Anders Celsius: The Man Who Measured Temperature Backwards

The Astronomer Who Changed How We Measure Heat

When you check the weather forecast and see that it’s 25°C outside, you’re using a temperature scale named after Anders Celsius—a Swedish astronomer who never actually used the scale as we know it today.

Who Was Anders Celsius?

Anders Celsius (1701-1744) was born in Uppsala, Sweden, into a family of scientists. His grandfather was a mathematician, and his father was an astronomy professor. Anders followed in their footsteps, becoming a professor of astronomy at Uppsala University at just 29 years old.

Celsius was a man of many achievements:

He was the first to measure the brightness of stars systematically
He participated in an expedition to Lapland to measure the shape of the Earth
He founded the Uppsala Astronomical Observatory

But his most lasting legacy came from a paper he published in 1742.

The Original Celsius Scale

Here’s where history gets interesting. In Celsius’s original scale:

0° was the boiling point of water
100° was the freezing point of water

Yes, you read that correctly. The scale was inverted from what we use today!

Why did Celsius do this? The most likely explanation is practical: he wanted to avoid negative numbers in everyday weather measurements. In Sweden, temperatures below freezing are common. With his inverted scale, Swedish weather would almost always show positive numbers.

The Great Flip

After Celsius’s death in 1744 (from tuberculosis, at just 42 years old), his colleague Carl Linnaeus—the famous botanist—is often credited with inverting the scale. However, historical evidence suggests it was actually Jean-Pierre Christin, a French scientist, who independently proposed the inverted scale the same year as Celsius’s original proposal.

The Swedish instrument maker Daniel Ekström created thermometers with the inverted scale, and it gradually became the standard.

Celsius vs. Centigrade

For many years, the scale was actually called “centigrade” (meaning “hundred steps”). It wasn’t officially renamed “Celsius” until 1948, when the General Conference on Weights and Measures adopted the name to avoid confusion with the centesimal grade used in angle measurement.

How Celsius Compares to Other Scales

Fahrenheit (1724)

Daniel Gabriel Fahrenheit, a German physicist working in the Dutch Republic, developed his scale about 18 years before Celsius. He used:

0°F: The temperature of a salt-ice-water mixture
32°F: Freezing point of water
96°F: Approximately human body temperature

Kelvin (1848)

William Thomson (later Lord Kelvin) proposed an absolute temperature scale where 0 represents absolute zero—the theoretical temperature at which all molecular motion stops.

0 K = -273.15°C
Water freezes at 273.15 K
Water boils at 373.15 K

Why Celsius Won (Mostly)

The Celsius scale became dominant for several reasons:

Decimal-friendly: The 100-degree span between freezing and boiling aligns with the metric system’s base-10 logic
Intuitive reference points: Water’s phase transitions are universally relevant
Scientific adoption: Most scientific work uses metric units, and Celsius fits naturally

Today, Celsius is the standard in almost every country—except the United States, which still primarily uses Fahrenheit for everyday purposes (though American scientists use Celsius).

A Personal Legacy

Anders Celsius died young, but his name lives on every time someone checks the temperature. It’s a fitting tribute to a scientist who dedicated his life to precise measurement—even if we did have to flip his scale around.

Conversion Tip: To convert Celsius to Fahrenheit, multiply by 9/5 and add 32. Or just use Converter Fun!