Renowned science writer Arthur C. Clarke once said, "Two possibilities exist: Either we are alone in the universe or we are not. Both are equally terrifying.". It has been said that If life can exist and persist in seclusion and in some of the harshest conditions on Earth, it's likely that other interplanetary lifeforms have evolved and acclimated to conditions in space, too.
In more simpler words, the term "Alien" is used to reference all manner of life resident in places other than on Earth. Having said that, there is currently no detailed consensus on the definition of "life". It is a very complex concept. But if we found something like bacteria somewhere other than on Earth, this could be classified as alien life, however it remains to be seen whether this life is like bacteria, or is an exciting "technologically advanced civilization" that can be communicated with.
It is believed that the universe contains hundreds of billions of galaxies, each of which can be composed of up to billions and billions of stars. Most of these stars have at least one planet each. These planetary systems form out of a rich mixture of elements, including all the elements regarded as essential for "life". So, it is hard to believe that the particular mix of conditions that resulted in "life" only occurred on Earth, and not on the trillions of other planets in the universe.
The question that therefore beclouds the minds of many posits thus: Are Aliens real? Well such answer is quite unknown to anyone as Outer space is a vast expanse that we have so much more to learn as Several discoveries and theories from some of the greatest minds in science point to the likelihood that there's something beyond us in the universe, so there's a pretty decent chance we have neighbors somewhere in the outer confinements of earth. Which is why it's hard to flat-out or deny the possibility that other intelligent lifeforms exist. However certain evidences and discoveries over time have seemed to point to the possibility of such been in existence.
On November 14, 2004, a training mission near San Diego became one that well known Commander David Fravor is said to never forget. Fravor recalls seeing a Tic Tac-shaped object that moved much faster than the capability of any known weaponry that currently exists. In a report , it was stated that Fravor and the other pilots saw something strange: what appeared to be a sunken plane or submerging submarine moving erratically right under the water's surface. "It's white, it has no wings, it has no rotors, I go 'holy, what is that?'" Fravor said. The UFO had no windows, and it's reported that infrared monitors failed to pick up on any exhaust fumes. Fravor says it wasn't long before his curiosity got the best of him and he decided to get a closer look. As Fravor began descending toward the water, the craft surfaced, rapidly ascended, and began mirroring Fravor's flight pattern. Then, in an instant, it zipped past the nose of Fravor's jet and disappeared. When Fravor and the other pilots got back to the Nimitz, they shared their experiences with the rest of the crew.
In November 1944, several members of the U.S. Air Force saw what would come to be known as "Foo Fighters," a name borrowed from the "Smokey Stover" comic strip. The Foo Fighters were described as a type of mysterious aircraft that glowed red and could zip and turn through the skies with incredible ease. The first person to spot the lights was Lt. Fred Ringwald, who happened to be a passenger in a night fighter that was flying over the Rhine Valley. The airmen reported seeing between eight and 10 of the aircraft lined up in a row. Concerned that it might be enemy aircraft, the group checked with ground radar, who hadn't registered any odd activity. One of the pilots turned his aircraft around in preparation for a fight, only to find the lights had vanished as quickly as they appeared. The sightings didn't stop there, though. In mid-December 1944, a different pilot saw what was described as flashing red and green lights that created a T formation, which also disappeared as quickly as they came. Several more sightings ensued, and although people tried to come up with explanations for them—the airmen were suffering from "combat fatigue," the lights were a result of some kind of weird weather phenomena, they came from some new, groundbreaking Nazi technology—they still remain a mystery.
Seth Shostak, the senior astronomer at the SETI Institute stated explicitly in an interview thus: "30 years ago, we had not discovered a single planet outside our solar system. Now we know of more than 3,000 of them, and we know nearly every star in the night sky has at least one planet in its orbit. "Even people who are not terribly interested in science know that we've found that planets are as common as fire hydrants, they're everywhere," .
Recent study of other planets and moons in the solar system shows that many worlds possess the ingredients necessary for life, an atmosphere, organic compounds, liquid water, and other necessities. (The moons orbiting Jupiter and Saturn, for example, feature whole subsurface oceans). And even though these places are extremely harsh environments, that doesn't mean as much as we might once have thought it did.
It is important to note however that for Life to exist and be fully formulated there are three basic requirements which includes: Matter, Time and Energy.
• Matter simply refers to the stuff life is made of, the building blocks. These are the chemical elements, hydrogen, oxygen, carbon, nitrogen, and so on. These elements exist everywhere. They're created as byproducts of fusion , the ash of nuclear fires which burn in every star.
• Energy: It has been said that All life feeds on energy. Energy forestalls the natural tendency towards disorder. Any time order is created, such as in growing a body, energy must be expended.
• Time: After the formation of Earth, it took a few hundred million years for life to appear. Several billion more were needed to evolve multicellular life. It took a total of 4.3 billion years to get to mammals, and 4.5 billion to yield a tool-making civilization.
In summary it can be deduced from the above that to progress through these stages there's a need for an environment that remains stable for long periods. So, perhaps, the more expanded answer is we do not know. In fact, we may never be able to definitively answer this question. But of course, there is much work being done in an effort to figure this out. Perhaps one day we can know if we have nearby inter-planetary neighbors, or if indeed we are alone, perhaps we never will.