Scientists still aren't sure why we sleep. Some believe it's to regenerate cells, others to solidify memories and learning, but various studies prove each theory to be questionable. Does that mean one day we won't sleep at all? Imagine how much more work we'd get done! And by work, we mean watching panda videos on Facebook.
Humans have played some kind of music for at least 50,000 years, but why? Some historians believe that it brought people together and was an effective way to control people (think about ritual drumming and military music). This theory, however, can't be proven, so we have to make up our own minds!
Over 100 cases have been reported of people randomly bursting into flames. Scientists believe it could either be due to deep cigarette burns that turn body fat into fire, or methane gas in the intestines react and create fire. They can't be sure of either though as they can't test them out by scientifically setting fire to people!
It's a common occurrence for patients given placebo (fake) pills in drug trials to feel whatever their condition is improve. There are a number of theories to explain this but none are proven. Is illness psychosomatic? Or does this happen by chance?
Some say it's to get more oxygen into the body when we are lacking it, others to cool and optimize the brain. So why are they contagious? Perhaps it's to show compassion or maybe it's because we're all just plain bored!
Humans measure existence through time and space with three dimensions: longitude, latitude and time. However, some theorists believe that there could be anywhere between four and eleven right here on Earth, but we just can't see them. Until someone manages to visit one of these dimensions, though, we'll just have to stick with what we perceive as reality!
Ok, now this is just getting ridiculous! Surely it's slippery because...well, wait. This is trickier than we anticipated. Apparently, it could be due to a thin layer of water on top of the ice, but you don't slip on a damp sidewalk, do you? Well, maybe you do. Either way, we're lost and so is science.
This one always sparks heated debates! Although believers would say there is a ton of video, photographic and retold evidence, none of this seems to be enough to solidly convince science. Logical thinkers like to explain away ghostly encounters, so until they relax and think outside the box, ghosts are apparently "not a thing." Personally, we disagree.
Until we have mastered extreme space travel or made clear contact with aliens, it's unknown. Mathematically speaking, though, it seems extremely likely, considering the number of planets and stars in the universe (that we know of)!
Things just got heavy. There are lots of recordings over the years of animals randomly jumping off cliffs to their deaths and even one of a dog repeatedly trying to drown itself. Scientists can't figure out why they would do this.
Scientists are constantly discovering new species. Granted, by now, they're mostly just tiny bugs that are pretty similar to other tiny bugs, but still, that means we can't say exactly how many there are! Seems crazy not to know who we're sharing the planet with. That's like never knowing who your next door neighbor is!
Glass is made of glass... Stop hurting our little brains! Apparently, though, glass itself is an odd material. It doesn't exactly act like a solid or liquid, especially when transitioning from a molten to a hardened state. Scientists don't know why and we need a nap.
Now, for something a little lighter to calm your nerves. For some reason, mathematicians cannot figure out how likely it is to win at solitaire! Sometimes you win, sometimes you lose and there is no way of knowing the odds. That sounds like a metaphor for life and also a pretty good note to end this list!