Can we ever build a death star?
Yes, we can, hypothetically. We already have almost all the technology required to build one (except the clones!). But the financial pressure is so huge that engineers can only dream about it. The cost is difficult to bear: $850 quadrillion, according to the White House's response to the online petition, which is many times the U.S. national debt of about $20 trillion. Also, the amount of steel required to build it is so huge that it would take 830,000 years of Earth's current steel output to create enough metal for the hull of the superstructure alone. Happy dreaming!
If you choose an answer to this question at random, what is the chance you will be correct? a) 25% b) 50% c) 75% d) 25%
It's a paradox. A: Chosen answer = 25%, chance of choosing it = 50%. No match. B: Chosen answer = 50%, chance of choosing it = 25%. No match. C: Chosen answer = 60%, chance of choosing it = 25%. No match. D: Chosen answer = 25%, chance of choosing it = 50%. No match. So the chance of being "correct" in this sense (i.e. of achieving a match) is zero.
How can a light and harmless piece of paper give such painful papercuts?
Because it is about pressure not force. Surface area of paper in contact with your skin is so small that even a slight force against your skin tears it open, just like a knife does.