Want to know which eggs in the fridge are raw and which have been hard-boiled? If you spin one on the counter, the hard-boiled egg will spin smoothly and quickly, rather like a top. The raw egg, on the other hand, will wobble and spin more clumsily. The reason for this difference is that the inside of the hard-boiled egg is solid, so it all moves together as one entity. The inside of the raw egg, of course, is a liquid blend of yolk and egg white, which are all swirling at the same time. Because the yolk and egg white have different densities, the raw egg will wobble in a decidedly side-to-side, uneven motion.
What to look for in an egg: