Deaths on April 25

Anders Celsius, Swedish astronomer, physicist, and mathematician (b. 1701)

Anders Celsius (Swedish pronunciation: [ˈânːdɛʂ ˈsɛ̌lːsɪɵs]), a towering figure in 18th-century Swedish science, was born on November 27, 1701, and passed away on April 25, 1744. He distinguished himself as a brilliant astronomer, physicist, and mathematician, whose contributions, particularly in the realm of temperature measurement, profoundly impacted the scientific world and continue to shape our daily lives.

An Esteemed Academic and European Explorer

A native of Uppsala, Sweden, a prominent center of learning, Celsius was appointed Professor of Astronomy at Uppsala University in 1730, a prestigious position he held until his death. His formative years as an academic were significantly enriched by an extensive scientific expedition across Europe, spanning from 1732 to 1735. During this insightful "Grand Tour," Celsius meticulously visited and engaged with numerous notable observatories and leading scientific minds in Germany, Italy, and France. These travels were far more than mere sightseeing; they were pivotal opportunities for him to absorb the latest astronomical and physical research, exchange ideas with contemporaries, and broaden his scientific perspective, all of which laid crucial groundwork for his later innovations back home.

Pioneering the Uppsala Astronomical Observatory

Upon his return to Sweden, Celsius spearheaded the establishment of a cutting-edge astronomical observatory in Uppsala, realizing his vision in 1741. This institution, the Uppsala Astronomical Observatory, quickly became a vital hub for scientific research and education within Sweden. Equipped with the most advanced instruments of the era, it fostered a new generation of scientists and significantly advanced the study of the cosmos. Celsius proudly served as its first director, guiding its initial development and shaping its research agenda.

The Enduring Legacy: The Celsius Temperature Scale

Without doubt, Celsius's most globally renowned contribution is the temperature scale he proposed in 1742. Interestingly, his original "Centigrade" scale had a unique configuration: he designated 0 degrees as the boiling point of water and 100 degrees as its freezing point, under standard atmospheric pressure. While this may seem counter-intuitive today, it offered a logical consistency for some scientific applications of his time. However, this arrangement was short-lived. Shortly after Celsius's death, likely around 1745, and notably influenced by his contemporary Carolus Linnaeus, the scale was wisely inverted to its now-familiar form: 0 degrees for the freezing point of water and 100 degrees for its boiling point. This more intuitive progression, where higher numbers signify greater heat, rapidly gained acceptance. Though initially known as the Centigrade scale (from Latin 'centum' for one hundred and 'gradus' for steps), it was officially renamed the Celsius scale in 1948 by the Ninth General Conference on Weights and Measures, a fitting tribute to its brilliant originator. Today, the Celsius scale is the standard unit of temperature measurement across nearly every nation worldwide, indispensable in scientific research, meteorology, and daily life.

Beyond the Thermometer: A Multidisciplinary Scientist

While the temperature scale is his most celebrated achievement, Anders Celsius’s scientific curiosity and contributions spanned far wider. He was an active participant in significant geodetic measurements, notably joining the renowned French expedition to Lapland (1736-1737) led by Pierre Louis Maupertuis. This expedition was crucial for measuring the length of a degree of longitude near the Arctic Circle, providing vital empirical evidence that the Earth is indeed flattened at the poles, just as Isaac Newton had theoretically predicted. Furthermore, Celsius dedicated considerable time to observing and recording the aurora borealis, meticulously studying its characteristics. He also compiled a catalog of 316 stars, demonstrating his profound commitment to observational astronomy and adding to the collective knowledge of the celestial sphere.

FAQs About Anders Celsius and His Contributions

Who was Anders Celsius?

Anders Celsius (pronounced [ˈânːdɛʂ ˈsɛ̌lːsɪɵs]) was a highly influential Swedish astronomer, physicist, and mathematician from the 18th century, primarily remembered for developing the Centigrade, now Celsius, temperature scale.

What is Anders Celsius most famous for?

He is most famous for inventing the Centigrade temperature scale in 1742. This scale, later reversed to its modern form (0°C for freezing, 100°C for boiling) and officially renamed Celsius in his honor, is used globally.

Why was the original Celsius scale "inverted"?

Celsius’s initial design set the boiling point of water at 0 degrees and the freezing point at 100 degrees. While the exact reasoning is not definitively known, it might have related to older thermometer conventions where mercury expanded and moved down the tube upon heating. This configuration was later reversed to the modern 0-100 scale, most likely by Carolus Linnaeus or a colleague, shortly after Celsius's death.

When was the Centigrade scale renamed Celsius?

The Centigrade scale was officially renamed the Celsius scale in 1948 by the Ninth General Conference on Weights and Measures to formally recognize Anders Celsius's pioneering work.

Is Centigrade the same as Celsius?

Yes, for practical purposes, Centigrade and Celsius refer to the same temperature scale. "Centigrade" describes the scale's 100 divisions between the freezing and boiling points of water. "Celsius" is the official and preferred name, honoring its inventor, Anders Celsius.