What’s the Big Deal with Metallic Hydrogen?

Hydrogen is the simplest of elements, comprised of one proton and one electron; everyone knows it exists as a gas in nature, secondary school introductory chemistry taught us it goes “POP” in a test tube when exposed to a flame, and it’s Fisher Price’s “My First Application of Quantum Mechanics” at University level physics. So how does the simplest of elements go about surprising us then?

It can, in theory, be turned into a metal. In parts of the universe where pressures upwards of 1 million kilograms per square centimetre (on Earth, equivalent of 100GPa) exist, Eugene Wigner and Hillard Bell Huntington predicted in 1935 that Hydrogen molecules could come together and form a solid.  A lattice, or stationary grid, of protons will exist with the electrons delocalised, meaning they have the ability to move freely throughout the solid, and be used to conduct electrical currents. The process is similar to how diamonds are formed from carbon.

Laboratory work at Harvard University saw liquid Hydrogen being crushed between two diamond anvils, each coated with aluminium oxide to prevent breaks, at a pressure of 495GPa. This pressure is substantially larger than the pressure found at the centre of Earth (360GPa), and was reported to be a success by Dr. Dias and Dr. Silvera.

Critics have their theories though. At these pressures the reflectivity, the visual evidence that metal Hydrogen exists between the anvils, could be due to the anvil coating. Measurements of the pressure taken by the team are also lacking in detail, which leads to people questioning whether or not the pressures were actually high enough to produce the new metal.

Should the team be correct though, removing the intense pressure could result in the metal relapsing back to its liquid state. Theories do exist that state metallic hydrogen may survive the harshness of Earth’s meagre 101,135KPa pressure, so even if the Harvard experiment proves fruitless, hope is far from lost for the universe’s Number One Element.

So why the big deal? What’s to gain from pursuing this new material? It turns out; quite a bit. One application of this material, if it ever comes to fruition, is the development of a new rocket fuel for space travel. The quantity of energy pumped into its creation is transferred into the lattice of the metallic hydrogen itself. Unravelling the lattice, returning it to regular ol’ gaseous Hydrogen, unleashes the torrent of stored energy, and produce the thrust needed for space travel far more efficiently than fuels in use today. It can also be used here on Earth, in the form of transmission wires. A good portion of electricity generated by all sources, be them fossil or renewable, is lost by the electricity’s travel across wires. Making the wire out of metallic hydrogen however, will result in near perfect transmission, and a far more efficient means of transporting electricity across the globe.

We’ll have to wait for the true results to come through, but we should be quite excited at the idea of this material coming into the world, whether now, or in future.

[Ben Taysum]

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