Reply #27: It's "possible"

[cosmicaug]

Let's assume that "other gases" means something really, really dense to obtain a limit value. Maybe something like tungsten hexafluoride which would be about 13.1 g/l at STP. That would surely do the job, right? Well, not really. Two thirds of the density of water would be about 667 g/l. Of course, it would be foolish to assume STP with such an atmosphere. So what pressure would it take for a ridiculously dense example, such as tungsten hexafluoride to actually have a density of around 2/3 of water? Using Boyle's law, density would be inversely proportional to pressure giving about 51 atmospheres for the tungsten hexafluoride example (note that tungsten hexafluoride may not even remain a gas at this pressure --I have not checked).

Of course, WF6 is an extreme example meant to illustrate a densest case scenario but it does tell us that you could indeed have an atmosphere as described but that it would have to exist at a pressure greater (probably much greater) than 50 atmospheres. This would be somewhere around 300 atmospheres for CO2 (you could find such a pressure on earth right now under approximately 3 kilometers of water) or even higher for an atmosphere made out of mostly nitrogen. This would only seem plausible to a stupid YEC (assuming they even get this far in their reasoning and are not merely parroting what other YECs have said).