Lately, the one question on my mind related to Alien Realities is "should we actively try to make contact with other planetary civilizations?" IF distances between solar systems are such that viable physical travel between them is virtually impossible, then there is little physical danger and thus, little reason to fear contact. Psychological, sociological, theological, and cultural dangers are another topic - we don't need physical contact to still be affected. Many scientists so far say interstellar travel is highly impractical: the energy costs are enormous (maybe close to infinite) and the time needed generational. Also, the speed of light does seem to be ultimate speed barrier, and there are no workarounds that seem viable. For instance, many feel that wormholes are not a viable workaround, despite what one my favorite Sci-Fi series uses for their main means of interstellar travel - as they would require far too much energy, and can not be controlled. But just because we can't see any viable "workaround" at present doesn't mean there are not any.
There are other assumptions at work here as well: what may be a generational travel for us (would take many generations of people to get there) may not necessarily be a generational trip for an extremely long lived alien species. They may not mind the long separation from loved ones (if they even feel such emotions, or have such emotional equivalents).
Also, in such a large universe, could there not be a species that is so xenophobic for whatever reasons (even reasons that may not make sense to us) that they are willing to send out a barrage of weapons toward our planet at the first sign of our existence? The weapons may take hundreds or thousands of years to reach us, but that doesn't make it impossible for a alien society from launching them. On the other hand, if they are that xenophobic, launching an attack would broadcast their presence, and they would need to ensure that their weapons could 1) approach completely undetected and 2) completely destroy their target - otherwise a retaliatory response could be mounted against them. Though as we see too often with our own species, intelligence and wisdom do not always go hand in hand - there is no reason to assume alien species would always have increased wisdom with increased intelligence or increased knowledge.
I think we have to be very careful. The old Bugs Bunny cartoon where Marvin the Martian cavalierly wants to destroy the Earth because it gets in the way of his view of Venus could have a kernel of chilling truth to it.
"Where's the Kaboom? There's supposed to be an Earth-shattering Kaboom?" - Marvin the Martian.On such an uplifting note I will leave for now, but shall return to this topic from time to time.