Can a SHA-1 hash be all-zeroes?

Question

Is there any input that SHA-1 will compute to a hex value of fourty-zeros, i.e. \"0000000000000000000000000000000000000000\"?

Answer 1

Yes, it's just incredibly unlikely. I.e. one in 2^160, or 0.00000000000000000000000000000000000000000000006842277657836021%.