What kinds of questions can be answered by science?

Scientific methods are usually applied to questions in any of the physical sciences, where it is possible to observe natural phenomena of various kinds and to make hypotheses about how systems work. For most sciences, tests can be constructed that 'control' one or more of the variables observed so that inferences can be made about how the control of these variables has affected the variable of interest. Direct experimentation is not possible in fields like astronomy, but with very sophisticated means of observing the heavens, important knowledge can be gained.

One aspect of scientific method is that once a hypothesis is made, one can begin asking questions about how the truth or falsity of the hypothesis will affect other parts of the system, and observing those parts then refutes or gives support to the hypothesis. Even though astronomy does not easily lend itself to experimentation, this concept of hypothesis testing is still a very powerful astronomical tool. Or you can ignore all of that because the answer you are looking for is bioethical. :]