From the composition of the universe to why giraffes have such long necks these are 25 unsolved scientific mysteries that will leave you scratching your head. https://twitter.com/list25 https://www.facebook.com/list25 http://list25.com Check out the text version too! - http://list25.com/25-unsolved-scientific-mysteries-that-will-leave-you-scratching-your-head/ Here's a preview: What is the universe made of? Why do we dream? Why do we even sleep? Where do we put all the carbon? How do we get more energy from the sun? What's up with prime numbers? How do we beat bacteria? Can computers keep getting faster? Will we ever cure cancer? When can I talk to my robot? What's at the bottom of the ocean? What's at the bottom of a black hole? How long can we live? How do we solve the population problem? Is time travel possible? Why do we yawn? Why does the placebo effect work? Why are 9 out of 10 people right handed? What causes rocks to sail across the desert floor? How do birds migrate to the same area every year? Even crazier, how do Monarch Butterflies know where to migrate? Why do giraffes have such long necks? How do cats purr? Is light a wave or a particle? What causes gravity?