13 things that do not make sense

http://www.newscientistspace.com/article.ns?id=mg18524911.600
interesting article about some things still confusing current scientists
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