What is the average temperature of space?

What is the average temperature of space? Why does it matter? Well, was out having a pint and a laugh and a friend started on this subject. It came betting time, since we had different opinions, both quite sure that we knew the answer. My knowledge was based on some reading of articles made by people who do space research for a living, so I was curious that where he got his info as he has an opionion that is so totally different from mine. Turns out that he was in a job interview (there was a high-paying consultant doing it) and it was one of the questions they asked. They had this random questions section in the interview. He did not know the answer and just out of curiosity, sent for the answer on an email after they turned him down. They replied sayng that -6 degrees Centigrade, or between -3 and -10 was the right answer. I stated that there is no way for that to be the right answer. How could the right answer be about something researched by scientists, between 3 and 10? Around 6? The earth would be warmed by space? How can it ever get to -40 in finland if the space is warmer than that? Wouldn't it warm the cold north? Actually, I said that this is so stupid that the betting is pointless and I'm not taking it. My hand got twisted and the bet was formed, for 20 UK sterling. We then pursued on getting drunk and getting the right answer. I did not call to anyone, as I thought that my friends think that I am an idiot if I call and ask that, as one should naturally know the answer. Others were not so shy and called their relatives and significant others. The thing is, none of them knew. The person keeping the pub or anyone sitting in the pub did not know the answer. All the time they are sure that I am wrong and keep telling me so. They send some texts and people around start googling. All this time I cannot believe that not only they do not know the answer, but none of the persons they called knew the answer. Not only that, they still maintained that I am totally, absolutely wrong? WTF?


Anyways, we had a really nice night debating about this, I got to win and have a wide grin and maybe teach a lesson about betting, knowing things and more than that, second guessing. I second guessed myself, thinking that can I be wrong? I then thought that I cannot be wrong, I simply must be right, or quite near the right answer. Way nearer than what he was with his 6ish Centigrade. My answer was, absolute zero, -273 degrees Centigrade or 0 degrees Kelvin, within some decimals, as there are hot objects in space, heat absorbing objects, paticles and such. But since space is so big, it does not matter on the average. I was not right, but close. Empty space is 0 Kelvin, as there is nothing there, there is nothing to be warm. The thing is that the space is not empty, it has radiation, that you cannot see. The planets, stars and other thingies are just the somewhat visible part. The space has some radiation that is "warmish". I hear that the "warmth" is still remaining from the Big Bang and the space, being so young, has not completely cooled down yet. I still do not know the right answer, as I cannot go to the space and measure it from everywhere to put in my excel and count the average, but I read that the "right" answer can be calculated and the calculations can checked and verified by measurements.
The most often used Q&A is "What is the average temperature of the known universe?" and the most often used answer is 3 Kelvins. This is certainly not right. 2,7 Kelvins is a bit closer, but still not there.

I think that this is a classic case of "Why do we care?" We cannot know what it is, this is quite obviously a question you can anwer differently, and the way you ask the question has a big impact on the right answer.

In fact, I bet you all, that you do not know the answer to the question "What is the temperature of boiling water". You don't know it, trust me. Have you measured it? Why were you so certain about the answer if you have never measured it? Since you have been told the answer so many times? Actually, the question is wrong. You answered and knew the answer to another question. What is temperature when pure water boils on sea level, pressure being one atmosphere? 100 Centigrade Celcius. Rarely is this the case on your kitchen. Even if you had measured it, you are not on sea-level, you might have salt or other matter changing the matter being boiled and hopefully a lid that generates pressure and the kettle is not on sea-level.

You are wrong, the reason being that the answer you give is an answer to the wrong question.
I have measured it, the temperature of my tea kettle and pasta water is... 96-97 C. I guess the reason for this is that water does not want to be 100 degrees, starts to cool down immediately once it reached 100 degrees and stays at about 96-97 C when it is on a boil.