Early 21st century science has detected many Earth-like solar systems, some with non-gaseous worlds that could support life. Even our interplanetary probes and other scientific methods have detected water on the moon, Mars and on Jupiter's moon Europa. If water is in our own solar system, the mathematical odds are that it exists throughout the universe in one form or another. Under the right conditions, intelligent life should exist in one form or another. Some intelligent, non-humanoid life forms may not even rely on water, oxygen or other sustaining means.
There is no conclusive proof of intelligent life forms elsewhere in the universe-in the eyes of hard-core, prove-it-to-me conclusively science. But even saying that, the most ardent, "humanistic" scientist knows that the mathematical probabilities say they exist. They just say they've never been to the earth due to the fact that the speed of light could never be exceeded, for it would take more energy than in the entire universe to do so. Already, there is some early scientific data to suggest that the standard of not being able to exceed light speed is poised to fall. Even Einstein hinted to the possibility that light speed could be breached by saying that if one breached light speed, he or she would automatically go back in time. What if the speed of light was broken in such a way that an object exceeding it would not require more energy than the universe could muster to be able to traverse the distances. it's also possible that space and time could be "bent" by alien species to traverse such great distances.
Science cannot conclusively prove the existence of quantum realities. But science now says that these realities exist and other realities are there, possibly coexisting within our own. Certainly, science fiction writers and mystics have been saying it for generations-the mystics countless generations. Within several more decades scientists could prove that they exist. Science fiction writers wrote about other "dimensions" and "parallel universes", peopled with intelligent beings, and humanity traversing back and forth between them. The popular Star Trek spinoff, DS9, was centered around a 'wormhole' between extremely vast parts of the universe. As they say, science fiction always predicts the future.
Science fiction writers have been writing about a well-inhabited universe for countless years. Sci-fi writers seem to be part of a collective consciousness that is plugged almost into a "universal matrix" of knowledge. As technology moves at an exponential curve upwards, the hard proof will come. Unless these alien beings openly declare themselves first...After all, many say that the earth has been visited by beings from other planets and dimensions for many millennia. Although many scientists will openly scoff and ridicule such an idea, some skeptics will say it's possible they've been here in ancient times...but not in modern times. But with the extreme vastness of the universe, the strong possibility of interdimensional and wormhole travel, comes the reality that not only do other beings exist in our universe, but that they have been visiting us on and off, not just in the past but the present as well.
With more advanced technologies coming rapidly that will enable science to "see" distant worlds through more advanced telescopes, the reality of seeing water-borne planets, with vegetation, like Earth is becoming increasingly closer everyday. Such telescopes may even detect artificial lighting on such Earth-like orbs. But there are still many unanswered questions about the earth's own solar system, with possible ruins on the Mars and Moon. Even the so-called "conclusive" proof of life not existing on Mars in the form of the famous "face" on mars, through the more highly-resolved orbital photo, still shows highly prominent lines that have sharp, artificial-looking edges. These lines constitute the outline of the face, or some kind of helmet.
But still that is conjecture and not proof-although something very intriguing and mouth-watering for those with open eyes Perhaps very soon science will have the answers. The recent discovery of the planet Gliese 581 C, in the so called "Goldilocks zone" in habitable zones of not too hot or cold-a planet with liquid water. Computer models predict either a water borne world or a rocky planet like Earth. This is the first significant breakthrough in the discovery of planets harboring water, and therefore life-aka the "habitable zone". This is hard science-and the tip of the iceberg in many stunning revelations to come.