Measurement inventions that made accuracy possible

The ancient Egyptians built massive stone structures called obelisks, which had a dual purpose: to pay homage to gods and kings and to keep track of time throughout the day. Obelisks were meticulously carved to a specific height and placed with a purpose. As the sun rose and set, its rays would cast a shadow that moved across the ground throughout the day. The markers strategically placed around the base of the obelisk tracked the sun’s movement to tell the time. Obelisks may have been the first recorded attempt to keep track of time throughout the day.  

A later development was the sundial. This ancient device was used to divide a day into 12 parts, including two “twilight hours” at dawn and dusk. It had a long stem with five variably spaced marks that could be oriented east-west in the morning. When the elevated crossbar on the east end cast a shadow over the marks, the device could measure the morning hours. At noon, the device was turned in the opposite direction to measure the afternoon hours. 

Faced with the challenge of building colossal structures like the pyramids, the ancient Egyptians needed a way to ensure everything was perfectly level. Their ingenious solution was to create this simple tool, which predates even bubble levels and consists of a wooden A-frame with a string hanging from the center. If the surface were perfectly flat, the string would hang straight down, centered between the two legs of the “A.” The weight would pull the string towards the lower side if the surface weren’t level. Markings on the A-frame indicated how far off level a surface was based on the movement of the weight. 

In the 1640s, Evangelista Torricelli,  an Italian physicist, mathematician, and a student of Galileo Galilei invented the barometer to measure atmospheric pressure. Torricelli assumed the air exerted a force on the water equal to its weight. He designed an experiment to see if air pressure played a role. He filled a tube with mercury, sealed one end, and dipped it into a basin of mercury. As some mercury fell within the tube, Torricelli realized two things. First, the weight of the air pushing down on the basin must be holding up the remaining mercury in the tube. Second, the space above the mercury in the tube had to be empty, a vacuum.  

Through his now-famous experiment with mercury, Torricelli not only demonstrated the existence of a vacuum and the influence of air pressure, but also paved the way for a new era in meteorology. His breakthrough transformed our understanding of weather, and the barometer, a direct result of his experiment, remains a vital tool for meteorologists to this day, enabling them to predict and understand weather patterns. 

The everyday protractor used to measure angles has a rich history that predates standardized measurement systems. While the modern design we recognize today dates from the 19th century, an instrument resembling a protractor was found in the tomb of Kha, an ancient Egyptian architect, dating back to 1400 BC. 

Although the exact invention date remains unclear, the first documented protractors appeared 500 years ago. They were designed specifically for measuring and drawing angles. By the 17th century, protractors were essential tools for navigators at sea and surveyors on land. These early versions were like the classic semicircular design.  

The 18th century saw the development of more complex protractors, such as the three-arm protractor with a rotating scale for precise angle measurement. Finally, in the 20th century, the protractor became a familiar sight in classrooms consolidating its place as a fundamental tool for mathematics.