How likely is it that there are alien civilizations in outer space? If they do exist, how did they originate?

 

We don’t know what the future holds for our species; if we or our descendant civilization exist for tens of thousands or millions of years, it’s possible that living on planets orbiting stars might, at some point, become obsolete. We might live some other way, perhaps just in space somehow. If we ever discover aliens, they might not need planets.

We know only one type of life on Earth, and we can only intuit that the first cells emerged similarly on other terrestrial worlds. Therefore, if aliens exist, they must have evolved similarly. Simple cells might have arisen in hydrothermal vents, and the first multicellular lifeforms might have existed in oceans. Aliens should also be terrestrial forms of fish-like ancestors that ventured on land 400 or so million years earlier.

Maybe multicellular, complex creatures must emerge on worlds orbiting stars similar in mass to the Sun. These systems have a limited lifespan before the star swells into a red giant that can engulf and destroy inner planets in its habitable zone. Aliens would know about it, and there might be no point in continuing to live on only their home planet, which is doomed to be destroyed, just as Earth will be engulfed by the hellish fires of our Sun in 4.5 billion years from now.

At a certain level of scientific sophistication, civilizations might establish space colonies in rotating rings that simulate the gravity of their home planet. Finding other worlds on which aliens would weigh similarly to where they came from might be difficult. This is the case in the Solar System, as the best planet we could ever colonize is Mars, but it might be too dangerous for us to live there for long, with just 38% strength of the Earth's gravity, and terraforming this red planet will never fix this issue beyond making the atmosphere more livable.

This is why terraforming worlds might be a waste of resources, and it’s just better to build habitats in space. At some point, aliens could be born in space for generations and forget their origin on a terrestrial planet. They can then more easily embark on traveling across the universe in their space homes, and this might also be our future. Who knows?

Do you believe alien life is possible?

 

The universe hold countless stars and billions of galaxies. Our galaxy holds about 100 to 400 billion stars and the possibilities are endless. But essentially, the whole galaxy and universe wasn't made out of countless galaxies and stars just for a tiny blue planet to have life, alien life must exist but just haven't found it yet when we haven't done anything to figure out how to make faster than light travel across star systems. While we don't have much definite evidence, it's more than likely.

But it's only in out imaginations to wonder what's alien life is but as primitive as we are, we could likely never find out the mysteries of an uncaring spacetime continuum. But our concepts for alien life is astrobiology in hopes of thinking how they might appear according to our understanding. For the record of how big the universe is

Since the expansion of the big bang 13.8 billion years ago, the universe has been continuously expanding due to dark energy and the observable universe is all that we can see, the light hasn't had anytime to reach us and likely never will. Despite this, it's obviously plausible for more galaxies or cosmic filaments to exist beyond this to contain much more extraterrestrial life, medium possibilities for more higher advanced civilizations than us.

But if our universe is infinite, we could never observe anything beyond of what we can currently see but still holds the possibilities of things yet to be imagined.

But yes definitely, we haven't found yet :)