Our knowledge of physics is uncertain, but it is not inaccurate. Perhaps absolute truth is unattainable, but we can achieve enough truth that it becomes practically equivalent to absolute truth. I haven't read any of Rand's arguments, so it is difficult for me to understand the context, but dismissing an argument on the basis of absolute truth not existing seems a little too convenient.
If our knowledge of as objective a field as Physics is so uncertain, then it makes sense that the state of knowledge in a much more nuanced field like Ethics is near hopeless.
I suspect aliens would run into the same problems as we do, even if they were much smarter than us. I suspect perfect knowledge is unattainable.
Lastly,
>"Do you hold any superstitions (religious or otherwise)? (You probably don't, but it helps to cover all the bases.)"
I don't think the religious would appreciate your reference to their beliefs as "superstition". And no, I am not religious.
However, I don't appreciate your last parenthetical, which implies that I would be offended if you assumed that I was religious. Just yesterday I discovered among Donald Knuth's publications an illustrated book of Bible versus. I have thick enough skin to be lumped among simpletons like Donald Knuth.