Which one is grammatically correct in the context? or What are the differences among the following s

This one is grammatically correct:


In the first example, the "If" suggests uncertainty so the "will" in "it will be impossible" really sounds better if it is changed to "would".

In the third example the subjunctive mood is being used and is out of place when discussing a scientific theory as it implies wishing for a particular situation or outcome.

All three examples are understandable and the differences are subtle. The second example sounds the best to me.