Wanna try something? Stand in front of a radiator with a window sill above it, place your hands behind your back (ask a local seamstress to sew them into your back pockets if you lack courage), and fall forward. Pretty cool huh? You've just demonstrated man's innate survival mechanism, which is the reason no-one ever dies.
It probably all happened too quickly for you to take in, so I'll explain what just happened. You stood in exactly the right place - a subconscious thing - which meant you hit your head on the edge of the radiator, knocking you out instantly and anaesthetically. Miss the radiator entirely and you're going to land right on your nose, and fully conscious. Hit too much of the radiator and it'll snap your neck back, which can rip your throat open at the front, and will drop your head right on the chin, splitting it straight down the middle. Hit it in exactly the right place, as everyone always does, and the weight will be dispersed evenly throughout your face, and you wouldn't feel a thing even if you were conscious.
Try and measure where you should stand to fall, and you'll fail painfully; there are too many unquantifiable factors, like slouch quotient, neck flexibility and fearful tensing. Can't be done. Try and get it right and you'll get it wrong, but let yourself fall without thinking about it and you'll be safe. The thoughtless shall inherit the earth from the people who died by thinking.
The reason for a radiator below a window sill is yet another test, this time of a collective consciousness, even though you have to be unconscious to prove it. It takes even more accuracy - but again, accuracy that everyone has - to miss the sill but hit the radiator, than it does to hit the radiator and fall evenly on your face. Hit the sill and you'll thud and bleed in private. Hit the radiator and the clang will resonate through the central heating system, bringing concerned onlookers from rooms around who can treat you with frozen plasters from the freezer. Clear enough proof of a collective consciousness for me, and a vindication for those convicted of the torture and burning of godless heretics without central heating. Doubt? Have a little faith. Try it.