This means that, except in the case of very small, very young sources, we cannot observe radio source dynamics directly, and so must resort to theory and inferences from large numbers of objects.
Isto significa que, agás no caso de fontes moi pequenas e moi novas, non podemos observar a dinámica da radio fonte directamente, e debe recorrerse á teoría e a inferencias a partir de gran número de obxectos.