There are several reasons for eggs to break when you boil them. The rumor I hear most frequently is that placing a cold egg in boiling water will cause it to break. I've been starting my eggs in boiling water for several years now and don't find I have anymore casualties than when I started them in cool water.
Upon close examination, I found, that the eggs that broke, had shells with small barely visible imperfections. Those weak spots will break regardless of water or egg temperature. Take a look at our video. I think we may convince you to start your eggs in boiling water. To make the perfect hard-boiled egg, you need to control time and temperature. Starting them in boiling water is part of the temperature control.
At sea level, you can count on boiling water always being 212 degrees Fahrenheit. Boiling water will not get hotter, no matter how much you crank up the heat. Instead it will turn to vapor (steam}. It may boil faster, but it will never get any hotter. I have always found this fascinating. Go figure!! Take a look at our complete hard-boiled egg recipe.