Why is there such a disparity in the way hair grows on the human head compared to the rest of the body? Apart from our scalps from where hair can grow down to the waist or longer, if left uncut, we...
Nearly all high-flying planes leave contrails. However, I often see small planes, apparently jets, flying at similar high altitudes, which leave no trail. How is this possible?
Water being heavier than air, and clouds being cold, so not warm enough to be lighter than air......what are they doing up there? Why aren't they down here? I don't get it.