For a human eye with excellent acuity, the maximum theoretical resolution is 50 CPD (1.2 arcminute per line pair, or a 0.35 mm line pair, at 1 m).
...A resolution of 2 arcminutes per line pair, equivalent to a 1 arcminute gap in an optotype, corresponds to 20/20 (normal vision) in humans
If my math is correct then this is 60% worse than the 'excellent' eye; so the figure of 477 ppi at 12 inches is 286.2ppi; so well within the retina display's capability.
It's Apple's OS, they developed it, spend years and millions of $$$ making it - why shouldn't they be allowed to say what machines can and can't run it?
These arguments about "I'd buy a Mac if it had exactly X configuration, but seeing as they don't I'll just pirate it on my own system" have absolutely zero merit. Just because the developers of Windows and Linux have chosen to let you run their OS on any x86 machine, doesn't mean you automatically have the right to run any piece of software you like on your machine.
What I mean by passive detection systems is anything like an optical camera which does not need to emit anything to see something. I am not sure what technologies could be used, but while hiding is a good thing, being able to 'see' is just as important.
An optical camera relies on light coming from or reflect off an object to see it. Light only travels a matter of a few metres underwater, and to hear another vessel (i.e. SONAR) that vessel needs to be emitting some sound; which these submarines are designed to minimise.