One of the rarest metals in the universe, metallic hydrogen could solve many energy problems – but has it finally been isolated in the lab? Jon Cartwright tries to sort out claim from counter-claim
Scientists aren’t immune to the allure of rare metals. Isaac Newton’s interest in alchemy is well documented: when the natural philosopher wasn’t laying the groundwork for much of modern physics he was often secretively, obsessively, attempting to turn lead into gold. These days, physicists are hoping to turn a humble element into something yet more precious.
Hydrogen is the lightest of all atoms, not to mention the most abundant, accounting for three-quarters of all the universe’s normal matter. As we commonly know it, hydrogen is a molecular gas – colourless, odourless, mostly harmless and, some might say, rather dull. But under extreme pressure, hydrogen will supposedly turn into one of the rarest metals in the universe, one that is naturally non-existent here on Earth and perhaps only present in the underworlds of gas giants, such as Jupiter. The metal is coveted not just for its rarity, but also because it could turn out to be a stable room-temperature superconductor, and therefore go a great way to solving the world’s energy problems. For over a century physicists have sought metallic hydrogen. Within the past year, however, physicists Isaac Silvera and Ranga Dias (pictured above) at Harvard University in Massachusetts, US, claim they have finally made it, by squeezing hydrogen inside a diamond anvil cell to pressures of nearly five million atmospheres. Is it for real? “If it is true, it is a great achievement, fulfilling a long search for the atomic phase of hydrogen,” says David Ceperley, a theorist at the University of Illinois Urbana–Champaign in the US. “However, there is deep scepticism in the community about their experiment.”
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