Is there any real evidence to prove or disprove the existence of alien civilizations? Is there any real proof that alien civilizations exist in outer space? What if someone were to say that Earth is the only inhabited planet in the whole universe? How would you respond?

I need to write a five-paragraph argumentative essay to prove that alien civilizations exist. I need to write an introduction, three paragraphs supporting my statement that aliens exist, and a conclusion. In each of the three "body" paragraphs I need to describe in detail a piece of evidence supporting my claim.

I don't even know where to start. I mean, I want to find out the opinion of some scientists who think that we are alone, and then disprove their claim in my essay. I need to know the latest scientific evidence on the existence of alien civilizations. I don't mean like alien abduction stories or any of that science fiction stuff. I need some real proof that will be convincing and not undermine my argument. 

How can you know for sure if there are alien civilizations in outer space? What do they look like? On which planets do they live? What kind of technology do they use? Why are we not alone in the universe? What evidence disproves the claims of Earth chauvinists?
Is there any REAL proof that alien civilizations exist in outer space?


No.


  What if someone would say that Earth is the only inhabited planet in the whole Universe, how would you respond?


Depends on what their goal is. If their goal is to convince me of that, I'd just try to avoid the conversation. If their goal is to come to an understanding of the current body of scientific knowledge on the matter, I'd talk about how we don't know that that statement is true.


  I need to write a 5 paragraph argumentative essay to prove that alien civilizations exist. I need to write an introduction, 3 paragraphs supporting my statement that aliens exist, and a conclusion. In each of the three "body" paragraphs I need to describe in detail a piece of evidence supporting my claim.


That will be difficult, given that there is no such proof. Best you could do is argue that alien civilizations likely exist, given a certain set of assumptions.


  I don't even know where to start. I mean, I want to find out the opinion of some scientists who think that we are alone, and then disprove their claim in my essay.


That is not a good goal for an essay. Don't start with the goal of disproof. Start with the goal of understanding.


  I need to know the latest scientific evidence on the existence of alien civilizations. I don't mean like alien abduction stories or any of that science fiction stuff. I need some real proof that will be convincing and not undermine my argument.


Look at the Drake Equation and recent research that concludes that there are many planets in the galaxy.


  How can you know for sure if there are alien civilizations in outer space?


You would need observational evidence.


  What do they look like? On which planets do they live? What kind of technology do they use?


All unknown.


  Why are we not alone in the Universe?


This question presumes the conclusion that we are not alone. We might be alone.


  What evidence disproves the claims of Earth chauvinists?


None.