PRIME NUMBERS
Mathematician: 3 is a prime, 5 is a prime, 7 is a prime, and by induction - every odd integer higher than 2 is a prime.
Professor: 3 is prime, 5 is prime, 7 is prime, and the rest are left as an exercise for the student.
Physicist: 3 is a prime, 5 is a prime, 7 is a prime...