Onnes discovery seems clearly not counterfactual. My understanding was that multiple people were quite interested in the question of what happens to the resistance when you cool something down using the new tech of Dewars (invented by Dewar) and liquefied helium. For example, Dewar himself was looking into it! Onnes was motivated by an ongoing research agenda with multiple researchers trying to do the thing he was trying. Note also that it was a very short time between when the tech to cool down enough was invented to when Onnes made his discovery.
Onnes’s was the first to liquefy helium, but he bought the device he used (which had the novel innovation of exploiting the Joule Thomson effect to liquefy gases) from the inventors of the device (Linde Machine, using the Hampson-Linde cycle). Onnes performed an earlier resistance measuring experiment, this time with mercury, and then observed the superconductivity. Both of these seem like they would’ve been done pretty soon by someone else.
Surely others would’ve tried cooling a bunch more metals in the already ongoing quest to understand the resistance at cold temperatures, and then realized the superconductivity in some of them. Mercury, lead, and niobium superconduct at low temperatures—surely someone would’ve tried metals as obvious as mercury and lead. At the very least, observation of the superfluidity of liquid helium should’ve spurned people into cooling random stuff and seeing if anything weird happened.
Onnes discovery seems clearly not counterfactual. My understanding was that multiple people were quite interested in the question of what happens to the resistance when you cool something down using the new tech of Dewars (invented by Dewar) and liquefied helium. For example, Dewar himself was looking into it! Onnes was motivated by an ongoing research agenda with multiple researchers trying to do the thing he was trying. Note also that it was a very short time between when the tech to cool down enough was invented to when Onnes made his discovery.
Onnes’s was the first to liquefy helium, but he bought the device he used (which had the novel innovation of exploiting the Joule Thomson effect to liquefy gases) from the inventors of the device (Linde Machine, using the Hampson-Linde cycle). Onnes performed an earlier resistance measuring experiment, this time with mercury, and then observed the superconductivity. Both of these seem like they would’ve been done pretty soon by someone else.
Surely others would’ve tried cooling a bunch more metals in the already ongoing quest to understand the resistance at cold temperatures, and then realized the superconductivity in some of them. Mercury, lead, and niobium superconduct at low temperatures—surely someone would’ve tried metals as obvious as mercury and lead. At the very least, observation of the superfluidity of liquid helium should’ve spurned people into cooling random stuff and seeing if anything weird happened.