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

Without any knowledge of SHA-1 internals, I don't see why any particular value should be impossible (unless explicitly stated in the description of the algorithm). An all-zero value is no more or less probable than any other specific value.