On Mon, Sep 3, 2012 at 10:28 PM, Giovanni Santostasi <[email protected]> wrote: > Technically a massive or a charged object moving in a circular path should > emit radiation, gravitational or electromagnetic. > > The gravitational radiation emitted by a planet is extremely small so the > energy loss is not going to affect the orbit dynamic even over enormous > period of times. In certain systems where the gravity involved is much > higher (very close neutron stars binary systems) though the energy loss > would make the orbit radius smaller and smaller with time (until the objects > actually collide). > > A classical electron should emit a lot of radiation orbiting a so high > velocity around the nucleus of an atom and should collapse into the nucleus > in a very short time. > This doesn't happen and it puzzled the scientists of the early 20th century. > Eventually quantization of the electron orbits was used as a way to solve > the problem, but it is a unsatisfactory solution because basically it makes > an axiom what is not explained (that certain orbits are allowed around he > atom and they are stable per se). > > I never heard a very good explanation of why this should be true, even > thinking about the electron as a distributed charge over the entire orbit is > not really a very good explanation. > It is an unresolved problem in modern physics. > > But yes in classical physical at first approximation a neutral object moving > in a circle in a central gravitational field does no work because is moving > perpendicular to the force at any moment. >
But that depends on a narrow definition of work which is the acceleration of a mass in the direction of a force. Instead let us say the electron (or perhaps the atom as a whole) does work by supressing the emission of radiation. How much energy is required to suppress the emission of radiation? I suppose it takes the same amount of energy as the difference between energy levels. harry
