Doesn't fit as there is no "knowledge" tag, which would be required for this answer to explain a part of it. But anyway:
Anyone doing winter sports.
Certain of existence:
Anyone able to do any sports has enough functioning brain cells to be aware of his/her existence.
Best range between -40 and 0:
0 is obvious - ice and snow melts. At around -40C snow stops being slippery.
Some additional explanation for this -40 (you can safely skip it):
It was observed ages ago that snow behaves kind of like sand instead of being nice for sleds when it is cold enough (= around -35 or 40 or somewhere there). Yet interestingly, to this very day we still do not have a final explanation for this phenomenon. People are taught the completely incorrect "pressure melts ice" bullshit, which does not play a role at all. Currently it is believed there are two dominant contributions. Firstly, there is always a thin layer of water on top of ice (until it gets cold enough it is not energetically favorable anymore), secondly, friction heats up and melts the ice a bit - both producing water on which we slip.
Knowing how ice and snow behave lets us make positive improvements to our equipment, technique etc, achieving better results.
Barking up the wrong tree:
You need right wood for the best skis, sleds etc (plus a suitable combination with artificial materials)
No idea for the title.