…I used to beat my wife with lettuce…
Nothing, depends on what geometry you’re using, and either yes or no (whether we can know the answer to that last one is a more interesting question).
Are the Peano axioms consistent?
?
Nah, that was answered. The real question is who put the bop in the bop shu bop shu bop.
What is the exact position and momentum of a given electron?
Not only do you not know, you can and could never know.
“Yes. It’s very safe.”
“Is it safe?” (whirrrrrrrrrrrrr…)
“No! It’s very dangerous!”
“Is it safe?” (zzzzzzzzzzzzz!)
“I don’t know! I can’t tell you if it’s safe or not, I don’t know what it is! AAAAAH!!”
Poor Dustin Hoffman.
Is there any way to know for sure that you’re not trapped in an illusion?
Is there any way to know for sure that you’re not trapped in an illusion?
Ultrafilter’s question, “Are the Peano axioms consistent?” might be answerable, but only if the answer is no. For the record, Peano’s axioms are the commonly used axioms of arithmetic, including mathematical induction. And this remains true of all the mathematical questions that are thought unanswerable, such as is there is a set larger than the set of integers, but smaller than the set of real numbers? It is unanswerable in a commonly used axiomatization of set theory (Zermelo-Frankel, with or without choice), but those axioms might be inconsistent. Assuming they are consistent, there are lots of unanswerable-in-principle questions
42?
Yes I know a humorous answer was given at the end of book three, but in one of the later books Adams hints that the question and the answer can’t exsist in the same universe without the universe being destroyed.
Do I look fat in these pants?
What, me worry?
Dear Sir, I hope you are well? I have…
Can you help me - I can’t send email!
“Does a tree falling in the woods make a sound if no one is their to hear it?”
That’s easily answerable… It’s so late, and I’m having trouble putting it into words. All movement causes a disturbance of air, and that air rushing through space causes friction, which emits energy in the form of sound. When a tree hits the ground and a person is present, that person is simply perceiving the disturbance of air - whether or not he or she is there, there is still by-definition a produced sound.
now, correct me if I’m wrong, but I don’t think there is any way to know for sure that you’re not trapped in an illusion?
The scary thing is that, despite our trying, we still won’t (and probably never will) know all of the unanswerable questions.
Remember: you don’t know what you don’t know. 
