As science progresses, more and more secrets of the universe are being revealed. It's spectacular how much we have figured out, and how far we've progressed from the cavemen we used to be in a cosmic blink of an eye. But no matter how much we learn, there will always be plenty of questions, some of which are surprisingly simple and fundamental, that science has no answer for. Curiosity is a basic trait of mankind, but the fact that we will never know everything carries beauty in and of itself. Here are 21 things that science still doesn't, and might never have an explanation for. 

We spend almost one-third of our lives sleeping, and every single person knows the terror of looking over at their alarm clock and realizing they need more. Yet for something that has such a tangible impact on our daily lives, its true purpose and processes are unknown. Only recently have scientists started to actually uncover what is going on when you drift off, but they have a ways to go. 

The brain itself has always been somewhat of an enigma, and the origins of consciousness and life may never be truly understood. But for that, we have philosophers and poets. Here are 21 things science has no explanation for.