Scientists are wonderful people. It takes a special mind to be able to not only exist but thrive at the border of what is known and unknown. Most of us exist well inside that border, comfortably shielded by textbooks and teachers who give us the answers. But just because we can exist comfortably at that boarder of the unknown doesn't mean we necessarily have "all the answers." Indeed, scientists are always stumped by one problem or another and even those problems that they discover answers for they constantly revisit to make sure what they think they see is what they actually saw. Then you have things like the Fermi Paradox.
In 1950 Enrico Fermi was asked about the probability of the existence of extra terrestrial civilizations. His answer was simply: "Where are they?" This led to the creation of what is now popularly known as the Fermi Paradox. Enrico Fermi deduced that any species capable of interstellar travel would expand outwards exponentially until it had colonized the entire galaxy. If such a civilization existed then we would surely know about it. So why haven't they visited? The answer of course is we don't know. We didn't know then and we don't know now but that doesn't mean they don't exist. The problem with the Fermi Paradox is that it ignores an nearly infinite number of factors that would prevent any civilization from visiting Earth. I go over a few of them in my video series below:
The Fermi Paradox is so flawed I could spend all day writing about all of them but the number one reason it falls apart in my opinion is that Fermi himself fails to account for one very important fact:
The universe is FUCKING HUGE.
There are approximately 4,500 stars visible all around the Earth to the naked eye. So let's just assume that every 4,500 stars has one planet that hosts intelligent life. There are over 100,000,000,000 stars in the Milky Way Galaxy alone. Do the math and that leaves over 22 MILLION inhabited planets in our galaxy and that's assuming my hasty assumption is even in any way accurate which it most likely isn't. Now why stop there? The universe is host to over 100 billion galaxies. Take that into account and you suddenly realize the universe could hold tens of trillions of intelligent species. When you're facing those kinds of odds the question "Where are they?" just doesn't have any meaning.
The problem with being a human being is that when you don't know something you get uncomfortable about it. This leads to a nasty tendency of just making shit up. In fact it has given rise to a well known psychological phenomena called "Argument from Ignorance." What's that? I don't know, it must be (XYZ) Only slightly less well known is another logical fallacy called "Begging the Question" which is no less flawed and doesn't go any farther than the argument from ignorance in terms of explaining... well... anything. When Enrico Fermi answered the question with "Where are they?" he was begging the question, deflecting the burden of proof and not even attempting to answer the original question. When you don't know something the hardest answer to give is "I don't know" and that doesn't change just because you're a scientist.