Metallic hydrogen is a potential wonder substance first proposed by Eugene Wigner and Hillard Bell Huntington back in 1935, but since conditions here on Earth are not extreme enough to create it, its existence has remained theoretical — that is, until now.

Harvard scientists Isaac Silvera and Ranga Dias have created metallic hydrogen by squeezing a hydrogen sample with pressures never before produced on Earth, even greater than the pressure that exists at the center of the planet, reports Phys.org.

"This is the holy grail of high-pressure physics," said Silvera. "It's the first-ever sample of metallic hydrogen on Earth, so when you're looking at it, you're looking at something that's never existed before."

They created it using a synthetic diamond that was immaculately polished to remove even the tiniest of imperfections that might weaken it. Since diamond is one of the hardest materials in nature, researchers were able to use it to create pressures greater than 71.7 million pounds-per-square inch, thus transforming solid molecular hydrogen into atomic hydrogen, which is a metal.

This is important because as a metal, hydrogen can function as a superconductor at room temperature. Furthermore, the material is theorized to remain in its metallic state even after the pressure is removed.

"One prediction that's very important is metallic hydrogen is predicted to be meta-stable," explained Silvera. "That means if you take the pressure off, it will stay metallic, similar to the way diamonds form from graphite under intense heat and pressure, but remains a diamond when that pressure and heat is removed."

The work is described in a paper published in the journal Science.

What metallic hydrogen makes possible

It's impossible to understate just how important a stable, room temperature superconductor could be. It could, quite seriously, change the world as we know it. Or at least, it could usher in a new era of technological breakthroughs.

For instance, it would make magnetic levitation for high-speed trains far more feasible, revolutionizing our transportation infrastructure. Electric cars could be made immensely more efficient, and the performance of our electronic devices would be greatly enhanced.

That's just scratching the surface, though. Superconductors have zero resistance, so energy could be stored by maintaining currents in superconducting coils, to be used as needed. Furthermore, since it takes such tremendous pressure to create metallic hydrogen, when it's converted back to molecular hydrogen, all of that energy gets released. In other words, it could potentially create the most powerful rocket propellant known to man, making long-distance space travel more feasible than ever before.

"That would easily allow you to explore the outer planets," Silvera said. "We would be able to put rockets into orbit with only one stage, versus two, and could send up larger payloads, so it could be very important."

Researchers still have some work to do before these technologies can be realized, however. First and foremost, they need to test to make sure that the properties of theoretical metallic hydrogen match up with the properties of the real thing. It's still a remarkable accomplishment either way.

"It's a tremendous achievement, and even if it only exists in this diamond anvil cell at high pressure, it's a very fundamental and transformative discovery," said Silvera.