Human body
You live in it every day, yet there's a lot you may not know about your own body.
31 articles
How many times a day do we blink?
You have almost certainly closed your eyelids at least once while reading this sentence. Have you ever stopped to count how often?
Are you taller in the morning than at night?
The same person can measure a different height in the morning and at night. About 300 years ago, an English clergyman who noticed this is said to have saved several soldiers from being discharged for being too short.
Why do we get hiccups?
That stubborn “hic” you just can’t stop. Everyone gets them, yet what they’re actually for remains surprisingly unclear.
Why are yawns contagious?
See someone yawn, and before you know it, you’re yawning too. How many times will you yawn before you finish reading this?
Why doesn’t the stomach digest itself?
Your stomach turns meat and fish into mush. Yet the stomach itself is an organ made of flesh. How does it keep from dissolving?
Do babies really have more bones than adults?
As we grow, our bodies get bigger but our bone count goes down. Behind that curious subtraction lies a reason that helps babies survive.
Why do we have a dominant hand?
The hand that holds a pen, the hand that throws a ball. Our dominant hand seems settled before we notice—so when, and how, does it take shape?
Do identical twins have the same fingerprints?
If two people share exactly the same genes, surely their fingertips should match too. It’s a tempting thought, but a different drama was playing out in the womb.
How many smells can humans tell apart?
Fresh coffee, earth after rain, bread straight from the oven. Just how many different smells can our noses tell apart?
What is the strongest muscle in the human body?
The biceps? The thighs? Surprisingly, this question doesn’t have one fixed answer.
Do your tears change with your feelings?
Tears of sadness and tears from chopping onions look like the same drops. But are they the same inside? A story of research on tears spanning more than 40 years.
Why does eating ice cream give you a brain freeze?
You gulp down shaved ice, and a sharp pain stabs behind your forehead. The cold is in your mouth, so why does your head hurt?
Why do we get goosebumps?
A cold morning, a piece of music that moves you. What mechanism in the body raises those tiny bumps across your arm?
Is muscle soreness caused by lactic acid?
Two days after your first workout in ages, your legs scream every time you walk down the stairs. But is the usual suspect really the one to blame?
How much does hair grow in a day?
It must be growing every day, yet the mirror never shows a change. So how fast is your hair actually growing?
Why do we dream?
Flying through the sky, meeting someone you’ve missed. What purpose could these strange stories screened while we sleep possibly serve?
How many cells are in the human body?
The number you learned in school and the number in today’s reference books don’t match. In the 21st century, scientists sat down and counted the body’s cells again.
Is blood type linked to personality?
“You’re so organized—you must be type A.” In Japan this is everyday small talk. But when, and from where, did the idea take hold?
Why does time seem to speed up as we get older?
Childhood summers seemed to last forever; an adult year is gone in a blink. Psychologists have been puzzling over this almost universal feeling for more than a century.
Is the tongue “taste map” real?
Sweet at the tip, bitter at the back. Remember that diagram from a textbook? It’s the story of a small misunderstanding that began with a paper more than a century old.
How fast do fingernails grow?
You just trimmed them, and somehow they’re already long again. One doctor spent 35 years recording that tiny change on his own thumb.
Why do we sneeze?
Once your nose starts to tickle, there’s no stopping it. Bright light can set it off, and some claim sneezes are as fast as a bullet train. How much of that is true?
What makes the sound when you crack your knuckles?
Plenty of us were warned that cracking our knuckles would make them swell. Scientists have pursued the source of that satisfying pop with surprising determination.
Why does your stomach growl?
A silent meeting room, and then it happens: that unmistakable rumble. The embarrassing noise turns out to be the sound of a very regular habit your gut keeps.
What percentage of the human body is water?
People often say the human body is mostly water. But how much, exactly? It turns out the share varies surprisingly with age and sex.
Is your earwax type decided by your genes?
Some people’s earwax comes out in dry flakes, while others’ is soft and sticky. Where does that difference come from? Hidden behind it is a trace of humanity’s long journey across the globe.
Would your blood vessels really wrap around the Earth two and a half times?
Lay your blood vessels end to end and they’d circle the Earth two and a half times, or so we’re told. Trace the figure back, and you find an imaginary 140-kilogram man.
Why do we replace our teeth only once?
Sharks go through tens of thousands of teeth in a lifetime, yet we swap ours only once, in childhood. Here’s why, and where research into regrowing teeth stands today.
Why do some people’s faces turn red when they drink?
One glass of beer turns some people bright red; others drink round after round without changing color. The difference lies in a tiny variation in a single gene.
Do we really use only 10 percent of our brains?
Wake up the other 90 percent and you’ll become a genius. It’s a favorite of movies and self-help books, but what do the scientists who study the brain make of it?
Why is human body temperature around 36–37°C?
The idea that “normal” is 37°C was popularized by a German doctor more than 150 years ago. Now it seems that normal itself has been slowly slipping.