  In a recently published article [1], Ranga P. Dias & Isaac F. Silvera have
reported the visual evidence of metallic hydrogen concomitantly with its
characterization at a pressure of 495 GPa and low temperatures. We have
expressed serious doubts of such a conclusion when interviewed to comment on
this publication [2,3]. In the following comment, we would like to detail the
reasons, based on experimental evidences obtained by us and by other groups
worldwide that sustain our skepticism. We have identified two main flaws in
this paper, as discussed in details below: the pressure is largely
overestimated; the origin of the sample reflectivity and the analysis of the
reflectance can be seriously questioned.

Other Condensed Matter;Materials Science