Simple math shows how many space aliens may be out there
Yes, there may be a mind-boggling number of habitable planets out there, and based on an estimate of the likelihood that a habitable planet may produce and sustain a technological society, there may be 10,000 such societies in our own galaxy, and scientists estimate there are at least a hundred billion galaxies.
... even the mammoth number produced by that multiplication is less mind-boggling than the sheer vastness and emptiness of space. A few simple calculations lead to an estimate that the nearest technological civilization is likely to be at least a thousand light-years away. "Today's fastest rockets would take at least 20 million years to get there, by which time you're going to be awfully tired of on-board pretzels."
The universe undoubtedly includes many civilizations. But few, if any, are close enough neighbors to visit one another. It is possible for a single star to be surrounded by multiple habitable planets, in which case it is possible (maybe even likely) that existing somewhere out there are civilizations from different planets who have met one another. It does not seem that we will ever be one of those civilizations unless it is possible to conquer the light barrier.