thpr writes "New Scientist is reporting on 13 things which do not make sense. It's an interesting article about 13 areas in which observations do not line up with current theory. From the placebo effect to dark matter, it's a list of areas in need of additional research. Explanations could lead to significant breakthroughs... or at least new and different errors in scientific observations. Now there are 20 interesting problems for Slashdotters to work on, once you combine these with the seven Millennium Problems!"