[mdom]

While a real explanation doesn't come, google told me that regular exponents are multiplication right, so 9^2 is 81 because 9 times 9 is 81! Negative exponents are the opposite! Because negative. So they're division! And what better to visualize division than fractions! So 9^-2 would be 1 divided by 9 times 9. Or something like that.