Well you and ever other living creature on our planet is a perfect example. The fact that 7 billion fellow human beings are alive proves that life has the potential to pop up in our universe. So If life has the potential to grow here on Earth, doesn’t that mean it can happen somewhere else?
Maybe on a planet that is part of another solar system or maybe even the moon orbiting that planet. For life to flourish on Earth we need water, so if we can find water on another planet there is a chance that life as we know it could be there.
Like Jupiter’s moon Europa. This moon is believed to have a whole ocean beneath its surface. Meaning that alien creatures could be swimming around right know without us even knowing about. Of course this is only a theory and we are not going to be able to travel to an Aliens world anytime soon to investigate.
But what if there was an alien race out there that had the technology and knew how to travel to Earth. What if they came down from the heavens, landed, opened there space craft and walked out on to our planet. Proving that life is able to flourish else were in our universe. How would we react? It would without doubt change our lives for ever.
The religious parts of the world would be affected by the news massively, as It would basically prove their religion wrong. However some religions are more accommodating to the idea of aliens than others. Certain Christians, for example believe that the Earth was literally created by God in six days some 6,000 years ago and that humans descended from Adam and Eve with the original sin.They could very easily except that life could exist on other planets, believing for example that beings that didn't descend from Adam and Eve on Earth wouldn't be inherently sinful, and effectively, they wouldn't need Christianity to be saved.
Many people whether they are religious or not might choose to deny the existence of alien life, but many others would feel proud to witness human history right in front of their eyes. However most of the world would probably just be shocked,not knowing what to do. Society as we know it may break down and our world would change for ever.
The world may collapse in to fear as the governments try and prepare a plan of action. Extra-terrestrials might not be that different from us, such as greed, violence and a tendency to exploit others' resources. Which would mean bad news for mankind.
Orson Welles infamous radio broadcast of War of the Worlds in 1938 caused mainstream public panic as people acted to protect there selves, so a televised broadcast of alien contact could cause world wide panic. However if the alien race came in peace, then we as the human race may welcome them. We have been fascinated with E.Ts for thousands of years, many people have looked to the skies and thought that they had experienced something out there. There is, it seems, a deep human craving that we aren't alone, and that could be a significant part of our response to meeting an alien being.
So maybe one day, in the not so distant future mankind will meet or at least discover another world of beings. Whether it will be for the good of the human race or not, we will just have to wait and see.