
0 degrees celsius + 0 degrees celsius -  - iamelgringo
http://www.google.com/search?hl=en&client=firefox-a&hs=2VC&pwst=1&rls=Palemoon:en-US:unofficial&nfpr=1&&sa=X&ei=c_JpTP6_GoK88gaZgOmyBA&ved=0CBYQBSgA&q=0+degrees+celsius+%2B+0+degrees+celsius&spell=1
======
_delirium
It looks like it must be using kelvin as its canonical units:

    
    
      0C + 0C = 273.15 K + 273.15 K = 546.3 K = 273.15 C
    

The weirdness is that conversions like that don't work for units that have
different zero points. Perhaps addition of temperatures isn't really well
defined? If 273.15 K + 273.15 K does _not_ equal 0 C + 0 C, despite 273.15 K =
0 C, it's not clear what addition "means" in this context.

One restricted form of addition that makes sense (which maybe is what's
intended?) is to consider the 1st temperature an actual temperature, and the
2nd temperature a temperature _difference_ in units of degrees-C (or
degrees-K, or degrees-F). So e.g.:

    
    
      "5 C warmer than 30 C"
      = 30 C + 5 C
      = 303.15 K + 5 K
      = 308.15 K
      = 35 C
    

But then addition isn't commutative. The problem is that "degrees C" is
overloaded here, to mean both a position on a scale, and the size of a unit on
that scale, with no conventional short way of distinguishing which one you
mean (which is one reason Kelvin was invented, since things aren't ambiguous
if you put absolute zero at 0 K).

~~~
nixme
Google can actually differentiate between the two meanings: degrees Celsius
and _Celsius degrees_.

As you explained, the query posed by the title is meaningless, but 0 degrees
Celsius + 0 _Celsius degrees_ is handled correctly:
[http://www.google.com/search?&q=0+degrees+celsius+%2B+0+...](http://www.google.com/search?&q=0+degrees+celsius+%2B+0+celsius+degrees)

~~~
_delirium
Ah, that's pretty interesting. It makes sense when you read the two phrasings
next to each other, but it does seem like a pretty subtle wording difference.
I think in practice people tend to differentiate which one is meant by context
more than by "degrees Celsius" versus "Celsius degrees" being used
consistently.

Should Google should convert the query somehow? It seems like adding two
temperatures in degrees Celsius is something that never really makes sense (or
subtracting, multiplying, or dividing them), so faithfully executing it like
they currently do is rarely what's intended.

~~~
ugh
They should convert the query because that’s exactly what people want to know
when they type in those kinds of queries.

~~~
bruceboughton
>> when they type in those kinds of queries

If I wanted to know 50 degrees Celsius + 35 Celsius degrees, I would probably
omit the units and just ask for 50 + 35. I find it unlikely that many users
actually run into this problem.

~~~
ugh
It’s no big deal, sure.

------
mhansen
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.

~~~
jcdreads
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.

~~~
alextgordon
Yes, temperature addition is garbage, but the addition of an interval to a
temperature is not. Consider:

    
    
        "It was 20 °C yesterday and someone told me it's 10 °C
         hotter today. What temperature is it?"
    

The difficulty comes when you try to write that out using addition. This is OK

    
    
        "10°C + 20°C"
    

because all of the units share the same null point so there is an _implicit_
null point at 273.15 K.

This is not OK:

    
    
        "293.15 K + 10 °C"
    

because the null point could be either 0 K or 273.15 K.

If I were google I'd just show two answers in this case:

    
    
        "10 °C hotter than 293.15 K = 303.15 K
        "293.15 K hotter than 10 °C = 303.15 °C"

------
cperciva
Looks right to me. Asking for 0 degrees celsius + 0 degrees celsius, or put
another way, "what's twice as hot as freezing water?", is profoundly
nonsensical, but 273.15 degrees celsius is the closest you can get to a
sensible answer.

------
DrStalker
Ever tried to add two Unix Time values together? The results may look weird,
but make sense if you know what you're actually adding.

Same here.

------
rincewind
The question is meaningless but google answers it in the best possible way

~~~
tome
Arguably it oughtn't to answer it at all.

It's a bit like asking "Where do I end up if I start at Alpha Centurai and go
one light year east?".

