Re: Has the Church ever been wrong?
I was always under the impression that the Church is infallible when it comes to its teachings on the faith and on doctrines. This means that the ENTIRE Magisterium---Pope and Bishops---can't get something wrong. If one Bishop teaches something wrong, then infalliblity can't be called to question. If a Pope teaches something wrong from his own opinion, then infallibility isn't in play here.
If the Pope speaks ex cathedra, then it is infallible. If the Bishops, in union with the Pope, declare something, it is infallible. When either group speaks alone, they are fallible.
In the case of Galileo, it seems like the Pope issued a decree. Papal decrees aren't infallible as they are not ex cathedra. And, infallibility is only involved in issues of the faith. The Church can be and has been fallible in terms of political issues, wars, and science.
Papal bulls/decrees are simply the Pope writing a letter. It carries no weight of dogma or infallibility. They are, however, authoritative. That means that one shouldn't outright disobey it, but that doesn't mean that one can't argue against it. Arguing against a papal decree does NOT make one a non-Catholic, and the words contained within the Papal bull/decree are not infallible dogmas and are subject to change.
I should also add that Papal infallibility is only in effect if the Pope is defining a doctrine that concerns faith or morals. Pope Urban VIII was dealing with science (not faith), and he wasn't defining anything. Papal bulls can be repealed (eg. Pope Benedict XIII's repeal of the Papal bull which stated that smoking was punishable by excommunication). Besides, the doctrine of ex cathedra wasn't even defined when Urban VIII was Pope, so that can't be brought up here (it's not like he used it anyway).