Does the 0.9mg/cm^3 number seem strange? The density of air is about 1.2mg/cm^3 at STP[1]. Can it be less dense than air? Wouldn't that make it float?
According to wikipedia the lowest density frozen smoke has a density of 1 mg/cm3 (not including air!), which is just slightly more than this material.
The 4 mg/cm3 number in the article is incorrect (I wrote to them to let them know).
Technically you also have to account for the slight buoyancy the metal has in air (but it's far below the error margin so it's ignored).
Basically on earth when you weigh things you are measuring weight, even if you say grams (which are supposed to be mass).
If you want true mass you have three choices:
1. Weigh in vacuum.
2. Use a scale that shakes the material on a spring and measure the frequency (i.e. measure inertia).
3. Calculate the volume of the material, calculate the weight of air of that volume and add that weight to your measured weight.
No one ever does this since it doesn't matter. But if you want to be exact....
But I don't know if the material is strong enough to result air pressure if it was shrink wrapped (i.e. would the air pressure squish it?)
Awesome.
The Hindenburg used 200,000m^3 of hydrogen (generating a lifting force of approx. 215,000kg. Net useful load was only 10,000kg.
Also compared to a modern blimp the Hindenburg an ancient design that's been far surpassed. A modern Zeppelin is much closer to 20% lift to weight ratio than 5 for the Hindenburg despite using less efficient helium gas. Their maximum permitted takeoff weight is 10,690 kg, with a payload of 1,900 kg.(http://en.wikipedia.org/wiki/Zeppelin_NT)
Weight of air in air is zero.