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.
