Reading a website and I noticed that the author claimed that air pressure is essentially equal to the weight of the atmosphere. I googled that fact and sure enough, everywhere I go there is that statement. But... Caveat. I have no maths or science background, so won't cope with too many equations in answering my question... I assume the concept pressure=weight is a sort of generalisation. Because it does not seem obvious to me that this could be so. Here is a thought experiment. I have a safe of solid steel 1 metre on all sides with an airtight seal. With the safe open and a barometer inside, the air pressure inside will be whatever the extant air pressure is at my location. If I close my safe, there is no longer a column of air acting upon my barometer. True, the atmosphere may be weighing heavily upon my safe's surface, but I see no way for that to affect my barometer. The parcel of air available to exert some kind of vertical pressure is little more than a few cm high. It won't weigh much... What do I not understand?