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**Temperature: Does it make sense to say something is "twice as cold". (or hot)???**

Here's an old joke:

If the temperature outside is zero degrees, and if it will be twice as cold tomorrow, what will the temperature be?

The joke doesn't specify if the temperature is given in degrees Fahrenheit or degrees Celsius.

Let us therefore assume, we're talking about 0 degrees Fahrenheit.

Using the fact that : [tex]\displaystyle{C = \frac{5}{9}(F - 32)}[/tex]

we can enter [tex]\displaystyle{C = \frac{5}{9}(0 - 32)}[/tex]

and conclude that 0F must equal [tex]\displaystyle{-17\frac{7}{9}}[/tex] degrees Celsius

Double that (twice as cold), and you get [tex]\displaystyle{-35\frac{5}{9}}[/tex] degrees Celsius.

Convert that back to a Fahrenheit temperature using [tex]\displaystyle{F = \frac{9C - 32}{5}}[/tex]

and we conclude that "twice as cold" as 0F is apparently -57.6F.

But what then if some day it is -28.8F, what is "twice as cold" then?