Why Do Onions Make You Cry? The Science and How to Stop It
Farzan Khan Why do onions make you cry? Learn the chemistry behind onion tears, what new lab research found, and 8 ways to prevent them at home, ranked by evidence.
Farzan Khan
What Happens to the Brain When We Dream? Stages, Science and Myths
What happens to the brain when we dream? Find out which regions switch on, which go quiet, why dreams feel strange, and what science can't yet explain.
Why Do Our Fingers Wrinkle in Water? The Nerve Secret
You stay in the bath or pool a little too long, look down, and your fingertips look like raisins. Most people grow up hearing that skin “soaks up water” and…
Why Do We Yawn When We See Someone Else Yawn? The Science
You’re sitting in class, or in a quiet meeting, and someone across the room opens wide in a long, slow yawn. A few seconds later, you feel it coming too.…
Why Do Clouds Turn Black Before It Rains? Simple Science
The afternoon starts bright. Then, within an hour, puffy white clouds swell into a towering wall that turns gray, then almost black. The wind picks up, and you know what’s…
Why Is the Ocean Blue if Water Is Clear? Simple Science
Fill a glass with seawater and hold it up to the window. It’s clear. Now picture the open ocean from a boat or a plane: deep, rich blue as far…
What is the Difference Between a Meteor vs Meteorite vs Asteroid
A streak of light flashes across the night sky and is gone in a second. Someone shouts “meteor!” Someone else says “asteroid!” And the next day, a neighbor swears a…
Why Do Stars Twinkle but Planets Don’t? Simple Answer
Pick a clear night and find two bright dots, one high in the sky and one a little lower. Watch each for half a minute. One of them may shiver,…
What Is a Z-Score in Statistics? Formula, Examples and How to Read It
A z-score tells you how many standard deviations a value sits from the mean. Learn the formula, compare unlike scores and try our live SAT z-score chart.
What Is a Percentile in Statistics? Meaning, Formula and Real Examples
A percentile tells you what share of values fall at or below a number. Learn the formula, avoid the percentage mix-up and see where US paychecks rank.