It's meaningless to add temperatures when the zero level is at +273.
It's like adding years relative to 2010 years ago - it would be meaningless to
add this year - 2010 - with (say) 1666 - the year of the Great Fire of London. It's meaningful to take differences (the Great Fire happened 344 years ago), but not to add. (Unless we converted to some kind of absolute time units e.g. years since the big bang)
I'd say what it's doing - converting to an absolute scale then adding - makes sense.
It's meaningless to add temperatures in any circumstance. You can average temperatures, and you can add amounts of heat energy, but it is semantic garbage to try to add temperatures.
I'd say what it's doing--converting to an absolute scale then adding--is an interesting bug.
I started Deep Thought 2010 years ago. It consisted of two geographically distributed identical units, networked by means of ether. One I put in London, another in Mecca. The former was destroyed in the Great Fire of London, 344 years ago. How many years of processing has Deep Thought finished?
2010 + 1666.
In general, yes, it is pointless to add times. But I wouldn't call it meaningless.
In general, yes, it is pointless to add times. But I wouldn't call it meaningless.
For extremely large values of "in general." The only edge case where it appears to be meaningful is the one you pointed out, where one of your endpoints is the origin of the scale. If you had started Deep Thought at literally any other point in time, the addition would fail.
The addition wouldn't fail; it would just not be very useful. Interval scales do support addition, which comes in handy when you want to, say, calculate the center of mass for interesting events.
What would fail would be trying to determine the factor by which 2010 is later than 1666.
"three degrees hotter" is an interval of three degrees, and not an absolute value along a scale. So you'd take your original temperature and add an interval of 3 degrees to it.
0 degrees Celsius has a heat value (273.15 K). If you double it (i.e. add 0 degrees Celsius to it), you get 546.3 K -- which is 273.15 degrees Celsius.
What it really comes down to is that if you're going to perform math on temperatures for scientific reasons, use Kelvin. And if you're adjusting a temperature by an interval, leave out the units from the math completely.
Hm, well not really. It doesn’t give the answer the user wants to know. They should just convert the second degrees celsius to celsius degrees. (Ideally they should probably also add a ‘Did you mean …’-link with the alternative ála Wolfram Alpha.)
It's like adding years relative to 2010 years ago - it would be meaningless to add this year - 2010 - with (say) 1666 - the year of the Great Fire of London. It's meaningful to take differences (the Great Fire happened 344 years ago), but not to add. (Unless we converted to some kind of absolute time units e.g. years since the big bang)
I'd say what it's doing - converting to an absolute scale then adding - makes sense.