First discovered by Chinese scientists in 2013, graphene aerogel was considered the lightest material in existence, less dense than air itself, or helium for that matter. Also called aerographene, it’s made of carbon nanotubes bonded together in a super-porous structure, like a sponge.

Technically a solid, it acts more like a 3D gas; you can compress it, and it springs back into shape. A chunk of graphene aerogel can balance on a blade of grass. The holes naturally fill up with air, so it doesn’t float away, unless there’s a good breeze.

But what if you could fill the holes with… nothing? Scientists have now created a carbon nano-sponge, where the gaps between the atoms are too small for molecules of air to get in. They are called vacancies.

“We started with a carbon-nitrogen alloy,” said Prof Zhao, “then we electrochemically expelled the nitrogen ions, leaving us with a lattice full of atomic vacuums. It’s the only true solid that’s lighter than air!”

Future applications for this wonder material are endless. Naturally buoyant material that floats in water or air could be used for boats, aircraft or self-supporting structures. Imagine a hover board that hovers without power! At this stage the nano-sponge has only been produced in minute quantities in the lab, but its ability to float in air has already been described as ‘gravity-defying.’

With further refinement, this unique carbon structure might be able to act as an atomic filter; for example, generating oxygen from water by stripping out the hydrogen atoms. Its quantum properties are yet to be explored.

When asked whether they had come up with a suitable name for the material, Prof Zhao replied: “Oh, that was easy. It’s called ‘nothing’!”