Radar was invented over 70 years ago. Although it has been greatly improved, the basic concept is still the same and nothing revolutionary has been done. The invention of stealth plane is an example. The way how radar works can be easily exploited by the shape and even the material of the aircraft. Sometimes when an aircraft is flying too low it can also avoid radar detection. However, since more and more countries are working on stealth planes, ex: Russian T-50, Chinese J-20 and J-XX. Eventually everyone will have them. Wouldn't it mean nobody can detect anyone at all by then if everyone still use radar? Is there something new in the development can detecting stealth planes?