13 Things That Do Not Make Sense

New Scientist magazine has a curious little article about 13 things that do not make sense. Read the details of why these things continue to puzzle some rather brilliant people:

1. The Placebo Effect -- your mind really does work in biochemically mysterious ways.
2. The Horizon Problem -- the universe appears uniform, everywhere you look. Yet it it's so large, there is no way energy could travel from one side to the next to make it so.
3. Ultra-energetic Cosmic Rays -- we're detecting some really powerful particles hitting the Earth from outer space. Only problem is, we can't find the source.
4. Belfast Homeopathy Results -- homeopathy works, and no one really knows why.
5. Dark Matter -- the galaxy isn't falling apart, so there must be something holding it together. Yet we can't find it.
6. Viking's Methane -- in 1976, the Viking lander detected carbon-14 containing methane in the Martian soil. Signs of life?
7. Tetraneutrons -- in 2002, scientists discovered particles in a particle accelerator that shouldn't exist. Dubbed tetraneutrons, the particles consist of four neutrons bound together, defying the laws of physics.
8. The Pioneer Anomaly -- launched in the early 1970s, the Pioneer spacecrafts are now at the edge of our solar system. Something strange is happening however. The spacecrafts are either being pulled or pushed by some unknown force, making them speed up.
9. Dark Energy -- the expansion of the universe is speeding up. We don't know why. Let's invent something we can't see to explain it.
10. The Kuiper Cliff -- after passing Pluto in the solar system, you enter the Kuiper belt, filled with remnants of the formation of the solar system -- icy rocks mostly. The Kuiper belt however, ends rather abruptly. Why? Is there another large planet out there?
11. The Wow Signal -- in 1977, we recorded 37 seconds of a radio signal from the direction of Sagittarius. Was it ET? No source for the signal has been found.
12. Not-so-Constant Constants -- the laws of physics employ a whole lot of constants. Were they always the same value however? Or are they changing over time? Observations from deep space suggests the constants aren't really constant.
13. Cold Fusion -- yes, it never went away. Is it possible?