Most of what you say I agree with. Given the Big Bang theory, it is clear all things (energy or matter or both) were created at the "same" time. In order for a planet to form, a Sun/Star must exist first to be the furnace that takes in fuel of some kind and generates the heavy elements that exist on our Periodic Table. We have seen stars die, but we have never seen one born. We know that early physicists theorized that gravity would eventually slow the expansion of the universe and then force it to contract. Yet physical observations using the Laws of Planetary Motion clearly show that not only is the universe not slowing down or contracting, the expansion of the Universe is "accelerating. One day our descendants will look up to a sky with no stars, planets, galaxies, or nebulae. So the 4.3 light years will grow overtime. Given the young age of the universe, deadly loose particles/waves (radiation) exist throughout the universe. Tests have proven that short term presence in our local space have many detrimental biological effects and potentially more over a longer period of time. This happens in the absence of dense radiation fields we would encounter on a long journey (4.3+ light years) outside our planetary system as well as moving physical objects (rogue planets, asteroids, comets, stars and others) in our path. To survive such a journey you must have impenetrable shielding, an infinite oxygen supply, food, fuel, and artificial gravity at a minimum. Are there systems out there that have existed long enough since the Big Bang to create beings that can overcome such major obstacles?My Dad was a Meteorologist for 34 years from 1942 till 1976 in southern Indiana. I remember going out to the airport where the weathermen would launch rather large balloons where they would then TRACK the balloon with a small telescope to calculate the wind direction and approximate speed. I always wondered if what we saw back them were weather balloons. As the climbed into a less dense atmosphere, the would expand getting much larger until eventually bursting. As to alien beings, my take is they would have to be animate creatures with a "life span". The vastness of space would virtually preclude anything LIVING long enough in the time frames required for s[ace travel to make it to Earth. At the speed of light, the next nearest star is 4.3 LIGHT YEARS away. None of our other planets in our solar system seem capable of sustaining any life forms of which we know. Very interesting subject, though.