You don’t have to explain Newton or Einstein physics to show that you are intelligent.
Just list a series of prime numbers (1,2,3,5,7,11,13,17,19 etc.). That list is just as valid here as across the universe, or as moving from the earth at the speed of light. It deals with real integers, base 10, but could be binary or octal or base 17.
On the other hand, Newton/Einstein still boggles the mind.
Euclid's proof of the infinitude of primes is a good introduction to the beauty of mathematics.
Also this: let P be any point on a circle. Lines drawn from the endpoints of a diameter line to P always make a right angle. Wonderful theorem.