...a factor of gravity and density. The air would weigh more on a cold day than a hot day. as well as near sea level as opposed to on top of a mountain. And in the far reaches of space would not be conci...
There are twelve inches in a foot. Take a look at a ruler, if you have one handy. A ruler is a foot long, and it is divided into inches; this way, you can see how big an inch is.