Buoyancy: exactly! I'll admit that phrasing it shortly is sort of misleading, but it does still carry a precise meaning: we're talking of "a mass of 1kg" (in t

Buoyancy: exactly! I'll admit that phrasing it shortly is sort of misleading, but it does still carry a precise meaning: we're talking of "a mass of 1kg" (in the gravitational pull sense) vs "weighs" (the act of measuring the resultant force at rest on a scale, which has to compensate for the gravitational pull as well as buoyancy). "standard conditions" generally means 1kPa, the density of lead is 11.34 g/cm^3, the density of keratin (which feathers are made of) is 1.32 g/cm^3, the density of air is 0.001275 g/cm^3; which give us a difference in Buoyancy amounting to: 0.85 g [1] Which is not that low a difference compared to 1kg. [1] https://www.google.com/search?q=%281kg+%2F+%281.32+g%2Fcm%5E3%29+-+1kg+%2F+%2811.34+g%2Fcm%5E3%29%29+*+0.0012754+g%2Fcm%5E3+in+g&oq=%281kg+%2F+%281.32+g%2Fcm%5E3%29+-+1kg+%2F+%2811.34+g%2Fcm%5E3%29%29+*+0.0012754+g%2Fcm%5E3+in+g https://www.google.com/search?q=%281kg+%2F+%281.32+g%2Fcm%5E...