How the Inquisition led to the Vacuum Pump

How in the world would the inquisition lead to the invention of the vacuum pump?  And what does that have to do with electricity?  I’ll tell you and along the way.

I will also talk about heavy air, an impatient Duke, a panicked Galileo, unfortunate facial hair, air superglue, an impressive demonstration with 24 horses, and a really fantastically dumb Physics demonstration involving a stinky ball on a stick.

Table of Contents

Who is Galileo and what did he discover?

How Evangelista Torricelli Invented The Barometer

The First Vacuum Pump

Who is Galileo and what did he discover?

This story begins in 1633 when a 70-year-old Galileo is in serious trouble.  The religious leaders in Rome were very upset with him for implying that Earth circled the sun and thus was not the center of the universe

In fact, he had to prostrate himself in front of the, “inquisitors general,” to denounce the, “heresy of having held that the sun is the center of the world.” Unable to study the stars, he decided to put together all of his “non-planetary” Physics from the previous 30 years and publish it as a book.  The Inquisition leaders didn’t know it, but this would be even more revolutionary and, well, heretical.    

Galileo did experiments on the motion that was the foundation of Newton’s laws (think Tower of Pisa).  While studying how objects moved, he started to think about air resistance.  That caused him to wonder, what is air?  How much does it weigh or does it have any weight at all?  Galileo decided to solve this problem directly: by weighing the air on a balance scale. 

First, he took a bottle with a straw and a valve in it and weighed it on a scale.  He pumped in extra air and the bottle weighed a few grams of sand more.  When he released the air it weighed a few grams of sand less.  So, air weighs something, but what compared to water?  Galileo then took the bottle and filled it ¾ full of water (without letting any air escape, so that the air got smushed). 

He then carefully weighed the bottle and then let the air escape and weighed the bottle again, so he knew the weight of the air that escaped.  He assumed that the volume of air that left the bottle was the same as the water that displaced it.  In this manner, with just a bottle, water, a scale, and sand he determined that air is almost 400 times lighter than water. 

Now, this sounds like nearly nothing, and it is for the air in a bottle. 

However, think about the weight of air in a big building, say the Pantheon in Rome.  Imagine you took all of the air from inside and measured it on a scale.  How much would just the air weigh?  1 pound? 10 pounds? 100 pounds?  Just the air in that building weighs over ready 150,000 pounds!! Which is crazy. 

This caused Galileo to panic he decided that air weighs something in a bottle but once released it is weightless!  He said, “air in air loses all its weight.”

This was a mistake and a doozy. See, in 1630, the Grand Duke of Florence was trying to get water pumped uphill. Even the best pumps conked out at around 33 feet and no one really knew why. Galileo didn’t realize that he had the solution– and it all has to do with his heavy air.

How Evangelista Torricelli Invented The Barometer

Three months before he died, Galileo hired a brilliant assistant with a stupidly oversized mustache and goatee and the lyrical name of Evangelista Torricelli. Torricelli ignored Galileo’s freak-out about the weightless air.  He thought that air always had weight and it was pressing on us at all times. 

In fact, according to Torricelli, “We live submerged at the bottom of an ocean of air.”   The air pushes on us a lot but in every direction so we don’t notice it!  Torricelli decided that the reason that suction pumps work is not that vacuums suck but because the atmosphere pushes on us and the vacuum doesn’t push back. 

In 1644, Torricelli came up with an experiment with mercury to demonstrate air pressure.  He used mercury because it is much denser than water so if a pump could lift 33 ft of water it could only lift 2.5 feet of mercury – a much more manageable size. 

Torricelli then took a 3-foot-long tube, filled it with mercury, covered the end, and upended it in a container of mercury.  He then removed the cover and ½ a foot of mercury fell out of the tube leaving a gap at the top full of… nothing (as no air could get in). 

Torricelli had made a vacuum without suction, and he made a device of magical properties with a column of mercury suspended against gravity.  The air is pressing on the mercury in the cup, but nothing is pushing back in the top of the tube, so the AIR is what is holding the mercury in place.  Torricelli proved the rule, “Vacuums don’t suck; the air pushes.” 

