Measuring heat and the invention of the thermometer
Before we had scales, heat was just a feeling. Learn how early inventors moved from 'fire pyramids' to the precise temperature sensors we use today.
Best quote from Measuring heat and the invention of the thermometer
We went from observing the effect of heat (temperature) to measuring the quantity of energy. It’s like the difference between knowing the speed of a car and knowing how much gas is in the tank.
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Theory of heat and temperature measurement early discovery
Frequently Asked Questions
Early thermoscopes, like those used by Galileo and his predecessors, were open-system devices where a tube of water was exposed to the outside air. Because the tube was not sealed, the water level reacted to both temperature changes and changes in atmospheric pressure. This meant the device functioned as a thermometer and a barometer simultaneously, making it impossible to get an accurate temperature reading during weather shifts.
The Fahrenheit scale, developed by Daniel Gabriel Fahrenheit in 1714, was based on a 180-degree spread between the freezing point (32°) and boiling point (212°) of water, using mercury for high precision. The Celsius scale, proposed by Anders Celsius in 1742, utilized a decimal-based "centigrade" system with exactly 100 degrees between freezing and boiling. While Fahrenheit focused on mathematical harmony and reliable manufacturing, Celsius sought a simpler, universal standard based strictly on the properties of water.
Latent heat, a concept discovered by Joseph Black, refers to "hidden" heat that is absorbed or released by a substance during a change of state (such as ice melting into water) without changing its temperature. While temperature measures the intensity of heat or molecular motion, latent heat explains why a pot of ice water stays at exactly 32 degrees Fahrenheit even as heat is added, as that energy is being used to break molecular bonds rather than raise the temperature.
Modern thermometers rely on electrical and radiation-based sensors rather than expanding liquids. Digital thermometers often use the "Seebeck Effect," where joining two different metals and heating them creates a tiny, measurable electric current. Contactless infrared thermometers, or pyrometers, measure the infrared radiation (invisible light) that every object emits; the device calculates the temperature based on the intensity of the "glow" coming from the object.
The Caloric theory proposed that heat was an invisible, weightless fluid that flowed from hot objects to cold ones. This theory was eventually debunked by Count Rumford’s observations of cannon-boring, where he noticed that friction generated an endless supply of heat. If heat were a fluid stored within the metal, it would eventually run out; because it didn't, scientists realized heat was actually a form of motion (kinetic energy) rather than a physical substance.
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From Columbia University alumni built in San Francisco
"Instead of endless scrolling, I just hit play on BeFreed. It saves me so much time."
"I never knew where to start with nonfiction—BeFreed’s book lists turned into podcasts gave me a clear path."
"Perfect balance between learning and entertainment. Finished ‘Thinking, Fast and Slow’ on my commute this week."
"Crazy how much I learned while walking the dog. BeFreed = small habits → big gains."
"Reading used to feel like a chore. Now it’s just part of my lifestyle."
"Feels effortless compared to reading. I’ve finished 6 books this month already."
"BeFreed turned my guilty doomscrolling into something that feels productive and inspiring."
"BeFreed turned my commute into learning time. 20-min podcasts are perfect for finishing books I never had time for."
"BeFreed replaced my podcast queue. Imagine Spotify for books — that’s it. 🙌"
"It is great for me to learn something from the book without reading it."
"The themed book list podcasts help me connect ideas across authors—like a guided audio journey."
"Makes me feel smarter every time before going to work"
"Instead of endless scrolling, I just hit play on BeFreed. It saves me so much time."
"I never knew where to start with nonfiction—BeFreed’s book lists turned into podcasts gave me a clear path."
"Perfect balance between learning and entertainment. Finished ‘Thinking, Fast and Slow’ on my commute this week."
"Crazy how much I learned while walking the dog. BeFreed = small habits → big gains."
"Reading used to feel like a chore. Now it’s just part of my lifestyle."
"Feels effortless compared to reading. I’ve finished 6 books this month already."
"BeFreed turned my guilty doomscrolling into something that feels productive and inspiring."
"BeFreed turned my commute into learning time. 20-min podcasts are perfect for finishing books I never had time for."
"BeFreed replaced my podcast queue. Imagine Spotify for books — that’s it. 🙌"
"It is great for me to learn something from the book without reading it."
"The themed book list podcasts help me connect ideas across authors—like a guided audio journey."
"Makes me feel smarter every time before going to work"
"Instead of endless scrolling, I just hit play on BeFreed. It saves me so much time."
"I never knew where to start with nonfiction—BeFreed’s book lists turned into podcasts gave me a clear path."
"Perfect balance between learning and entertainment. Finished ‘Thinking, Fast and Slow’ on my commute this week."
"Crazy how much I learned while walking the dog. BeFreed = small habits → big gains."
"Reading used to feel like a chore. Now it’s just part of my lifestyle."
"Feels effortless compared to reading. I’ve finished 6 books this month already."
"BeFreed turned my guilty doomscrolling into something that feels productive and inspiring."
"BeFreed turned my commute into learning time. 20-min podcasts are perfect for finishing books I never had time for."
"BeFreed replaced my podcast queue. Imagine Spotify for books — that’s it. 🙌"
"It is great for me to learn something from the book without reading it."
"The themed book list podcasts help me connect ideas across authors—like a guided audio journey."
"Makes me feel smarter every time before going to work"
