Twice as Hot/Cold? What Does That Mean?

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SUMMARY

The discussion centers on the concept of expressing temperature as "twice as hot" and the implications of using different temperature scales. Participants agree that using Celsius or Fahrenheit lacks a meaningful interpretation of doubling temperature due to their arbitrary zero points. The Kelvin scale is suggested as a more appropriate measure for absolute temperature, as it provides a consistent basis for comparison. Ultimately, the conversation highlights the subjective nature of temperature perception and the confusion surrounding its expression in everyday language.

PREREQUISITES
  • Understanding of temperature scales: Celsius, Fahrenheit, and Kelvin
  • Basic knowledge of thermodynamics and absolute temperature
  • Familiarity with the concept of subjective perception in scientific measurements
  • Awareness of the implications of using arbitrary zero points in measurements
NEXT STEPS
  • Research the differences between Celsius, Fahrenheit, and Kelvin scales
  • Explore the concept of absolute zero and its significance in thermodynamics
  • Learn about the relationship between temperature and energy in physics
  • Investigate how human perception affects the interpretation of temperature changes
USEFUL FOR

This discussion is beneficial for physicists, meteorologists, educators, and anyone interested in the nuances of temperature measurement and perception.

Nick89
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Hi,

I was just wondering, if you say "The temperature today was twice as hot as it was yesterday", in which units are people usually referring?

Degrees Celsius doesn't make any sense, since it is perfectly possible for something to be twice as hot or cold as 0C... For the same reason I don't think degrees Fahrenheit make any sense...
So that leaves Kelvin I suppose? Twice as cold as 0 K would still mean 0 K since you can't go any lower, right?

So if today the temperature is 20 degrees C (roughly 293 K) and tomorrow it's twice as hot, would that mean it would be 293 * 2 = 586 K = 313 degrees C...? This doesn't really make sense to me either.

I suppose it's all about how humans physically interpret temperature? If we sense something to be twice as hot that doesn't mean the temperature is twice as hot in any scale we use, right?So yeah, I was just wondering, is there any 'convention' for this, or does nobody care what twice as hot means? :-p
 
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Nick89 said:
I was just wondering, if you say "The temperature today was twice as hot as it was yesterday", in which units are people usually referring?
When folks use that expression, I don't think it's intended to be taken literally. :wink:
 
Next time someone tells you "it's twice as hot as it was yesterday," ask them what they mean.
 
Here - and we are using Celsius scale only - that will mean something like "it was 10 yesterday, it is 20 today". Or "it was -5 but it is -10". Not exactly, but something like that. No idea how it works if you use Fahrenheit.
 
No reason why you couldn't do the same with Fahrenheit. It was 32 degrees yesterday; today it's 64 degrees. So--even though the units are arbitrary and the zero point is arbitrary--I guess it's OK to say the temperature has doubled! :smile:

(It would be more meaningful if you used the Kelvin scale.)
 
That it can be used same way with F is obvious, it is just beyond my experience - and cultural/language reflexes often cripple logic down :smile:
 
It's meaningless if you aren't on an absolute scale otherwise it would double from 10-20C in Canada but only go up by a third 50-68F in the USA.
 
For most people this meaniglessness doesn't matter, only some eggheads wring hands :wink:
 
only some eggheads wring hands
Thats me!
Our low temperature physics group used to have a sign over the door saying "1million times colder than room temperature" - which always slightly annoyed me as well.
 
  • #10
mgb_phys said:
It's meaningless if you aren't on an absolute scale otherwise it would double from 10-20C in Canada but only go up by a third 50-68F in the USA.

But that's exactly me point :approve:

If you wouldn't have any thermometer and someone asks you something like "how hot do you think it is", and you reply "it's nearly twice as hot as yesterday", then I can't imagine people using the celsius scale mean something completely different than people using the fahrenheit scale... While for your feeling, the temperature doubled, in reality, the temperature (depending on which units used) did not double at all...

I suppose you could look at the energy of the heat, just like you can look at the intensity of a soundwave (if the volume of sound doubles for your feeling, the soundlevel (in dB) has not nearly doubled)... Oh well, I think it's just one of those human things that don't really make sense :P
 

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