This might seem simple... I'm having a bit of trouble both finding and interpretting information on how a gravitational wave is produced. I know they are analogous to EM waves, and that they are produced by accelerating masses, but it's more complicated than that, isn't it? Can anyone explain to me what a quadrupole moment is, in layman's terms preferably? How does a binary star system (such as PSR B1913+16) emit gravitational waves? How does it produce an alternating gravitational/gravitomagnetic field, since gravity is never repulsive? If you could explain everything in classical physics, that'd be great too. Thanks alot in advance.