After surviving the worst massacre of the Thirty Years’ War, Otto von Guericke made several historic scientific discoveries. Self-funded, he invented the vacuum pump, pioneered the concept of the absolute vacuum of space, measured the weight of air and used air pressure to make weather forecasts.
His vacuum pump famously created such an impressive vacuum between two metal hemispheres that 16 horses could not pull them apart, while his electrical experiments led him to conclude incorrectly that what we call gravity is an electrical force. He believed our planet weighs less than a feather!
Otto von Guericke was born into an affluent family on November 30, 1602 in the German city of Magdeburg. His birth name was Otto Gericke. He changed his name in 1666 when he was ennobled by Emperor Leopold I.
Otto’s father was Hans Gericke, Magdeburg’s treasurer, who would later become its Mayor. His mother, Anna von Zweydorff, came from a wealthy, aristocratic family. Otto’s parents were members of the Lutheran Church. He was their only child.
For the first 15 years of his life, Otto von Guericke was educated by private tutors. His maternal grandfather gave him money to get a college education and at age 15 Guericke left home.
- He spent the years 1617-1619 at the University of Leipzig studying philosophy and law.
- The Thirty Years War began in Leipzig in 1618, when Protestant protestors threw Catholic bishops from castle windows 68 feet above the ground. The bishops survived, but millions would die in the resulting Catholic vs Protestant war. Guericke, at his parents’ urging, left Leipzig in 1619.
- In the years 1619 and 1620 Guericke studied metaphysics at the Academia Julia in Helmstedt. His father died in 1620 and Guericke returned home for a few weeks.
- From 1621-1623 Guericke studied law at the University of Jena.
- In the years 1623 and 1624 Guericke studied mathematics, physics, fortification engineering, Dutch, English and French at the University of Leiden in Holland.
- In the years 1624 and 1625 Guericke toured France and England refining his language skills
Work, War and Massacre
In 1626, age 24, he was elected to Magdeburg’s town council and got married. Life was good.
Five years later, in 1631, his life and Magdeburg were devastated when the forces of the Holy Roman Empire and Catholic League attacked the Protestant city. Amid countless atrocities, 20,000 of Magdeburg’s citizens died – many in fires that raged through the city. Only 5,000 survived.
Guericke gave all his money and possessions to marauding solders and was spared. One of his young sons, however, was wounded and later died. The entire Guericke family was held captive until a nobleman paid a ransom for their release.
Guericke and his wife were left penniless but alive. He later gave an eyewitness account of the sacking.
A year after the massacre the census of 1632 recorded only 449 people living in the city. In the same year, Guericke returned to Magdeburg’s ruins and ashes, where he used his engineering skills to help rebuild his city.
He started a brewery, and in 1646, age 44, was elected to serve as one of the new city’s four mayors – each mayor served six months in rotation. Guericke retired from this role in 1678, age 76.
Guericke’s Lifetime in Context
Otto von Guericke’s Contributions to Science
The Vacuum Pump
Guericke saw his hometown consumed by fire in 1631. In the 1640s, he began trialing water pumps for firefighting.
In about 1647, Guericke began modifying water pumps. He discovered that he could use a pump to remove air from a sealed metal or glass jar. He had produced the world’s first vacuum pump.
Measuring the Weight of Air
In 1654, Guericke demonstrated his vacuum pumps to Emperor Ferdinand III, who was thoroughly impressed.
The emperor asked Guericke to repeat his demonstrations for university professors, who were likewise impressed. Guericke showed them how his pumps allowed him to find the weight of air in a vessel. More dramatically, he used the sudden evacuation of a glass vessel to cause an implosion that shattered the glass into a thousand pieces.
By 1654, Evangelista Torricelli and Blaise Pascal had already established that air has weight. Guericke’s work was carried out independently of his brilliant contemporaries. His vacuum pumps and his demonstrations of the properties of vacuums were firsts.
Air Pushes on Everything with a Powerful Force
In 1657, Guericke performed his most famous experiment. His technicians machined two 20-inch diameter copper hemispheres, one with a valve through which air could be pumped out, shown below.
