The universe can be mind-boggling at the best of times and a lot of its explanation you just kind of have to accept than attempt to comprehend it lest you turn your brain into rice pudding.
If you've ever tried to learn about quantum mechanics, for example, chances are your lecturer or whatever wikipedia article you stumbled upon probably started with FORGET EVERYTHING YOU KNOW ABOUT LOGIC AND REASON. Even if that warning doesn't put you off trying to understand the immensely complicated world around us, then good luck when you get to Special Relativity: There's no such thing as space and time? They're just... one... thing? WHAT.
While the cleverer people in the world have managed to get past these barriers and have been able to make sense of a lot of the crazy space jargon, there are still a number of things in the universe that scientists still haven't got an explanation for...
10. The Fermi Paradox
We've all fantasized about the idea of other worlds with other lifeforms living fun alien lives and some even believe they've had an encounter with extra-terrestrial beings, most of which are really into probing for some reason.
Outside of the conspiracy theories, there's no evidence that these intergalactic space perverts actually exist but there's a wealth of evidence that would suggest life has to exist elsewhere in the universe, and that is exactly what the Fermi Paradox explains.
Named after Italian-American physicist, Enrico Fermi, it puts together that there are billions of galaxies in the universe and there are billions of stars in each galaxy, most of which will have at least one Earth-like planet orbiting around it and therefore, just by sheer probability, must have something living there.
Many of these stars will be much older than the one we're currently in a very one-sided relationship with, which would suggest that the life on those planets would have developed far sooner than that on Earth, and surely have the means to complete interstellar travel.
Despite the seemingly impossible chance that we are all there is, we still have no hard evidence that there is anyone else and no-one really understands how or why.