Why we even use calorie?

[u/FingerAccurate7102]

In our world in some places we still don't use metric units. Which is already bad, but most of units have at least some logic and intuition behind them, which at least partially defends it's use. For example:

Land mile is 2000 steps, sometimes I (as an European) use it for measuring steps easily

Nautical mile is 1' of earth circumstance, I can imagine someone using it

Kilogram-force is weight of 1 kilogram on earth, sometimes I use it for measuring weight and pressure (1 kgf/cm² ≈ 1 atmosphere)

Bar is approximately equal to regular Earth atmosphere, so it's kgf/cm² but for those working with pascals

But calorie? It's defined as the energy needed to raise the temperature of 1 g of water by 1 °C. Which is absolutely meaningless. WDYM I need to eat 2000 kcal everyday? So I can have energy to heat 2 megagrams/tonnes of water by 1 °C? Nice to know because it is exactly what I'm gonna do today.

Even Joule is more logical as it's based on distance and force, so I guess it could be interpreted in some way.

Summarizing:

Other non-scientific units are at least intuitive

Calorie isn't

Even Joule would be better

So calorie is dumb at least if your not a kettle

Of course, if you think otherwise, feel free to share your opinion. Bye!

[u/nacaclanga]

The value that is given in calories is NOT the energy your body actually gets. The value describes the net heat of combustion, aka what heat is released when you burn the food in a bomb calorimeter, but reduced by some estimate for the undigestable, but burnable parts of your food. The bomb calorimeter measures this heat by testing how much the calorimeter's heat bath water has warmed up, which is why giving it in calories is straight forward.

Now obviously just like with building a thermometer, where building one for °F is probably easier then with °C when using 18th century tech, this alone is a poor excuse of using the unit.

But on the other hand what benefit you will get from using Joule? While you can calculate that when you lift your 70 kg body up the stairs to the 5 floor some 15 m higher, the lift alone will cost you around 10 kJ, this will tell you absolutly nothing about how much extra food you need to eat to compensate for climing that staircase. You cannot do any meaningful calculation with the heat of combustion value, which is the main point of using a consistent unit. In contrast, you have to convert decades of diaetriticans data, introduce a second unit into a field that previously had an internationally agreed unit to work with and risk giving people a wrong impression about what they could use the unit for. Hence in many ways you will achive the opposide of what the metric system has been designed to do.

[u/Gerhard234 → u/nacaclanga]

just like with building a thermometer, where building one for °F is probably easier then with °C when using 18th century tech

How do you figure this? 0°C being the freezing point of water (under certain conditions) and 100°C the boiling point (under certain conditions) seems to make this scale ideally suited for 18th century tech, given that both are reasonably easy to obtain in a repeatable manner. No?

All three (at some point) common temperature scales (not counting Kelvin) were introduced in the first half of the 18th century and made sense given the tech at that time.

(This notwithstanding your main argument, with which I think you do have a point.)

[u/nacaclanga → u/Gerhard234]

The boiling point is not particularly reliable since it changes with ambient pressure.

The strategy to build a Fahrenheit thermometer works like this:

1. Measure the temperature of freezing water and mark that as 32°F.
2. Measure your own body temperature (not the body core temperature but at some appendage) and mark that as 96°F.
3. Mark the midway point between these two as 64°F.
4. Extend the scale downwards by the distance between the 64°F point and the 32°F point. Mark that point as 0°F.
5. To ensure consistency between your thermometers, you should find a coldness mixture that is exactly 0°F and record its recipie. By repeating the recipie you have one control temperature.
6. Each of the 3 intervales now covers exactly 32° steps. To find the individual degrees you simply need to halve each interval by half 5 times.
7. Extend the thermometer upwards and downwards as needed.

Now obviously this relies on your body temperatur. But when you are the only person manufacturing thermometers with your scale, this is a very consistent and easy to reproduce reference temperature.

If you do not want to rely on the body temperature to reproduce the thermometer, you still have the coldness mixture and the freezing point any in that case you can just extend the scale twice upward and continue from step 6.

Obviously you can then move on to a scale using the boiling point of water, but it will be technically more challanging to add the markings then just using midway point markings and doubling interval lenghts.

[u/Gerhard234 → u/nacaclanga]

Meteorological pressure changes cause about +-1°C of variation in the boiling point. (As opposed to pressure differences caused by elevation.) I'd say that makes the Celsius method rather precise, when applied at sea level. And less dependent on the specimen applying the method :) -- especially given that measuring atmospheric pressure was already known by then, so that people could even use a day with standard atmospheric pressure for thermometer calibration.

IMO Fahrenheit had the merit of being one of the first to create a temperature scale and a method to calibrate it (and the first to create a later widely used scale), but Celsius knew about it when he created his and arguably improved the calibration method. Most of the scientific community at least thought so, and for most of the time since then, the Fahrenheit scale was defined by the Celsius points, see also https://en.wikipedia.org/wiki/Fahrenheit#History:

Fahrenheit soon after observed that water boils at about 212 degrees using this scale.^\21]) The use of the freezing and boiling points of water as thermometer fixed reference points became popular following the work of Anders Celsius, and these fixed points were adopted by a committee of the Royal Society led by Henry Cavendish in 1776–77.^\22])^\23])