The Vacuum of Space
In his great work Experimenta nova, Guericke noted that the stars were known to lie at enormous distances from our planet – distances so huge, they were bewildering. This was known because no star showed any parallax relative to Earth’s radius.
What, he asked, lies within the enormous distances separating us from stars?
As we’ll see, Guericke believed, with good reason, that space is a vacuum.
He explained that in his “horses and hemispheres” experiment, the horses could not pull the hemispheres apart because the weight of the whole sky was pushing them together. This meant that the sky had a finite weight, therefore a finite amount of air surrounded the planet. He explained how this finite weight could be calculated.
He reasoned that if you rise high enough above Earth, you must leave this finite weight behind. Air pressure must fall to zero. He concluded that the planets and stars are separated by airless space – a vacuum.
Guericke noticed that the height of mercury in a barometer – the device was invented by Evangelista Torricelli in 1643 – changed from day to day. This meant that air pressure was not constant.
Guericke recorded air pressures for some time. He noticed that when the pressure was rising, the weather would tend to be fine. When it was falling, the weather often worsened. He used these observations to make weather forecasts. Today, air pressure is still an important factor in the computer models used to make weather forecasts.
The Electrostatic Globe
Guericke took a hollow glass sphere, poured sulfur powder into it, and heated the sphere to melt the sulfur.
After it cooled, he smashed the glass to release the resulting solid sulfur ball, setting it on a rod as shown below.
He stored the ball in ‘a dry place of low humidity.’ (William Gilbert wrote in De Magnete in 1600 that in humid conditions the power of static electricity to attract objects decreases.)
Guericke found that after rubbing the ball with his hand, it would pick up small bits of leaves and paper from a wooden tray about 10 cm below. When he rotated the sphere these pieces remained clinging to its surface. He wrongly concluded that what we today call static electricity explained why people and animals, etc, are stuck to the rotating Earth’s surface.
The Earth has No Mass
In 1686, Isaac Newton published Principia Mathematica Philosophiae Naturalis. One of his world-changing ideas was his second law, which we write today as F = ma. The letters stand for force, mass, and acceleration.
When Guericke published Experimenta nova in 1672, he did so before Newton’s ideas were known. In fact, in addition to being the year of Newton’s Principia, 1686 was the year of Guericke’s death.
By 1672, scientists such as Marin Mersenne and Scipione Chiaramonti had made reasonable estimates (correct to within an order of magnitude) of the Earth’s weight. (No difference was recognized between weight and mass in those times). Guericke, however, dismissed their work. He insisted that Earth’s weight was zero.
In fairness to Guericke we can say with the benefit of hindsight that although he makes some mistakes, not everything he says is wrong. He says that Earth has a particular property that makes everyday objects feel heavy – he’s right. He says that if Earth were to disappear then objects would no longer be heavy – he’s right again. However, Earth’s property that makes objects around it feel heavy is its huge mass, which Guericke says is zero. He is convinced that it is the electrical property he observed with his sulfur ball that makes things on Earth feel heavy.
Moreover, Guericke clings to the fiction that heavier objects fall faster than lighter ones, ignoring the fact that decades earlier Galileo had established this to be untrue. In keeping with Aristotle’s ancient ideas, Guericke believes the behavior of objects is determined by their ‘natural places.’
Guericke’s perspective is an interesting illustration of the clash between the emerging new physics of the 1600s and the highly flawed, but still highly influential, ancient physics of Aristotle.
Some Personal Details and the End
In September 1626, age 24, Guericke married Margaretha Alemann, the daughter of a Magdeburg councilor. The couple had three children: Anna Catharina, Hans Otto, and Jakob Christoph. Only Hans Otto survived infancy.
In 1645, after 19 years of marriage, Guericke’s wife Margaretha died. In 1652, he married Dorotha Lentke, daughter of Magdeburg’s mayor. The couple had no children.
In June 1681, there was an outbreak of bubonic plague in Magdeburg. Guericke, age 79, and Dorotha fled from the city to his son Hans Otto’s house in Hamburg.
Otto von Guericke died peacefully in his bed at age 83 in Hamburg on May 21, 1686. He was survived by Dorotha, Hans Otto, and Hans Otto’s children.
Guericke’s body was returned to Magdeburg where it was placed in the family’s crypt in the Johanniskirche.
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