sky. Why the sky isn't violet, why sunsets turn red and orange, and why the sky on Mars runs the other way, with butterscotch days and blue sunsets.
Your phone finds itself by timing radio signals from satellites more than 12,000 miles up. Why it takes at least four satellites, how atomic clocks make it work, and why GPS would drift off by miles every day if engineers hadn't corrected for Einstein's theory of relativity.
Tardigrades are tiny eight-legged animals, smaller than a grain of salt, that live in moss and puddles nearly everywhere. They can dry up into a lifeless-looking husk, survive deep cold, crushing pressure and radiation, and even outer space, then come back to life with a drop of water.
Light moves about 186,000 miles every second, fast enough to circle the Earth seven times in a blink. Yet sunlight is already eight minutes old when it reaches you, and some starlight left before people existed. How a light-year works and how far away our neighbors in space really are.
A honeybee hive is a city of tens of thousands of sisters run by a single queen. Bees give each other directions to flowers by dancing, and a worker makes only a tiny drop of honey in her whole life. Why honey can keep for centuries, and how much flying goes into one jar.
Almost every substance shrinks and sinks when it freezes, but water does the opposite. Learn why ice floats, why lakes freeze from the top down and keep fish alive all winter, why pipes burst in a freeze, and why about 90 percent of an iceberg hides underwater.
Your heart beats about 100,000 times a day, your blood vessels would stretch more than twice around the Earth, and you're made of roughly 37 trillion cells, with about as many bacteria along for the ride. Fun numbers about bones, blood, skin and the parts that quietly rebuild themselves.
Octopuses have three hearts, blue blood and about two-thirds of their brain cells in their arms. They change color in a blink, even though they probably can't see color, squeeze through any hole bigger than their beak, and solve puzzles, all in a life that usually lasts only a year or two.
The Pantheon in Rome has stood for about 1,900 years and still has the world's largest unreinforced concrete dome. Learn the Roman recipe of lime and volcanic ash, the self-healing trick scientists figured out in 2023, and why Roman sea walls grew stronger in salt water while modern concrete cracks in decades.
In the winter of 1811 and 1812, three of the strongest earthquakes in the eastern United States shook the Mississippi Valley between Arkansas, Tennessee and Missouri. The river ran backward, Reelfoot Lake was born in Tennessee, and the shaking was felt hundreds of miles away. The fault is still active today.
Every fall, monarch butterflies from across the eastern United States and Canada fly up to 3,000 miles to the same mountain forests in central Mexico. None of them has ever been there before. Learn about the long-lived "super generation," how they find their way, and why milkweed matters.
A year is really about 365 and a quarter days, and that extra quarter caused centuries of trouble. Why we add February 29, the little-known rule that skips some leap years, and how in 1582 the calendar simply jumped ahead ten days. In 1752 Britain and the American colonies skipped eleven.
A lightning bolt is about five times hotter than the surface of the sun and strikes the United States about 25 million times a year. How storms build up the charge, how to tell how far away a strike is by counting, the myth about never striking twice, and simple rules that keep you safe outdoors.
We spend about a third of our lives asleep, and the brain is busy the whole time. Learn the 90-minute sleep cycle, what dreams and REM sleep do, how the brain takes out its trash at night, and why staying awake 17 to 19 hours can impair you about like a drink or two.
The Moon pulls the oceans into two high tides a day, always shows us the same face, and is drifting away about an inch and a half every year, measured with mirrors the Apollo astronauts left behind. Fun facts about the twelve men who walked there and how the Moon was probably born.