For nearly 100 years, scientists have dreamed of turning the lightest of all the elements, hydrogen, into a metal.
Now, in a stunning act of modern-day alchemy, scientists at Harvard University have finally succeeded in creating a tiny amount of what is the rarest, and possibly most valuable, material on the planet, they reported in the journal Science.
For metallic hydrogen could theoretically revolutionise technology, enabling the creation of super-fast computers, high-speed levitating trains and ultra-efficient vehicles and dramatically improving almost anything involving electricity.
And it could also allow humanity to explore outer space as never before.
But the prospect of this bright future could be at risk if the scientists’ next step – to establish whether the metal is stable at normal pressures and temperatures – fails to go as hoped.
Professor Isaac Silvera, who made the breakthrough with Dr Ranga Dias, said: “This is the holy grail of high-pressure physics.
“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.”
At the moment the tiny piece of metal can only be seen through two diamonds that were used to crush liquid hydrogen at a temperature far below freezing.
The amount of pressure needed was immense – more than is found at the centre of the Earth.
The sample has remained trapped in this astonishing grip, but sometime in the next few weeks, the researchers plan to carefully ease the pressure.
According to one theory, metallic hydrogen will be stable at room temperature – a prediction that Professor Silvera said was “very important”.
“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,” he said.
If this is true, then its properties as a super-conductor could dramatically improve anything that uses electricity.
“As much as 15 per cent of energy is lost to dissipation during transmission, so if you could make wires from this material and use them in the electrical grid, it could change that story,” the scientist said.
And metallic hydrogen could also transform humanity’s efforts to explore our solar system by providing a form of rocket fuel nearly four times more powerful than the best available today.
“It takes a tremendous amount of energy to make metallic hydrogen,” Professor Silvera said.
“And if you convert it back to molecular hydrogen, all that energy is released, so it would make it the most powerful rocket propellant known to man, and could revolutionize rocketry.
“That would easily allow you to explore the outer planets.
“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.”
However some scientists have theorised that metallic hydrogen will be unstable on its surface and so would gradually decay.
Asked what he thought would happen, Professor Silvera said: “I don’t want to guess, I want to do the experiment.”
But it could be a moment almost as exciting as the time the researchers first realised what they had created.
“Ranga was running the experiment, and we thought we might get there, but when he called me and said, ‘The sample is shining’, I went running down there, and it was metallic hydrogen.
“I immediately said we have to make the measurements to confirm it, so we rearranged the lab ... and that's what we did.
“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.”
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