Examples13 available
However hard you try, you can't finish it in a week or so.
It would take forever for me to explain everything.
Even if my house catches fire it would soon be put out.
Mathematics is the part of science you could continue to do if you woke up tomorrow and discovered the universe was gone.
Prime numbers are like life; they are completely logical, but impossible to find the rules for, even if you spend all your time thinking about it.