3 ms·

How would you convert between Kelvin and Celsius if temperatures couldn't be added?

defrost 3y ago
What does it mean to add temperatures though (serious question)? Eg: Suppose (one of many subtly different scenarios) you have 1 kg of iron at a constant temperature of 20 C and 5 kg of Aluminium at a constant temperature of 15 C. What does it mean to add those temperatures?
- sheepshear 3y ago
  You tell me. Units help describe what you modeled, they can't stop you from modeling nonsense. I heated up your iron by 4 degrees and now it's 20C+4C=24C. I modeled the physical process of heating and the units provide some additional information about that.
  - defrost 3y ago
    > I heated up your iron by 4 degrees and what happened when you applied the same amount of heat to the greater mass of Aluminium? What's the difference between intensive properties (tempreture, pressure, density) and extensive properties, such as mass or volume?
    - sheepshear 3y ago
      Again, you tell me. Units have no meaning without the context of what you're modeling. I can model the average temperature of your pieces of metal as (20C+15C)/2=17.5C.
      - ttoinou 3y ago
        Units have no meaning without the context of what you're modeling. I fully agree with that statement ! But some addition of units are widely accepted because their associated model is almost universal on earth, let's say adding mass (kg) of two different objects
        sheepshear 3y ago
        Yes, that's why we're having this conversation. It's so common that some people reasonably infer a stronger connection between units and physics.
    - TRiG_Ireland 3y ago
      As a vague intuition, I think of temperature as some sort of "heat density". It's not right, but it helps.
  - ttoinou 3y ago
    You can move the numerical value by 4 but it doesnt mean you can add Temperatures You're correct though that as long as you have a very specific working model, you can add Temperatures thanks to it. But that model doesnt propagate to the rest of physics
    - deleted 3y ago
      [deleted]
    - sheepshear 3y ago
      [dead]
  - kahirsch 3y ago
    The 4C there is not really a temperature, though. It's a difference in temperature. I guess that's a limitation of dimensional analysis, since they both have the same units and dimensions.
    - sheepshear 3y ago
      Exactly, 4C is a quantity with temperature units. Units have no semantic meaning without context. Dimensioned quantities have the semantic meaning that you give them.
ttoinou 3y ago
Physicists use the more correct Kelvin scale and you can have conversion functions between Kelvin and others less correct units

What does it mean to add temperatures though (serious question)? Eg: Suppose (one of many subtly different scenarios) you have 1 kg of iron at a constant temperature of 20 C and 5 kg of Aluminium at a constant temperature of 15 C. What does it mean to add those temperatures?

sheepshear 3y ago
You tell me. Units help describe what you modeled, they can't stop you from modeling nonsense. I heated up your iron by 4 degrees and now it's 20C+4C=24C. I modeled the physical process of heating and the units provide some additional information about that.
- defrost 3y ago
  > I heated up your iron by 4 degrees and what happened when you applied the same amount of heat to the greater mass of Aluminium? What's the difference between intensive properties (tempreture, pressure, density) and extensive properties, such as mass or volume?
  - sheepshear 3y ago
    Again, you tell me. Units have no meaning without the context of what you're modeling. I can model the average temperature of your pieces of metal as (20C+15C)/2=17.5C.
    - ttoinou 3y ago
      Units have no meaning without the context of what you're modeling. I fully agree with that statement ! But some addition of units are widely accepted because their associated model is almost universal on earth, let's say adding mass (kg) of two different objects
      - sheepshear 3y ago
        Yes, that's why we're having this conversation. It's so common that some people reasonably infer a stronger connection between units and physics.
  - TRiG_Ireland 3y ago
    As a vague intuition, I think of temperature as some sort of "heat density". It's not right, but it helps.
- ttoinou 3y ago
  You can move the numerical value by 4 but it doesnt mean you can add Temperatures You're correct though that as long as you have a very specific working model, you can add Temperatures thanks to it. But that model doesnt propagate to the rest of physics
  - deleted 3y ago
    [deleted]
  - sheepshear 3y ago
    [dead]
- kahirsch 3y ago
  The 4C there is not really a temperature, though. It's a difference in temperature. I guess that's a limitation of dimensional analysis, since they both have the same units and dimensions.
  - sheepshear 3y ago
    Exactly, 4C is a quantity with temperature units. Units have no semantic meaning without context. Dimensioned quantities have the semantic meaning that you give them.

ttoinou 3y ago

Physicists use the more correct Kelvin scale and you can have conversion functions between Kelvin and others less correct units