Boyle's air pump

Robert Boyle did not invent the air pump, but he perfected it into a scientific instrument. Building on Otto von Guericke's earlier vacuum devices, Boyle and his assistant Robert Hooke created a pump in 1659 that could evacuate a glass vessel reliably enough for repeated experiments. The pump became a laboratory for investigating what happens when air is removed.

Guericke's Magdeburg hemispheres had demonstrated vacuum dramatically—horses could not pull apart evacuated metal spheres. But his pump was a one-time spectacle, not a research tool. Boyle needed something that could create and release vacuum repeatedly while he observed what happened inside.

The Boyle-Hooke pump used a brass cylinder and piston to extract air through a stopcock from a glass globe called the receiver. The receiver was large enough to contain experimental apparatus: candles, mice, birds, or other test subjects. Through the thick glass walls, Boyle watched what happened as pressure dropped.

The experiments were systematic and revelatory. Candles extinguished. Animals suffocated. Sound could not transmit through vacuum. A feather and a coin fell at the same rate when air resistance vanished. The Aristotelian claim that nature abhors a vacuum fell to empirical demonstration: nature permitted vacuum; it was merely difficult to create.

Boyle formulated his gas law—pressure and volume are inversely proportional at constant temperature—using the pump to compress and expand gases in measured containers. This was the birth of pneumatic chemistry, the quantitative study of gases that would eventually yield oxygen, nitrogen, and the chemical revolution.

The air pump spread through Europe's scientific societies. The Royal Society in London, the Académie des Sciences in Paris, and individual experimenters across the Continent acquired pumps to replicate and extend Boyle's work. The pump became essential laboratory equipment, as fundamental as the microscope or telescope.

What Guericke had built for spectacle, Boyle transformed into a research program. The air pump created a controlled environment where the behavior of matter could be isolated from atmospheric interference.