The answer lies in a lab in China. Scientists from Zhejiang University in Hangzhou, China have created a graphene aerogel that weighs a spritely 0.16 milligrams per cubic centimetre. Zero point one six milligrams.
Although still twice as dense as hydrogen, it’s the first ultra-light material to achieve a mass-to-volume ratio less than helium’s, 0.1786 mg/cm3. It’s super light, and super useful. It can absorb 900 times its own weight in oil (only oil, not water) at a rate of 68.8 grams per second, making it ideal to clean up oil spills, after which both the graphene and oil can be recycled (io9).
When will we create a lighter substance? Onwards!