Air weighs… nothing! Or so you might think.
Actually, air weighs a lot. But we don’t think in those terms because it’s all around us and doesn’t seem to weigh anything at all. If it did, it would fall to the ground, no? Well, it kind of does.
As a science fiction author, I am, by nature, air-headed. I have a pretty big noggin with a lot of air in it, so I know, first hand, that it weighs a lot… or maybe it’s just my weighty thoughts. But I do think about how space craft could possibly fly through space, change direction, bank, swerve, and do all the exciting action that we see in movies like Star Wars, or read about in my chosen genre.
As with my blog post on how much clouds weigh, it’s easier to grasp when we contemplate things in volume.
A quick Goolge search reveals that air weighs roughly 0.0807 pounds for one cubic foot at sea level in normal conditions. Infinitesimal, virtually nothing, nearly weightless, you might think, until you quantify it with volume.
Let’s start with something simple, a basketball court, measuring 50 by 100 feet. A one foot layer of 5,000 cubic feet of air weighs 403.5 pounds. Wow! Bet you didn’t know that. But it gets better. A 50 foot layer of air on said BB court weighs 20,175. Whew! Give me some air!
Here are some mind-blowing tid bits. If you were to create a cylinder that could contain the Eiffel Tower, the air would weigh more than the tower itself. There’s roughly 16,093,700 lbs. of metal in that baby. Yet a cylinder of air surrounding it’s dimensions, (1063′ high by 289′ in radius, we’re talking cylinder here), is 279,031,729 cubic feet, and that air weighs a little over 22 million pounds. Shazam!
As big as the stadium is, the Eiffel Tower jumps ahead because of it’s height.
Now, those are mind boggling, no doubt. But it gets more-so when you consider the air pressure of all the atmosphere stacked on top of us. Again, it feels weightless to you and me, but the air pressure at sea level is roughly 14.7 pounds per square inch! You’ve lived with that kind of weight on your shoulders all your life, so you’re used to the burden.
Back to the basketball court. We saw above how much a 50 foot layer of air weighs (20,175 lbs). But how about the layer of air that reaches all the way into space? At 14.7 lbs/sq. inch, there’s 60,000 square inches on that court, or 822,000 lbs of air resting on those boards.
These are amazing enough. Yet, when thinking about all the air that covers the earth, it’s nearly unimaginable.
One square mile is roughly 60,336 inches by 60,336 inches, or about 3.64 billion square inches. Times 14.7, you get 53,514,363,571 lbs. of air pressure covering that one square mile. Earth has 196.9 square miles, so that comes out in the neighborhood of 10,536,978,187,169,280,000 (10.5 sextillion) pounds of air. Sure, sure, air pressure changes at different elevations, and there’s the high and low barometric pressure and all that, but you get the idea.
While all this makes interesting cocktail conversation, it becomes even more important when figuring out how space fighters can maneuver when we transition into density of air. After all, airplanes don’t float like a balloon or blimp. The same principles that allow an Airbus A380, fully loaded, tipping the scales at 1,265,000 pounds, to fly across the world could be applicable to manuevering space. Don’t worry, Luke Skywalker probably didn’t give it much thought either. Check out my next blog to find out.
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