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View Full Version : Google temperature conversion weirdness

Colophon
02-07-2007, 07:34 AM
I just used Google to convert -8ºC into Fahrenheit.

I type in -8c in f and get the answer:
(-8) degrees Celsius = 17.6 degrees Fahrenheit

I noticed Google put the brackets in. Hmm, I thought, what happens if I put the brackets in a different place?

So I type in -(8C) in f and get...
-(8 degrees Celsius) = -965.74 degrees Fahrenheit

What the hell? That's cold. At first I wondered if maybe it was working out 8ºC below absolute zero or something, but no.... absolute zero is only -459ºF or so.

What is Google working out, exactly?

Colophon
02-07-2007, 07:40 AM
Okay, so I figured out what it's doing.

8ºC (in absolute temperature terms) is 281.15 ºC above absolute zero.

And 281.15 ºC below absolute zero would be -554.3 ºC.

And -554.3 ºC equals -965.74 ºF (or would, if such a temperature existed).

But why on Earth does Google interpret it like that?

groman
02-07-2007, 08:01 AM
I think it's a side effect of internal conversion to Kelvin, but it does make sense in a bizarre kind of way. Celsius is not strictly a unit but rather a scale adjustment combined with a unit (a kelvin) -- Celsius, Kelvin and Fahrenheit 0 points do not match up. So just because X degrees Celsius is Y degrees Fahrenheit, -X degrees Celsius is not necessarily -Y degrees Fahrenheit. So not only your unit is different, your scale is different as well. In a way when you write 8 C you are specifying relative temperature interval, it just happens to be relative to a fixed well defined point. -8 C is the same amount in the different direction from that point. Temperature has a relatively well defined 0, and that just happens to not match up with centigrade 0, so -(8 C) is the negative of the temperature above the physical zero, not the relative zero because you are negating your scale as well as your scalar.

:smack: I think I just made it more confusing.

chrisk
02-07-2007, 08:04 AM
I suspect that there's also some other google calculator routines that are getting called, having nothing to do with unit conversion as such, but triggered by the -( ) notation... first evaulate whatever's inside the brackets, and then take the absolute negative of it.