Why fresh eggs sink in water and old eggs float?

One Answer: If one egg is rotten, the rotting creates gas inside the egg, which makes it float. That is one way to test whether an egg is good to eat or not. If it floats, trash it. There is an air pocket on the fatter side of the egg. The older egg gets the larger this bubble becomes. Making it more buoyant. When an egg is bad they will float so beware when you crack them.