In fact, air pressure can change, if, for example, if you change altitude or a storm is about to start.  When the outside air pressure changes, the height of the column of mercury changes too! That is why air pressure is often measured in mmHg (millimeters of Mercury) or Torr (short for our fellah Torricelli)) and the device Torricelli invented is called a “the barometer” (or pressure meter).   

The First Vacuum Pump

And now we get to a German politician named Otto Von Guericke.  When Guericke heard about Torricelli’s device he was entranced. Guericke was actually the first person to think of using Torricelli’s barometer to predict storms making him the father of meteorology.  But Guericke was particularly interested in the vacuum at the top of the barometer.   

He wondered if instead of having gravity remove a bit of liquid and create a vacuum if he could use a water pump to remove water and create a vacuum.  So, sometime in the late 1640s, Guericke filled a wooden casket with water, closed and sealed it, and then removed the water with a pump he borrowed from the fire brigade.  

Unfortunately, the air just seeped in through the wood.  He then tried it again on a metal container and the container promptly imploded!  Finally, he created two 20-inch diameter extra-thick copper hemispheres that he fit together in a sphere, and it worked!

Still, he was frustrated because no matter how hard he tried he couldn’t remove all of the water.  In 1650, he had a thought: did he even need water at all?  Could his pump be modified to pump out air instead of water?  Guericke created a device that was basically a piston in a cylinder with two valves. 

When he pulled on the piston the air would expand into the cylinder and when he pushed on the piston the air would flow out of the cylinder into the atmosphere.  This was the first vacuum pump!  Now when he used his pump these spheres stuck together like superglue but as soon as air was let in they would fall apart!  What is going on here

Just like Torricelli, Guericke was demonstrating the power of the air.  When he removed the air from inside the sphere, the atmosphere pushed on the outside but nothing pushed back on the inside.  Therefore, in order to split the two hemispheres, you had to add as much force as air has.  This is a surprisingly large force.  

Guericke began doing impressive demonstrations with strong men playing tug of war on the sphere.  He even upped the wow factor with two teams of horses dramatically pulling on the hemispheres.

You might wonder what this has to do with electricity.  Well, that’s coming.  See, the thing is, despite the fact that the vacuum pump ended up being a practical device and vital to the development of the combustion engine Guericke wasn’t interested in practicality. 

He was interested in philosophy.  His curiosity with vacuums had to do with his belief, like Galileo before him, that the Earth moves around the Sun.  Guericke also believed (as we do today) that space was filled with nothing, or a vacuum.  He was making a vacuum so that he could prove that they could exist. 

Therefore, Guericke had experiments and theories for the nature of space, and ones for the air in our atmosphere.  What he needed was an experiment to model the Earth, and for that reason, he came up with a truly strange idea, he modeled Earth with a ball of smelly sulpher on a stick and modeled gravity with static electricity. 

Guericke never said why he used sulpher, it smells like rotten eggs and is difficult to work with.  The only thing I can think of is that volcanoes can sometimes smell sulphuric so maybe he felt it was a clue to the nature of Earth. Anyway, He rubbed his “Earth” and picked up pieces of leaves and feathers with static electricity. 

Guericke felt like this modeled how all the people and plants on Earth stay on the surface.  By the way, this is a ridiculous theory and has no relationship to how gravity actually works.

However, for all his smelly play-acting, Guericke realized something new.  Guericke detected that after a while, the small objects fell off the sphere.  Moreover, they didn’t just fall off, they repel off the sphere.  In other words electrics can repel as well as attract. 

Guericke’s book was very popular and inspired the study of vacuums in Europe.  His studies with his “wonderful globe” were mostly ignored, however, probably due to their sheer ridiculousness not to mention their lovely odor.

Still, because of Guericke, almost all scientists knew that electricity could repel.  It was actually Guericke’s work on vacuums that inspired the next breakthrough in electricity. 

A shaken barometer steered Isaac Newton’s poor, abused assistant towards the creation of the first fluorescent lamp way back in 1705, almost 100 years before the invention of the battery and well over 200 years before the first commercial fluorescent light bulb. 

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