Under Pressure

The torr is a unit of pressure not included in the International System of Units, based on an absolute scale. In layman's terms, absolute scales have a defined minimum point and measurements increase in a single direction. Conversely, relative scales can start at any chosen point and can move both ways. Celsius and Fahrenheit are relative temperature scales, while the Kelvin scale has an absolute zero (equivalent to -273.15 °C and -459.67 °F), recognized as the lowest conceivable temperature.

Returning to our word of the day, the torr is defined as precisely 1/760 of a standard atmosphere, which translates to 101,325 pascals. Thus, 1 torr is approximately 133.32 pascals. The pascal is the SI unit of pressure.

Historically, one torr equated to one millimeter of mercury. However, definitions of both units were revised in the mid-20th century, leading to a slight discrepancy. This difference is minor—less than 0.000015%—so most people wouldn’t notice it, but precision is key in science. Therefore, it's best not to equate torr directly with millimeters of mercury, lest you ruffle a scientist's feathers.

Interestingly, the torr lacks a designated symbol. Instead, it's written as "Torr" with a capital T, which is also the symbol for tesla—the unit for measuring magnetic fields, not the electric vehicle company established by Elon Musk, who is named after the inventor Nikola Tesla.

The Origin of Torr

The torr is named after Evangelista Torricelli, a 17th-century Italian physicist and mathematician, not to be confused with the 20th-century Canadian model Linda Evangelista. Torricelli, who studied under Galileo Galilei, made significant contributions to the understanding of atmospheric pressure.

Torricelli invented the barometer in 1643, although some evidence suggests that Gasparo Berti, another Italian mathematician, may have developed a water barometer prior. However, Torricelli gained recognition, partly due to his communication methods at the time.

During his time with Galileo, Torricelli challenged the prevailing belief that air was weightless. He theorized that the "sea of air" exerts pressure similar to how water affects submerged objects. His experiments demonstrated that air pressure could be measured, leading to the creation of the barometer.

In a 1966 article for Galaxy Science Fiction, Willy Ley recounted how discussions with Galileo inspired Torricelli to explore air pressure. Galileo had suggested investigating the problem, leading Torricelli to experiment with mercury, which revealed that air pressure could be quantified.

This experiment was groundbreaking, indicating that air has weight and that the atmosphere has a limited height. Torricelli was about 35 years old when he conducted this experiment, but he was soon overshadowed by Blaise Pascal, who demonstrated that mercury levels in the barometer drop at higher altitudes.

The influence of Torricelli extended to later scientists, including Otto von Guericke, who successfully predicted weather changes based on air pressure observations.

Now that you are aware of the torr, the next time you discuss weather with a meteorologist, you might want to ask about their torr readings. Just be prepared for a puzzled look, as the editors of the Spelling Bee have classified "torr" as a dord.

For further reading on another intriguing dord, check out my previous entry here:

The first video titled "Torr Molecule Album Breakdown" explores the intricacies of the torr concept through music.

The second video, "Torr - Molecule (Full Album)," delves into the themes surrounding the idea of torr in a musical context.