Shannon and I once theorized about what exactly lies beyond the heliopause, not in terms of stars and galaxies, but more in the sense of the laws of physics themselves. In the near future, Voyager 1 may very well make the first extra-solar radio transmission back to Earth. How much do we really know about how the universe works, though? There is much we don't yet know or understand about everyday things we take for granted, such as electricity, electro-magnetism, et cetera.
Just as a quick example, we all know that electricity (more specifically, electrical current) is the motion of negatively-charged electrons around an electrical circuit, but do we really know what drives electrons to behave in this way? What ever this driving force turns out to be, what if it's a phenomenon that can only exist as a result of certain attributes of fields produced by our sun? Many scientists agree that the sun is the engine driving our solar system, and if--or rather, when it eventually dies, the rest of the solar system will also come to a grinding halt. Planetary orbits will eventually slow and stop, as will their axial rotation, and even the cores of the most massive planetary bodies will shut down.
So then, if the physical well-being of our very solar system is so heavily dependent on the nuclear engine at its center, who is to say what will happen when even the most insignificant of man-made machines eventually travels beyond the reach of our sun's powerful influence?
I'll start with electricity, since I have touched on the subject already. It should be obvious that if the existence of electricity depends on a driving force as powerful as our sun, then when any electrically powered machine breaks free of its influence it would shut down. We're not talking power sources here, we're talking about that force that causes electrons to move from one end of a circuit to another. What if, without the sun's power electrons simply cannot move from one point to another?
If our theory is correct, Voyager 1 and 2, as well as Pioneer 10, 11, and any other spacecraft making the voyage beyond our solar system are all doomed to failure. In a few years, when Voyager 1 finally exits the heliopause, we may very well receive a truncated message from the craft as its systems all shut down. NASA scientists will likely be rather perplexed, and may eventually write it off as a system failure. Did we miscalculate something? they might wonder. When the rest of those space probes go out of commission at approximately the same distance from the sun (during or after leaving the heliopause), scientists will be hard-pressed to explain why several unmanned probes have all gone dead under the same circumstances.
Back to the subject at hand, what other ill-fates could this theory propose? Well, take into account the fact that our own organic brains and nervous systems operate on the fundamentals of electricity and you open up a whole new can of worms. Apply this theory to that can of worms and you get a whole lot of dead worms. If electricity cannot exist outside of the heliopause, neither can life in such a scenario. That is unless life can function without electricity. As far as we know, it can't.
So where do we stand now? Organic life, let alone machines, can't survive escaping the sun's influence. So when humans eventually try to make the trip beyond the heliopause, would they suffer the same fate as our unmanned probes, never to be heard from again? Suspend disbelief a moment longer and take a look at other impacts this would have. Obviously, interstellar travel is out of the question. Nothing gets out, but that would also mean nothing is getting in either. I won't go into great detail about this aspect, but it would mean that if there is any extra-terrestrial life capable of visiting Earth, it would have to come from within our solar system. Wouldn't it?
This brings me to my final and probably most important point. Where do we go from here? We could certainly colonize other planets and their moons here in our own solar system, but then we only paint ourselves into a corner. Eventually the sun will burn up most of its hydrogen fuel and expand to nearly ten times its current size as a red giant, swallowing up most of the inner planets before finally shedding its outer layers and shrinking to a white dwarf. If any trace of human life survives long enough to get that far, life will assuredly be much more than just difficult. No, it's my belief that if this theory is correct our only option would be to travel outside of our system through other means. I'm of course talking about other dimensions, worm-hole travel, and other theories such as these.