 Lord Kelvin (1871) and Carl Anton Bjerknes (1871) assumed that all bodies pulsate in the aether.This was in analogy to the fact that, if the pulsation of two spheres in a fluid is in phase, they will attract each other; and if the pulsation of two spheres is "not" in phase, they will repel each other.This mechanism was also used for explaining the nature of electric charges.