13 Things We Can't Explain

Even with all of our science and research capabilities there are things we simply cannot explain. Here are 13 mind benders that have been puzzling the science world. 1 The placebo effect 2 The horizon problem 3 Ultra-energetic cosmic rays 4 Belfast homeopathy results 5 Dark matter 6 Viking's methane 7 Tetraneutrons 8 The Pioneer anomaly 9 Dark energy 10 The Kuiper cliff 11 The Wow signal 12 Not-so-constant constants 13 Cold fusion