Re: Kandor
Please remember comics in general, and DC in particular, have never been known for attention to detail. Considering what was shown to be inside the bottle in various stories, the only rational explanation (Rational? in a comic book?) is that Brainiac used his super science to have much more volume inside the bottle that the bottle takes up in outside space.
Otherwise, based on the size of the bottle shown (no more than 3 ft diameter) and the size of the Kandorians who come out the inside of the bottle would be less than 1000 ft!
BTW, the later explanation for Kryptonian super powers is the yellow sun, no mention of gravity. Otherwise, Superman would still have super strength under under a red sun, unless the planet had very high gravity. Also, in several stories non-kryptonians have traveled to Krypton (in the past), and they had no problem with high gravity.