Anything that you can see, which isn't producing its own light is reflecting light from somewhere else; that's how come you can see it. The moon (for instance) is reflecting light from the sun down to earth, which is why you can see it.  Do you have a cat? It is reflecting light from the chandelier … Read more

Its about 34 feet. There are several smart answers concerning Standard Temperature/Pressure, sea level, relative/absolute pressure etc, but for considering an open head in plumbing needed to add an extra 1 bar to the already existing 1 bar of atmospheric pressure all around us, then the answer is that the head needs to be about … Read more

Jlarson, You're right so long as you're thinking about the absolute pressure. In that case (Assuming we're at sea level) you have the weight of the column of air above you which is about   14.696 pounds psi, approx. 1 Bar. en.wikipedia.org Now if we add to that a column of 4 degrees C water 406.782 … Read more