"Computable" is a technical term, meaning that it can be answered if given an unbounded amount of spacetime
Here's my problem with the above- It is ambiguous. For example, a computable number can have infinitely many decimal places so long as there exists a procedure for calculating in finite time any particular decimal place (i.e., if we treat some real number as an infinite sequence we can compute any
nth term in the sequence through finitely many computations). Naturally, for any number with infinitely many different decimal places (i.e., not a rational number), computing the number is impossible: there are infinitely many decimals and so there is no answer. But for any
nth step in the computation, there
is an answer. Hence, computable.
However, a problem that requires an infinite time to compute is not answerable. A computable number, function, set, etc., must be able to halt after finitely many steps. Otherwise, it is not computable. That's one of the important reasons behind the infinite tape and the ordering of arbitrarily many machines. He showed that with any arbitrary number of Turing machines with infinite tape, the problem of determining whether a procedure to find the answer to a problem for which no known explicit procedures exist is not computable. Infinite space mattered because he required arbitrarily long tapes, but infinite time means, in general, that there is no answer. The question is whether or not a problem that requires infinite time can halt at any desired step with an answer the way an infinite number can be computed.