Why does Celsius temperature in degrees have +/- signs, since it's scalar?

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Discussion Overview

The discussion revolves around the nature of temperature scales, specifically the Celsius scale, and the implications of using positive and negative signs in temperature readings. Participants explore the definitions and characteristics of scalar quantities, the significance of zero points in temperature scales, and the relationship between different temperature scales such as Celsius, Fahrenheit, and Kelvin.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants question why Celsius temperatures can have +/- signs, asserting that scalars can be negative and that temperature is not merely a magnitude.
  • Others suggest that the Celsius and Fahrenheit scales relate to arbitrary points on an absolute scale, with the Kelvin scale being more intuitive due to its non-negative values.
  • A participant notes that the Celsius scale was designed with 0°C as the freezing point and 100°C as the boiling point of water, which is a common reference in everyday life.
  • There is a discussion about the historical context of the Celsius scale, including a claim that it was originally defined in reverse before being changed by Linnaeus.
  • Some participants argue that while the Celsius scale has logical reasons for its definitions, it is still arbitrary in a broader context, as different values could have been chosen for similar reasons.
  • Another participant counters that if the Celsius scale is considered arbitrary, then the Kelvin scale could also be viewed in the same light, as both are based on the same physical phenomena.
  • There is a debate over the definition of "arbitrary," with some participants suggesting that the term may not apply in the context of temperature scales due to their logical foundations.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of temperature scales, the concept of arbitrariness, and the implications of using positive and negative signs in temperature readings. The discussion remains unresolved, with differing opinions on the definitions and significance of the Celsius scale.

Contextual Notes

Participants reference the historical development of the Celsius scale and its relationship to other temperature scales, but there are unresolved questions about the implications of these definitions and the nature of scalar quantities.

ELLE_AW
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Why does Celsius degrees have +/- signs, since it's scalar?
 
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ELLE_AW said:
Why does Celsius degrees have +/- signs, since it's scalar?
How would you recommend temperatures below zero Celsius be indicated?
 
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Scalars can be negative. You are thinking of a magnitude which is strictly non-negative. Temperature is not a magnitude.
 
Dale said:
Scalars can be negative. You are thinking of a magnitude which is strictly non-negative. Temperature is not a magnitude.
Thank you so much for the distinction. That makes perfect sense.
 
ELLE_AW said:
Why does Celsius degrees have +/- signs, since it's scalar?
The celsius scale (also the Fahrenheit scale) uses values that relate to arbitrary points on an absolute temperature scale. That scale starts at Zero K so all temperature values are actually 'in the same direction'.
 
Dale said:
Scalars can be negative. You are thinking of a magnitude which is strictly non-negative. Temperature is not a magnitude.
sophiecentaur said:
The celsius scale (also the Fahrenheit scale) uses values that relate to arbitrary points on an absolute temperature scale. That scale starts at Zero K so all temperature values are actually 'in the same direction'.

Yea, the Kelvin scale makes more intuitive sense to me, but yea the arbitrary nature of that zero point makes sense too, as representing another temperature scale. Thank you!
 
ELLE_AW said:
Yea, the Kelvin scale makes more intuitive sense to me, but yea the arbitrary nature of that zero point makes sense too, as representing another temperature scale. Thank you!

It's not really arbitrary, though. The scale for Celsius was chosen so that 0 was the freezing point and 100 the boiling point of water, two commonly-occurring phenomena in everyday life. Similarly, Fahrenheit's scale was chosen to relate to a human's every day experience. Absolute scales like Kelvin or Rankine are non-negative, which is nice, but they are much harder to intuitively relate to what you experience in life. It's a lot less convenient to talk about freezing occurring at 273.14 K and boiling at 373.14 K.
 
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boneh3ad said:
The scale for Celsius was chosen so that 0 was the freezing point and 100 the boiling point of water

Originally, the reverse. It was changed by Linnaeus (yes, that Linnaeus) after Celsius' death.
 
boneh3ad said:
It's not really arbitrary, though. The scale for Celsius was chosen so that 0 was the freezing point and 100 the boiling point of water, two commonly-occurring phenomena in everyday life. ...

Yes, but in the big picture it is arbitrary -- we could be doing our labs on the planet Zork, where atmospheric pressure is different.

Where I live, water boils at 204F. Oops, I mean 95.6 Celsius.
 
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gmax137 said:
Yes, but in the big picture it is arbitrary -- we could be doing our labs on the planet Zork, where atmospheric pressure is different.

Where I live, water boils at 204F. Oops, I mean 95.6 Celsius.

Still not arbitrary. It has a specific and logical reason.
 
  • #11
It has a specific and logical reason, but it is arbitrary.
Lots of other values could have been used for equally
specific and logical reasons.

-- Jeff, in Minneapolis
 
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  • #12
Vanadium 50 said:
Originally, the reverse. It was changed by Linnaeus (yes, that Linnaeus) after Celsius' death.
You mean 0° used to be the boiling point of water, and 100° was the freezing point? Well then I’m glad it got changed; that’s just confusing.
 
  • #13
boneh3ad said:
It's not really arbitrary, though. The scale for Celsius was chosen so that 0 was the freezing point and 100 the boiling point of water, two commonly-occurring phenomena in everyday life.
If the Celsius scale is "arbitrary", then so is the Kelvin scale. The difference of 1K is still based on boiling and freezing of water.
 
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  • #14
Jeff Root said:
It has a specific and logical reason, but it is arbitrary.
Lots of other values could have been used for equally
specific and logical reasons.

-- Jeff, in Minneapolis

ar·bi·trar·y
/ˈärbəˌtrerē/
adjective
  1. based on random choice or personal whim, rather than any reason or system.

So... not arbitrary.
 
  • #15
boneh3ad said:
So... not arbitrary.
Except for arbitrary definitions of "arbitrary".
 
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