By Tamara Alliot, MMTA
Last month, Harvard University scientists claimed in the journal Science to have produced metallic hydrogen, a substance never before seen on earth. This marks the pinnacle of a theory first put forward in 1935 on theoretical grounds by Eugene Wigner and Hillard Bell Huntington.
Metallic hydrogen could revolutionise technology, enabling the creation of super-fast computers, high-speed levitating trains and ultra-efficient vehicles as well as dramatically improving almost anything involving electricity, due to its super-conducting properties. Approximately 15% of energy is lost to dissipation during transmission, so if you could make wires from metallic hydrogen, electrical grid efficiencies would be massively improved.
Humanity’s desire to explore outer space could also be one step closer. Converting the metallic hydrogen back to its molecular form would release a huge amount of energy, making it the most powerful propellant ever, four times more powerful than the best available today. This would revolutionise rocket technology and allow humans to travel further and faster than ever before.
But first, the scientists need to establish whether the metal is stable at normal pressures and temperatures. For the moment, the metal is trapped between the grip of the two diamonds used in an anvil to crush the liquid hydrogen at a temperature far below freezing. The pressure used was more than that found at the centre of the earth.
The scientists plan to ease the pressure on the metallic hydrogen over the next few weeks with the hope that similar to the way diamonds form from graphite under intense heat and pressure, but remain diamonds when that pressure and heat is removed, the hydrogen will stay metallic in normal conditions.
The scientists say that they have confirmed the substance is metallic hydrogen by performing various measurements, and due to its shiny metallic appearance. Others, however, believe that the substance may be something else.
Those casting doubts on the discovery say that the substance could easily not be metallic hydrogen at all.
In October 2016, the Harvard researchers first posted their work to arXiv, a website that collects scientific studies before they are published through peer-reviewed journals. At that point it attracted huge amounts of criticism from other scientists who argued that it was based on a mistake. Nonetheless the paper went on to be published in Science in January.
One problem is that the scientists cannot show off the piece of metal because it is still stuck between the jaws of the anvil, and they say that removing it might cause it to disappear entirely. Though the Harvard researchers believe that the material they can see crushed in the anvil is metallic hydrogen, without access to the sample, this cannot be a definitive conclusion.
Other experts have said that the shininess may be something else entirely, like aluminium oxide, which is known to coat the diamonds that sit in the anvil and may become shiny under high pressure.
Even before this particular paper was criticised, other researchers have criticised the lab’s approach and methods, arguing that it could lead to false positives.
Scientists have also questioned why the team published their results before they have taken the material out of the anvil, but the researchers claimed in press materials that they had done so in order to publicise their “breakthrough event”, and that further experiments would shed more light
The criticisms could be down to scientific jealousy or genuine concerns – time will tell!