Physicists are crushing it — hydrogen, that is. Squeezing the chemical element to extremely high pressure transforms it into a metal, a trio of researchers claims.

The purported metallic hydrogen appeared at a pressure more than 4 million times that of Earth’s atmosphere, the scientists report June 13 at If confirmed, the achievement would fulfill a long-standing quest to produce the elusive metal, first predicted in the 1930s to exist.

The work has yet to undergo peer review. But it is “definitely a very substantial step ahead” of previous research, says physicist Alexander Goncharov of the Carnegie Institution for Science in Washington, D.C., who was not involved with the study. “I think it’s quite conclusive it is metallic.”

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