[pif]

> If you asked anyone a hundred years ago if they thought they could have real-time communication with someone half way around they world, they would think you were crazy.

It's a different situation: before the radio was invented, people had no idea ho to communicate that far, but they no reason to believe it was not possible at all: it was just a matter of technology. Regarding talking in real time to Mars, already a century ago they had good reasons to consider it impossible: the scientific knowledge of the world is (and already was a century ago) incompatible with faster-than-light cause-effect relation.

One thing is not to know how to do something, another is knowing it to be impossible, short of stunning scientific discoveries.