Two physicists’ claim that they successfully crushed hydrogen gas under immense pressure to turn it into a shiny metal has recently created a lot of noise in the scientific community worldwide. Understandably so — after all, this is a feat that scientists have been trying to pull off for more than eight decades now with almost no success to show off.

So, triumphant as the mood may have been in the labs of Ranga Dias and Isaac Silvera — the two physicists who conducted the experiment — not everyone seems convinced. In fact, skepticism abounds about the experiment’s results among other researchers.

Dias and Silvera, both physicists at Harvard University in Cambridge Massachusetts, first posted a report of their test results on the arXiv preprint server back in October 2016 which immediately attracted criticism from several researchers. A peer-reviewed version of the study was published in the journal Science on January 26, although skeptics are now saying that it includes little new information.

According to Dias and Silvera, they squeezed the hydrogen sample at a greater pressure than the other researchers before they had managed by using an anvil that fits inside a cryostat. This setup enabled the duo to cool the gas just above absolute zero. Apart from that, they also found a better way to polish the tips of their diamonds that played a key role in removing irregularities that could damage the gems. Following this, they increased the pressure all the way up to 495 Gpa which is about five million times greater than the atmospheric pressure at sea level.

Worth noting, this is not the first ever a time when scientists claimed to have discovered metallic hydrogen. In 2012, a team of German scientists made similar claims before being subject to widespread criticism. The researchers eventually regretted the sheer boldness of their announcement saying that their paper should have made it clear that they “might have” created metallic hydrogen, according to Nature.

As a matter of fact, the same issues that caused the scientific community to question the ‘discovery’ by the German researchers are also visible in the work of Dias and Silvera.

“I don’t think the paper is convincing at all,” Paul Loubeyre, a physicist at France’s Atomic Energy Commission in Bruyères-le-Châtel, told Nature regarding this discovery.

“If they want to be convincing, they have to redo the measurement, really measuring the evolution of pressure,” added Loubeyre. “Then they have to show that, in this pressure range, the alumina is not becoming metallic.”

In their defence, Silvera stated that he only wanted to inform the scientific community about their test results before proceeding further with the confirmation tests.