Fahrenheit:

The lower defining point, 0 °F, was established as the temperature of a solution of brine made from equal parts of ice and salt.

Celsius:

0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water

Why hasn't anyone used human body normal temperature as 0? It would be much more logical for humans to base temperature scale on our body, not something that is outside.

  • 2
    Please check wikipedia how the Fahrenheit scale was developed. And no, there is no "logic" behind that. Convenience, perhaps. – Karl Mar 31 '17 at 21:01
  • 3
    Interesting point. Water is a pretty important part of human physiology though, so the Celsius scale is not completely irrelevant to the human body. I suspect water's importance to human physiology was a major reason for using it's properties for a temperature scale. I just saw DavePhD's answer though and I had no idea there actually was a "physiological scale"! Again, interesting question. – airhuff Mar 31 '17 at 21:13
  • Why on earth should it make sense to have a temperature scale based on human body temperature, which is not very constant to begin with ? And what does this have to do with chemistry? Please close question. – Karl Mar 31 '17 at 21:27
  • 5
    I will not be voting to close the question as it at least loosely fits the history-of-chemistry tag. Virtually every chemical process has some relationship, cause and/or effect, to temperature. Choice of a temperature scale to be used in the sciences has historically not been a simple process. Different temperature regimes are important to different disciplines. Until relatively recently, erroneous concepts of absolute zero abounded. Although the ultimate choice of temperature scale is fundamentally arbitrary, the history of this choice is loaded with scientific invention and discovery. – airhuff Mar 31 '17 at 23:28
  • As @airhuff, I think this question is valid for "history of chemistry" and hence suggest to keep it. Temperature is one of the fundamental properties of matter; and as science is dynamic, evolving, depending on the field of application some scales are used more frequently, than others. And in contrast to Karl's second comment I assume, it is thanks to both i) establishing a scale (perhaps "at all"), and ii) learning how to measure accurately "temperature" as comparison with references, that we recognized body temperature varies. – Buttonwood Apr 1 '17 at 9:49
up vote 9 down vote accepted

Why nobody used human body normal temperature as 0?

That has been done.

See Medical Thermometry and Human Temperature at page 12:

37° Centigrade scale

29.6° Reaumur

98.6° Fahrenheit

77° Walferdin's tetracentigrade

0° of the physiological scale

Then the physiological scale is further discussed starting on page 265, which includes a drawing of a physiological scale thermometer.

physiological 0 is placed in the centre of the drama, whose acts are health, sickness, and death

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