You believe in it or not, the question of the existence of Aliens is debatable since thousands of years.
What is an Alien? Also known as extraterrestrial life, an Alien can be any living being which does not live on earth. Do not confuse Aliens in Hollywood movies; with green skin, big scary eyes or whatever, these are just illustrations. Even a microbe or bacteria is an Alien if it has life and does live on our planet. It is so sad nowadays, when you talk about extraterrestrial life to some persons, they laugh at you because the first imagination they get in their head is the scary creatures in movies. It is better to use the term ‘extraterrestrial life’ than Alien!
We live in an era where Science is a revolution, humanity is continuously progressing in technology, and more new development is arising in the field of Physics, Astronomy, and Astrobiology etc. We have sent many spacecrafts in space, we landed on the moon, we are studying many planets, stars and galaxies, we just sent Curiosity on the Mars, it is crystal clear the more Science is progressing, the more we can have a solid evidence of the existence of extraterrestrial life.
Until now, no solid proof can support the existence of extraterrestrial life in our universe; however, we know there are planets similar like us such as Gliese 581, Kepler 22b, which may have life but unfortunately, they are too far away. Gliese 581 for instance is 600 years of light away from us. Scientists also believe life could have been existed on other planets in our solar system. Traces of water were discovered on Mars, still here, we do not know if life was present on Mars billions of years ago which could be, and also if some microbes still remain. In addition, many researchers in the science community such as NASA keep searching for evidences. There is also the Search for Extraterrestrial Intelligence (SETI) and other organizations to search for Aliens.
With such a huge and expanding universe, it is absolutely absurd to believe we are alone! We have stars more than the grain of sands on our beaches in the universe, some Physicists believe we have multi-universe. You can ask but how life may exist on other planets? It is simple! Everything began from Big Bang; life could have been developed on other planets just like we had been developed billions of years ago. Planets which do not have enough resources to develop life such as water; this is why on some planets life could not be formed. Natural disasters also play a negative role, such as on Jupiter, Neptune etc… Moreover, if you believe in the theory of Panspermia, life could have been transported through comets to other planets.
And now, suppose there are Aliens on other planets in our universe, are they advanced? Do we have many civilizations also? Have they visited earth before? Are they still visiting earth? Well, the list of questions goes on… Theoretical Physicists like Michio Kaku and others strongly believe if there are civilizations on other planets, no doubt they could have been developed billions or millions of years before us. In fact, perhaps there are other civilizations which have been developed after us as well. Apart from that, probably we have been visited by extraterrestrial beings and are still being visited. The evidences are so strong to not believe a civilization has visited us long time ago. Many conspiracies also contribute that we are being visited by Aliens, and perhaps they are communicating to us, like the government! Thousands of Unidentified Flying Objects (UFOs) are reported each year, about 80% have been debunked but the rest still have no explanations. Many pilots, astronauts, ex CIA members, scientists, and much more have revealed the existence of Aliens and our relationships with them, they have gone further to declare how governments are covering the matter.
We live in a mysterious universe, believing in extraterrestrial life has nothing to do with science fiction novels or movies or even religions. The facts are here, based on a scientific school of thought, we are not alone!