------
poundy
Wolfram Alpha beats Google on this!
[http://www.wolframalpha.com/input/?i=0+degrees+celsius+-+0+d...](http://www.wolframalpha.com/input/?i=0+degrees+celsius+-+0+degrees+celsius)

~~~
ars
No it doesn't:
[http://www.wolframalpha.com/input/?i=0+degrees+celsius+%2B+0...](http://www.wolframalpha.com/input/?i=0+degrees+celsius+%2B+0+degrees+F)

------
Twisol
It sure looks really bizzare, but here it is broken down...

    
    
        "0 degrees celsius in kelvin"
          -> 0 degrees Celsius = 273.15 kelvin
        "273.15 kelvin + 273.15 kelvin in degrees Celsius"
          -> (273.15 kelvin) + (273.15 kelvin) = 273.15 degrees Celsius
    

Hence:

    
    
        "0 degrees celsius + 0 degrees celsius"
          -> (0 degrees Celsius) + (0 degrees Celsius) = 273.15 degrees Celsius

------
Marticus
Moral of the story: Google is a bunch of cheeky bastards.

It took me a while to understand the reasoning behind that as points on a
scale versus actual temperature values ("Celsius degrees" versus "degrees
Celsius," respectively).

Googling "0 Celsius degrees + 0 Celsius degrees" returns 0 Kelvin, which would
be expected given the technicality in wording.

------
billhasmail
Whether "degrees Celsius" refers to a point on the Celsius scale or an
interval is ambiguous and is usually determined by context. Although attempts
at conventions have existed the effect of typing rather than writing was not
considered when they were created and so those conventions are largely
ignored. In this case there is no context so google uses "degrees celsius" and
"celsius degrees" to distinguish between a scale point and an interval which
is a nice natural language solution in my opinion.

To better see what is happening try:

    
    
      0 degrees celsius + 10 celsius degrees
      0 degrees celsius + 10 degrees celsius
      0 celsius degrees + 10 celsius degrees

------
brisance
WolframAlpha gets it right

[http://www.wolframalpha.com/input/?i=0%20degrees%20celsius%2...](http://www.wolframalpha.com/input/?i=0%20degrees%20celsius%20%2B%200%20degrees%20celsius)

~~~
syncsynchalt
Not really. Google's answer is correct, in as much as it can be without
mentioning the materials involved.

------
doki_pen
If you take the absolute temperatures of 0 C in actual heat and add them
together, you would have a cumulative heat of 273.15 C. Makes perfect sense.

------
Myrth
0 degrees celsius - 0 degrees celsius
[http://www.google.com/search?q=0+degrees+celsius+-+0+degrees...](http://www.google.com/search?q=0+degrees+celsius+-+0+degrees+celsius)

------
danielrhodes
Even more confusing:

[http://www.google.com/search?aq=f&ie=UTF-8&q=0+degre...](http://www.google.com/search?aq=f&ie=UTF-8&q=0+degrees+fahrenheit+%2B+0+degrees+fahrenheit)

------
TWAndrews
Seems like arthmatic with temperatures is just broken. This querey: "5 degrees
c + 1 degree f in fahrenheit" yields: "501.67 degrees Fahrenheit"

------
praptak
Yeah, "It is twice as hot today as it was yesterday."

------
dstein
As a rant, it annoys me to no end that C is the SI unit for Coulomb, yet
everyone uses C as Celcius. Someone should fix that.

~~~
slug
Well, afaik, people use ºC and not just C.

------
revolvingcur
I didn't get correct answers for any of the "temperature math" problems I gave
it. Something's screwy on the back end.

------
balding_n_tired
Well, shoot, with enough ice cubes we can reverse global warming.

------
mataap
Temperature is an intensive quantity, not an extensive quantity.

------
hippich
what you expect is to add 0 temperature difference to 0 temperature value.
What it actually calculate - sum of two temperature values. it's matter of
notation imho

------
Vulture
Nice finding, now try to tell them

------
loyd
Is this a bug or a joke?

~~~
keyle
It looks more like a bug. That, or it's a not funny joke.

------
hc
<http://en.wikipedia.org/wiki/Affine_space>

------
cemerick
Stunning and just a little bit sad that something like this hits #2 (almost
surely #1 soon).

~~~
praptak
How about upmodding some of the competing links from the top page or, better
yet, <http://news.ycombinator.com/newest> ?

------
JangoSteve
Digging a little deeper...

    
    
      (0 degrees Celsius) + (0 degrees Celsius) - (0 degrees Celsius) = 0 degrees Celsius
    
      (0 degrees Celsius) - (0 degrees Celsius) = 0 kelvin
    
      (0 degrees Celsius) + (0 kelvin) = 0 degrees Celsius
    

The last 2 of the 3 are wrong, so I'd say this is definitley a bug.

EDIT: I think I figured it out. It's converting everything after the first
temperature to Kelvin, without converting the first temp to Kelvin, and then
just doing the arithmetic on the numbers...

    
    
      0C + 0C => 0C + 273K => 0 + 273 = 273
    
      0C + 0C - 0C => 0 + 273 - 273 = 0
    
      0C - 0C => 0 - 273 = -273 = 0K (ok, weird this one then converts back to K)
    
      0C + 0K => 0 + 0 = 0
    

EDIT 2: While this does match the results seen by google, I think _delirium's
solution is more likely the reason.

~~~
fleitz
0C - 0C => 0 - 273 = -273 = 0K (ok, weird this one then converts back to K)

Your math/logic is wrong, (A - A) => (B - A) you converted 0C to both 0 and
273.

Convert everything to Kelvin and it all makes sense. It's non-intuitive
because 0C indicates a positive amount of energy rather than no energy as 0K
does.

~~~
JangoSteve
If you read my comment leading up to that, you'd see why I did it that way.
But I agree with the other comment that it's more likely Google is just
converting everything to Kelvin as it's canonical calculating form.

