Very exciting! For context, here's a nice long article (Aug 2016, 2 months before this arxiv paper came out) on the recent history of attempts to make it, with

Very exciting! For context, here's a nice long article (Aug 2016, 2 months before this arxiv paper came out) on the recent history of attempts to make it, with quotes from author of current paper and others in the field: https://www.sciencenews.org/article/pressure-make-metallic-hydrogen https://www.sciencenews.org/article/pressure-make-metallic-h... > A few months later, Silvera’s group squeezed hydrogen hard enough to make it nearly opaque, though not reflective — not quite a metal. “We think we’re just below the pressure that you need to make metallic hydrogen,” Silvera says. His findings are consistent with Eremets’ new phase, but Silvera disputes Eremets’ speculations of metallicity. “Every time they see something change they call it metallic,” Silvera says. “But they don’t really have evidence of metallic hydrogen.” > All this back and forth may seem chaotic, but it’s also a sign of a swiftly progressing field, the researchers say. “I think it’s very healthy competition,” Gregoryanz says. “When you realize that somebody is getting ahead of you, you work hard.”