If we are to use the methods of physics, we can prove that the space aliens cannot come from anywhere but here and they are us if they are anything real.
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Some interesting probably useful points.
However, in the above sentences, evidently there are some assumptions that are laughable from the ET's perspective. They have been queried on such by a number of folks and the persistent response is bemusement over our inadequate understanding of reality.
Of course they are amused rather than bemused. They are us but equally do not know this any better than we do.