Can a chicken egg be successfully hatched on a heating pad rather than in an incubator?
No because an incubator does more than just keep the egg warm. It keeps the eggs at a certain required humidity level. You need the right heat and humidity to hatch an egg. It will just dry out as it forms without it. Most incubators have water troughs or reservoirs with a wick in it, tied to a wet-bulb thermometer to tell you the right humidity. And you also need to turn the eggs gently with regularity, another thing that most incubators do for you.
