Enrico Fermi (Nobel laureate in physics) insisted that there were aliens among us. He called them Hungarians.
Beyond that, the probability of contact with an alien civilization is diminishingly small. Consider that only once in the 4.3 billion or so years of the earth's existence has one cell engulfed another and formed a symbiotic union (mitochondria in every eukaryotic cell) and that from this one event has evolved all the visible diversity that we experience (but not bacteria nor Archaea), which are invisible to the naked eye, but which still dominate the balance and ecosystems of our planet. At the same time, consider that human civilization has existed for less than 1/3000 th of that time, and the resources used to visit the nearest planets (Luna and Mars), the closest Earth-like planet (free water, Nitrogen atmosphere), should it support a lifeform with technology similar to ours, which has been emitting radio waves for only about 100 years would need to detect our radio waves, which at most could have travelled 100 light years in order to initiate a response (as we have been looking at red-shifted frequencies using radiotelescopes), etc., etc..
All these things are dependent on mitochondria being able to produce more energy from glucose than can prokaryotes, permitting them to both grow larger cells and to specialize activities among cells, developing tissues and organs dependent on efficient utilization of carbon. A later innovation was the symbiosis of one of the early eukaryotes with a bacterium ancestral to the chloroplast. These organisms can eat light. We call them plants.
Anyway, no aliens here, unless we all are. Crick postulated what he called pan-spermia. Who knows? If the ancestor to all eukaryotes was brought here or created here doesn't matter much. Sorry to rain on your parade.
Beyond that, the probability of contact with an alien civilization is diminishingly small. Consider that only once in the 4.3 billion or so years of the earth's existence has one cell engulfed another and formed a symbiotic union (mitochondria in every eukaryotic cell) and that from this one event has evolved all the visible diversity that we experience (but not bacteria nor Archaea), which are invisible to the naked eye, but which still dominate the balance and ecosystems of our planet. At the same time, consider that human civilization has existed for less than 1/3000 th of that time, and the resources used to visit the nearest planets (Luna and Mars), the closest Earth-like planet (free water, Nitrogen atmosphere), should it support a lifeform with technology similar to ours, which has been emitting radio waves for only about 100 years would need to detect our radio waves, which at most could have travelled 100 light years in order to initiate a response (as we have been looking at red-shifted frequencies using radiotelescopes), etc., etc..
All these things are dependent on mitochondria being able to produce more energy from glucose than can prokaryotes, permitting them to both grow larger cells and to specialize activities among cells, developing tissues and organs dependent on efficient utilization of carbon. A later innovation was the symbiosis of one of the early eukaryotes with a bacterium ancestral to the chloroplast. These organisms can eat light. We call them plants.
Anyway, no aliens here, unless we all are. Crick postulated what he called pan-spermia. Who knows? If the ancestor to all eukaryotes was brought here or created here doesn't matter much. Sorry to rain on your parade.
