This is probably the most ridiculous comment I've read in the history of this website.

There is no difference in the amount of energy 1 degree Celsius delta and 1 degree Kelvin delta represents.

The only (and I really mean only) difference is how zero energy is defined. It is not possible to have negative energy, and that zero Celsius represents the freezing point of water is an artifact of convenience, not of absolute definition.

Also, the way Kelvin is defined necessitates that both degrees are identical. If 10 degrees Celcius defined the boiling point of water at 1 atmosphere (or whatever the actual definition is) then Kelvin would be smaller by a factor of 10. And this applies to both negative and positive K values.

Ranking, Celsius, Centigrade have the degrees. Kelvin is a base unit, absolute and no degree!

> A 1.8K difference makes sense. A 1.8C difference would be 274.8 kelvin!

I think you're making a math word-problem mistake here, confusing these two:

1. A difference... between [X] and [Y], which is a delta of 1.8°C

2. A difference... between [0°K] and a reading of [1.8°C], which is a delta 274.95°K.

Celsius is not an absolute scale, but that isn't a problem for deltas: (10C - 5C)=5C, (10K-5K)=5K. Celsius is only problematic when multiplying or dividing. 10C is not twice as hot as 5C.

>A 1.8C difference would be 274.8 kelvin!

Categorically and factually incorrect.

A 1.8 degree C different would be 1.8 kelvin. The two degrees have different zero points but one degree Celsius and one degree Kelvin are identical in magnitude.

That makes no sense. A difference between a read of 37C and 38.8C is still 1.8C.

Dude, you are just completely making shit up, and it makes no sense.

So what if Celsius and Kelvin have different 0 points - they are still valid scales and you can talk about differences between 2 measurements.

According to your logic it would be impossible to state that two Fahrenheit measurements differ by some number of degrees F - why, I have no idea.

I'm not entirely sure what point you are trying to make, but this is absolutely false from a scientific perspective.

If you believe otherwise, please provide some citations to your beliefs so we can understand what you are trying to say.

Saying something is false and then asking for citations doesn't seem that helpful to me.

To support your argument, take the following example:

Lets take some water at 273.15 Kelvin and add 1 Kelvin of energy to it. The water is now at 274.15 Kelvin. The difference is of 1 Kelvin.

If we had the same amount of water at 0 degrees Celsius and added 1 Celsius of energy, the water would now be at 1 Celcius.

Converting these values leave us with 273.15 Kelvin and 274.15 Kelvin respectively.

You can repeat this experiment (ignoring latent heat) for any value of Kelvin or Celsius, therefore Kevlin and Celsius are interchangeable in reference to temperature comparasion.

I believe any chemistry or physics textbook will state (possibly indirectly) how temperature deltas work.

But I think it's sufficient to just say that Kelvin and Celsius have the same scale magnitude and just a constant offset.

Kelvin and Celsius use the same unit magnitudes. It would be a 1.8* difference either way.

"A 1.8C difference" expands as "A difference of 1.8C" expands as, and here's the ambiguity, either:

"An absolute difference of 1.8C, or 274.8K, measured between A and B"

or

"A relative difference of 1.8C, or 1.8K, is added/subtracted to A/B in order to reach B/A"

I don't think the context-free variant with K will improve understanding and decrease confusability in this discussion context, but I appreciate the pointer about it in general. I'll take a lot more care around it in a future thread about space apparel!

No it doesn't. The absolute difference[1] of 1.8°C is the same as 1.8K; they have the same scale. The subtraction of values cancels out the offset.

A relative difference[2], usually given in percent change, has problems with a unit that has an offset zero like Celcius, but that isn't what anybody is using here. It's more than simple subtraction; you have to divide by the reference value.

[1] https://en.wikipedia.org/wiki/Absolute_difference#Applicatio... [2] https://en.wikipedia.org/wiki/Relative_difference

To be a stickler, communication requires respect for your audience. The vast majority of everyone understands a 1.8 degree C delta. I would argue that very few people anywhere would understand a temperature delta given in kelvin.

How is expecting readers to not understand what a kelvin is respecting the audience?

You misread.

Most people do not understand temperature on the Kelvin scale. As such, you should not use it to communicate in a general setting such as this.

The same way expecting you understand what a Kelvin is isn't respectful to you.

Taking differences between degrees Celsius values is absolutely fine.

Ratios are undefined because the Celsius scale has no absolute zero while the Kelvin scale has.

See: https://en.wikipedia.org/wiki/Level_of_measurement

You're just confused by terminology. While 1 C is 273 K, 1 degree Celsius is 1 degree Kelvin.

See, a degree is not an absolute unit of measure like a Celsius or a Kelvin, it's a relative difference between two absolute units of measure. When discussing the difference between two separate temperature readings measured in Celsius, degrees Celsius is entirely appropriate.

Think of it like time: there is a difference between meeting at 2:00 and meeting two hours from now.