Why Doesn't the Atmosphere Crush Us?
Hey smart people, Joe here. Horror vacui - “Nature despises a vacuum”. It's a term maybe
you've heard in art, the need to fill all space with detail. But it's an idea that
goes all the way back to the science of Aristotle, the smartest guy alive in the 4th century
BC.
Aristotle believed the universe was full of things, no matter how small you tried to cut
it up, so there could be no place where there wasn't any-thing. The idea of a vacuum,
a space full of nothing, was impossible. Ok then, Mr. Aristotle, how do you explain this?!
OPEN BUMPER
For the next two thousand years, everybody pretty much agreed with Aristotle: vacuums,
voids, and empty spaces couldn't exist. That included the Catholic church, which was
bad news for a guy named Galileo.
In 1634, Galileo had just been brought before the Inquisition for the crime of believing
the Earth wasn't the center of the universe, which was another of Aristotle's bright
ideas. In exchange for keeping his head, he'd promised to retire his telescope, but under
house arrest, he published one final book that basically jump-started physics as we
know it today. Hidden in that book is an experiment that changed the way we look at something
we can't really see: air. Galileo took a glass bottle, and into that
bottle he forced more air. He put it on a scale, opened a valve, letting the compressed
air escape, and the bottle was suddenly lighter. He proved that air weighs something, and if
you took enough away, you'd be left with nothing–a vacuum.
Thing is, everyone was so scared of the church, Galileo had to smuggle his book all the way
to the Netherlands to get it published. But his book eventually made it into the hands
of some curious young scientists, and good thing too, because Galileo had gotten something
very wrong.
One of those young scientists was named Evangelista Torricelli, who was… the owner of some amazing
facial hair. Nice, dude. Torricelli had thought a lot about what drew liquid up in pipes and
straws. What forces the liquid up? Does our mouth
create a vacuum that pulls it up? Galileo believed vacuums and empty spaces
were basically magical, full of a strange power to attract liquids. But Torricelli thought
that idea… really sucked. Thanks to Galileo, Torricelli knew air weighed
something. Maybe it was heavy enough to push liquid around. And this is how he tested that
idea:
He filled a glass tube with mercury, closed at one end, and he submerged the open end
in a pool of mercury. The mercury level in the tube dropped, but it didn't empty all
the way.
Torricelli added a second mercury-filled tube–only this one had a large glass globe on its closed
end. If Galileo was right, and empty space had the power to pull on liquid, the tube
with more empty space should pull its mercury level higher. But the mercury ended up at
exactly the same level in both tubes. No matter how much vacuum was in the tube, the force
holding up the mercury was the same. Vacuums don't suck. Air pushes!
A bubble of air as big as the tip of my little finger contains more than a billion billion
molecules, and every one of them is zipping around and colliding with others a billion
times a second.
This atomic pinball is why the air in a tire can hold up an entire car, and it's why air doesn't just push down, it pushes in every direction.
When we expand our mouths to drink from a straw, the atmosphere pushes the liquid up
into our mouth! When we expand our diaphragms to breathe, we aren't sucking air in, the
atmosphere is falling into our lungs! When you turn on the vacuum cleaner, you aren't
sucking anything, the atmosphere is pushing dirt out of your house. I mean, once you know
this, you really can never look at the world the same way again. Whoa.
Torricelli never published his results about vacuums and air pressure, because he was afraid
of that whole Inquisition thing. But he did write it in a letter to a friend, who told
a few more friends, and thanks to that secret science underground, a few curious folks across
Europe began to ask just how strong the invisible stuff around us really is…
In 1657, the mayor of Magdeburg, Germany, Otto von Guericke, had figured out how pump
air out of two tight-fitting half-domes, forming a sealed globe with a vacuum inside. The weight
of air is so powerful, it allegedly took 32 horses to rip the hemispheres apart!
Not only does air weigh something… it weighs a very great deal indeed. Enough to overpower
even someone as buff as me :) Ready?
Ready!
The mass of all the air in this room is approximately 500 kg. What's crazy is it's pushing on
me with enough force, that even though the vacuum hose only lowers the pressure inside
the bag by about 10%, I'm basically immobilized.
This seems to defy common sense, because air just doesn't seem that heavy. I mean, if
we live at the bottom of an ocean of air, how can we move through it without even noticing
it? If air is pressing on us that hard all the time, why don't our bodies get crushed?
Because as hard as the atmosphere pushes down on us, we're pushing right back! Our bones,
our skin are all incredibly strong! Any open spaces like our lungs are being pushed out
by air so they don't collapse. And our cells are filled with liquid which has its own pressure
pushing back on the atmosphere!In fact, without this ocean of air, we'd look as ugly as
the deep-sea blobfish looks outside of its ocean. They're surprisingly handsome in
their native pressure.
So next time life gets you down, if it ever just feels like too much, just take a second
to remember about how much pressure you've put up with every day of your life without
even realizing it. You're stronger than you think.
Stay curious.
